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Invasive Plants – an Overview

It’s everywhere! multiflora rose (photo by Famartin)

The United States is overrun with introduced plants. Five years ago, Rod Randall’s database listed more than 9,700 non-native plant species as naturalized in the U.S. Not all of these species were “invasive”.

At that time, regional invasive plant groups listed the following numbers of invasive species in their regions:

Southeast Exotic Plant Pest Council – approximately 400 invasive plants
Mid-Atlantic Invasive Plants Council – 285 invasive plants
Midwest Invasive Plants Network reported that state agencies or state-level invasive plant councils in its region listed more than 270 plant species as invasive, noxious, or pest species
California Invasive Plants Council listed 208 species.
Texas Invasives reported more than 800 non-native plant species in the state, of which 20 were considered invasive.

Species – Rankings and Extents

We know that these invaders are affecting wide swaths of many ecosystems. A recent study based on Forest Inventory and Analysis (FIA) data (explained here) showed that nation-wide, 39% of forested plots sampled contained at least one invasive species. Hawai`i was first, at 70%. Eastern forests were second, at 46%. In the West overall, 11% of plots contained at least one invasive species. Plots in both Alaska and the Intermountain states were at 6% of plots invaded. A different study (Barrett and Robertson 2021; full citation at end of blog) reported the proportion of Western forest covered by invasive plants. This approach resulted in different numbers, but the same general ranking: Hawai`i again “led” at 46%; Pacific Coast states at 3.3%; Rocky Mountain states at 0.75%; coastal Alaska at 0.01%.

In more arid regions, data from the Bureau of Land Management showed that invaded acreage had more than doubled between 2009 and 2015.

buffelgrass removal in Tucson; Photo by Julia Rowe, Arizona Sonora Desert Museum

The situation is expected to get worse: a study of just one small portion of U.S. naturalized plants found that non-native plant species were more widely distributed than native species and that the average invasive plant inhabited only about 50% of its expected range. Furthermore, human actions were more important in facilitating spread than the species’ biological attributes.

Most of the detailed studies have been conducted in the Northeast – by both Forest Service and National Park Service scientists. The USFS’ Northern Region (Region 9) contains 24 states, from Maine to Minnesota, from Delaware to Missouri. A review of forest inventory (FIA) data (Oswalt et al. 2015) provided details on 50 plant species. (Unfortunately, the Southern Region [Region 8] has chosen to report in different formats, so it is hard to get an overall picture of invasive plants throughout the forests of the entire East. This is especially annoying to those of us who live in Mid-Atlantic states, which are divided between the two regions.)

Oswalt et al. (2015) provided data on the percentage of FIA plots in each state that were reported to have at least one invasive plant species. The northern Midwest ranked highest – e.g., one state (Ohio) at 93%; one state (Iowa) at 81%; two states (Indiana and Illinois) above 70%. Parts of the Mid-Atlantic region were almost as invaded – West Virginia at 79% and Maryland at 65%. The Northern plains states ranked lowest in invasions – North Dakota at 29% and South Dakota at 15%.

A study by the National Park Service of part of the Northeast (from Virginia and West Virginia to Maine) found a situation similar to that found by USFS researchers. In 35 of 39 park units, more than half of the plots had at least one invasive plant species when the 2015-2018 survey began. In 10 parks (a quarter of those surveyed), every plot had at least one. Invasions are worsening: 80% of the park units showed there was a significant increase in at least one trend measuring abundance.

Japanese stiltgrass in Shenandoah National Park; Photo by J. Hughes

The USFS and NPS report different species to be most widespread. In the National Park Service-managed units, Japanese stiltgrass (Microstegium vimineum) was found on 30% of all plots, in more than 75% of all NPS-managed units in the study. This magnitude comes despite the species not being found north of 41^o N latitude. In forest plots inventoried by the USDA Forest Service, Japanese stiltgrass was the 14^th most widespread species in the Northern region. I speculate that the species might not be common in the upper Midwest, which was not included in the NPS study. Oswalt et al. (2015) noted that Japanese stiltgrass was the 5^th most common invasive plant in the Southern region.

Both studies agreed that garlic mustard (Alliaria petiolata) is widespread. The NPS study found it to be the most frequently detected non-grass herbaceous species, detected in 20% of plots throughout the study area (Virginia and West Virginia to Maine). On forest plots monitored by the USFS, garlic mustard was the 3^rd most frequently detected species, on 4.5% of the surveyed plots. The species is reported to be present in 36 states & 5 provinces.

Why do Studies Ignore Deliberate Planting as a Factor?

Both USFS & NPS found shrubs and vines to be highly widespread. NPS specified Japanese barberry (Berberis thunbergii), Japanese honeysuckle (Lonicera japonica), multiflora rose (Rosa multiflora), and wineberry (Rubus phoenicolasius). USFS FIA data showed multiflora rose to be the most frequently recorded invasive plant, present on 16.6% of surveyed plots. It is otherwise recorded in 39 states and 5 provinces. Multiflora rose is almost ubiquitous in some states; in Ohio it is recorded on 85% of the plots. “Roses” were reported to be the 3^rd most common invasive plant in the Southern Region. Other shrubs also dominated FIA plot detections: European buckthorn was 4^th most frequently detected species, present on 4.4% of survey plots; or in 34 states and 8 provinces. Its presence is highest in New York, at 16.8% of plots. If the plots invaded by the various bush honeysuckle species do not overlap, these shrubs occupy 9.5% of all surveyed plots – second to multiflora rose. The vine Japanese honeysuckle ranked 6^th – present on 3.6% of survey plots across the region. Japanese honeysuckle is reported to be the most common invasive plant in the Southern region. Other shrubs ranking 12^th or above included Autumn olive and Japanese barberry

Tree-of-heaven (Ailanthus altissima) was the most common invasive tree found in National parks, again, despite not growing north of 41^o N latitude. It is found in 9% of plots.

I will say that I find it extremely annoying that the scientists carrying out these studies never mention that virtually all these shrub species had been deliberately planted in forests or nearby lands! Instead, they focus on such factors as histories of agriculture and other disturbances and fragmentation. It is well documented (e.g., Lehan et al. 2013) that the vast majority of shrub species introduced to the U.S. were introduced deliberately. Furthermore, more than 500 plant species invasive in some region are being sold on-line globally.

Deliberate planting of species that turn out to be invasive is also rarely recognized in the West, e.g., Pearson et. al. There, the motivation for planting might be livestock forage or erosion control rather than wildlife habitat “enhancement” or ornamental horticulture.

I am pleased that the most recent study (Barrett and Robertson 2021) differs somewhat by noting (sometimes) both invasions by forage grasses and the appearance in the mesic forests of Pacific states such planted species as Armenian blackberry. However, while this report notes the potential that pathogens might be transported to new areas by restoration planting and “assisted migration”, it does not mention the concomitant risk of introducing plant species that might prove invasive in the naïve ecosystems.

English ivy invading forest in Washington State; photo from Washington Noxious Weed Board

[Go to the earlier blogs linked here and the Western forests report for discussions of management strategies.]

Annual reports from the NPS Invasive Plant Management Teams (IPMTs; before FY19, “Exotic”, so EPMTs) provide some information about the agency’s efforts to control invasive Plants. Go to Invasive Plant Management Teams – Biological Resources Division (U.S. National Park Service) (nps.gov) . Scroll down to the short paragraph under the heading “Learn about how the teams are actively working …” This link takes you to reports from FYs 2016 – 2018. Reports from FY19 and FY20 will be added soon. Currently at FY 2019 is at https://irma.nps.gov/DataStore/Reference/Profile/2286813 & FY 2020 is at https://irma.nps.gov/DataStore/Reference/Profile/2286814

New Information from Study of Forests in the West

Barrett and Robertson (2021) state that although invasive plants are increasing in extent and intensity in Western forests, they are usually considered to be contributing factors rather than as proximate causes. However, they note two caveats: 1) determining the ultimate causes and resulting implications of these recent increases is more difficult; and 2) data are particularly poor on plant species’ presence. Indeed, the FIA survey process link is ineffective for early detection and tactical monitoring [that is, identifying particular species in specific habitats of concern] of plant invasions.

Of the 23.4 M ha of forested lands that have experienced a disturbance over a five-year window (the time frame for FIA), only 600,000 ha was affected by the combined categories of geologic, vegetation, and other disturbances. (This is 10% of the area affected by either insects or pathogens.) Cheatgrass (Bromus tectorum) was by far the most abundant species in Western forests, covering 480,000 ha, or about 0.49%cover of all forested land in the conterminous Western United States. Because of the difficulties of surveying, Barrett and Robertson (2021) conclude that the area covered by IAS plants on the Pacific Coast and Rocky Mountains could be twice recorded values.

FIA surveys detected the highest number of non-native plant species in the forests of the continental Pacific states — 259 species. Many were grasses (although different species than in the Rockies), but shrubs and other forbs were also present. In the Rocky Mountain states the surveys detected a total of 195 non-native species, primarily grasses. FIA surveys in Hawai`i detected 136 non-native species. The most abundant was strawberry guava, which was detected on 9% of the forested area in the state. Surveys of FIA plots in coastal Alaska detected only 8 non-native plant species; common dandelion was the most abundant. Except in Hawai`i, the plants were expected to have substantially lower impacts than in eastern forests.

I note that the US Geological Service (Simpson and Eyler, 2018) reports there are approximately 1,754 non-native plants in Hawai`i and 424 in Alaska. Not all are necessarily invasive. And the USGS study covered all of Alaska, not just the southeastern coastal region.

Barrett and Robertson (2021) found that plant invasions are less extensive in older forest stands, mesic stands in contrast to drier areas and those with sparse or open tree canopies, and farther from roads. Thus, invasive plant cover was higher in hardwood and low-elevation and dry conifer forest types than in high-elevation and moist conifer types. In Hawai`i, mean plant cover was more than 40 % in all forest types except cloud forest, where it was 7.8 %. Again, proximity to roads was mentioned in the context of the likelihood of disturbance but no mention was made of the fact that households and businesses (e.g., tourist facilities, even agency facilities!) might deliberately introduce plants – e.g., horticulture.

Barrett and Robertson (2021) expect the impacts of NIS plants on forest lands to increase in the future, due to both additional introductions (despite efforts to prevent such) and spread of established species. They note that every disturbance creates an opportunity for the many ruderal and graminoid species to establish – facilitated by their abundance nearby. They note the significant challenge presented by secondary invaders, which often respond to space made available by “weed control” projects better than natives.

I welcome their concern about shade-tolerant plants apparently increasing in wetter areas of the Pacific coast states. They note that the presence of non-native plants in a forest is less obvious, and the impacts might be more subtle, perhaps primarily affecting tree regeneration through competition or other effects (e.g., promoting fire). Barrett and Robertson (2021) note that many of the shade-tolerant non-native species abundant in temperate Eastern U.S. forests (e.g., garlic mustard) are present in the West and are likely to become important.

SOURCES

Barrett, T.M. and G.C. Robertson, Editors. 2021. Disturbance and Sustainability in Forests of the Western US. USDA Forest Service Pacific Northwest Research Station. General Technical Report PNW-GTR-992

March 2021

Simpson, A., and Eyler, M.C., 2018, First comprehensive list of non-native species established in three major regions of the United States: U.S. Geological Survey Open-File Report 2018-1156, 15 p., https://doi.org/10.3133/ofr20181156.

ISSN 2331-1258 (online)

Posted by Faith Campbell

We welcome comments that supplement or correct factual information, suggest new approaches, or promote thoughtful consideration. We post comments that disagree with us — but not those we judge to be not civil or inflammatory.

For a detailed discussion of the policies and practices that have allowed tree-killing pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm (These reports do not discuss invasive plants.)

Tuning in to the News – Mostly Depressing

In late July I participated in the annual meeting of the National Plant Board (NPB) – the organization representing the states’ phytosanitary agencies. USDA’s APHIS, DHS’ Bureau of Customs and Border Protection (CBP), and various industry associations also participated in the meeting. As usual, I learned lots of depressing developments.

A. Old problems continue to vex:

rhododendron plant infested by P. ramorum; photo by Jennifer Parke, Oregon State University

1) Sudden Oak Death in the Nursery Trade – Again!!!

As you might remember, spring 2019 saw an alarming number of plants infested by the sudden oak death pathogen (Phytophthora ramorum) shipped from west coast nurseries to nurseries in 18 states. Another major incident occurred in 2021. The California Oak Mortality Task Force (COMTF) newsletter for June 2021 reports that one nursery in Oregon shipped plants exposed to P. ramorum to big-box stores in 36 states — twice the number of states that received pathogen-exposed plants in 2019.

The first such incident was in 2004 – 17 years ago! Officials of the states that receive these infested plants are angry that every few years they must divert their resources from other duties to inspect nurseries in their states that have been exposed to the pathogen. They note that these “trace-forward” projects cost state governments money and prevent their carrying out other duties; they also impose significant costs on the in-state nurseries due to holds on sales. When infested plants are found, all these costs rise substantially.

The plant health official from Alabama noted that a single west coast nursery that had repeatedly been found to have infected plants shipped 29 lots of host plants to her state in spring 2021. As is clear from the COMTF article, other states also received thousands of plants that had been exposed to the pathogen. The Alabama official questioned why APHIS tilts so far toward a regulatory system that makes it possible for the “exporting” nurseries to ship. The result – too often – is that an infection at one small business can (repeatedly) impose high costs on hundreds of receiving nurseries and states. [I wonder whether anyone has considered a lawsuit against the source nurseries claiming damages? Would that be successful if the regulatory agencies approved the shipments because – at that time – their inspections had failed to detect the problem?]

Officials from the three west coast states, however, want to support their own nurseries’ efforts to relax regulations and maintain or open markets in the central and eastern states. They point to their own considerable efforts to inspect and certify the pest-free status of nurseries in their states.

Because of the different points of view among the states, the National Plant Board per se has never taken a position on the issue.

However, many states – and even APHIS Deputy Administrator El-Lissy – agree that something is not working. So APHIS is in the midst of reviewing its program, with input from NPB members. Such program reviews have been undertaken several times over the past 18 years. So far, they have never produced a program that effectively stops sales of pathogen-infested plants.

2) Contaminated Wood Packaging

Kevin Harriger of CBP reported that over the nine-month period October 2020 – June 2021, CBP intercepted 1,563 shipments that were in violation of ISPM#15, the international rule that requires that wood packaging be treated to kill pests. Most, or 1,148 shipments (73%), lacked the required mark certifying treatment. Four hundred fifteen (26%) of the total number of shipments had a live pest present. Nearly three quarters of the non-compliant shipments transported miscellaneous cargo. This is not a surprise: all of these characteristics are in keeping with past experience.

Meanwhile, APHIS Deputy Director El-Lissy said APHIS was working with importers, exporting countries’ departments of agriculture, and others to improve compliance. Apparently there were two high-profile incidents when shipments of car components were rejected because of ISPM#15 issues. I am trying to learn more about these incidents.

I recently blogged about the pest risk associated with incoming shipping containers and dunnage.

3) Asian ~~Gypsy~~ Moths (Tussock moths) Still Infesting Ships

Harriger also said that the period 2019-2020 saw the largest number of ships infested by Asian tussock moth eggs since the program began in 2012. [I am aware that the Entomological Society is searching for a new name for this group of insects.] On average, 12 of 100 approaching vessels was infested. CBP is using sophisticated models to identify regions within Asian ports where conditions exacerbate the risk of moth contamination. CBP can match individual ships’ loading records to this information to pinpoint which are most likely to be infested.

Oregon and Washington continue to find both Asian and European tussock moths in traps along the Columbia River. Such detections prompt eradication programs of varying expense and disruption.

[In April, I blogged about a report evaluating the risk posed by several Asian tussock moths; the report was prepared by experts under the auspices of the North American Plant Protection Organization.]

B. In addition to the arrival of new pests, there is an alarming spread of established ones:

1) Beech leaf disease

State phytosanitary officials reported detections of beech leaf disease (BLD) in Maine and Virginia. The devastating impact of BLD on this hard mast tree species is described here. BLD has now spread through much of southern New England (Connecticut, Rhode Island, Massachusetts) and up the coast to Maine. Connecticut reports that trees of all sizes are affected. Maine reports that the disease is widespread in the central coastal region.

beech trees in Prince William Forest Park

Virginia reported that the disease has been detected in Prince William Forest Park, a forested area south of Washington, D.C., managed by the National Park Service. This detection is too recent to say how widespread it is.

2) Laurel wilt

Kentucky’s plant health officer reported that laurel wilt disease has been detected on sassafras trees in Louisville, at the northern tip of the state and across the river from Ohio. He noted that a second host plant, spice bush, is in the nursery trade. While laurel wilt is not regulated, officials are concerned about its impact in natural forests. Neighboring states are concerned.

sassafras in northern Virginia; photo by F.T. Campbell

I learned by looking at the map that laurel wilt has also been detected in Sullivan County, Tennessee, on the Virginia border.

3) Spotted Lanternfly

This pest of grapes, tree fruits, and a wide variety of native trees is spreading in Pennsylvania, Delaware, New Jersey, and Maryland. It has also been found in Ithaca, NY, and in Connecticut. The populations in Virginia and West Virginia also continue to spread; a disjunct outbreak has been detected in Prince William County, VA. (south of D.C.). Most alarming are disjunct populations in Ohio on the West Virginia border and in Indiana on the Ohio River border with northern Kentucky. See map here.

The Indiana population has been present for several years. The affected woodland is close to RV parks and other facilities that make further spread likely.

California has established an external quarantine targetting the spotted lanternfly .

C. Wrestling with Continuing Issues:

1) States try to compensate for APHIS’ end of regulating the emerald ash borer and firewood

The members of the NPB have spent years discussing the pros and cons of continuing to regulate ash wood to contain the emerald ash borer (EAB). As I blogged earlier, APHIS has ended its regulatory program. One state – Minnesota – is seeking to use an APHIS procedure to get APHIS’ continued protection from importation of EAB-infested wood (presumably from Canada). Under the Federally Recognized State Managed Phytosanitary Program (FRSMP), a state petitions APHIS to recognize its program for a specific pest. If APHIS grants that recognition, the agency will support the state by continuing to regulate imports of that pest or commodities that might transport the pest when they are destined for the regulating state.

The states have also tried to formulate a system to maintain regulation of firewood (nearly all states’ firewood regulations were based on the federal regulation of all hardwoods to prevent transport of the EAB). As part of this process, the NPB developed guidelines for adoption of regulations by the individual states (available here). The NPB members are just beginning to explore whether states might set up third-party certification system(s). Among the challenges to any harmonization are states’ differing legal authorities and disagreement on what threat levels should be applied, and for how long.

2) New information about the Asian longhorned beetle in South Carolina

ALB in South Carolina; photo by R. Brad Thompson, APHIS

South Carolina authorities reported that dendrological studies indicated Asian longhorned beetle (ALB) had been present near Charleston, S.C. since 2012, and possibly earlier. The population has the same genetic makeup as the outbreak in Ohio. This might be explained by either transport of infested wood from Clermont County, Ohio, or that wood packaging entering Charleston harbor came from the same part of China. (Charleston is an important port.) In South Carolina, ALB attacks primarily red maple – as is true at the other infestation sites. However, maple densities are much lower in the swamps of South Carolina and scientists don’t know whether the ALB will fly farther or intensify attacks on other host species. Other questions raised by differences between South Carolina and other, more northern, outbreak sites include possible changes in the beetle’s life cycle and flight periods.

Authorities noted the extremely difficult conditions, which impede survey and control efforts – which I described in an earlier blog.

One innovation was sharing of resources: staff from the North Carolina and Tennessee departments of agriculture went to South Carolina to help with surveys. The Resource Sharing Initiative was started a few years ago as a collaborative effort of APHIS and the NPB. This was the first time states tried it. There were several issues that had to be worked out. One issue was the long time it takes to train people to recognize ALB symptoms. All three states’ officials said the project was worthwhile.

black walnut in Fairfax County, VA — in an area where thousand cankers disease has been present for more than a decade; photo by FT Campbell

3) Recinding quarantines of thousand cankers disease of walnut

States which adopted quarantines targetting this insect/pathogen complex a decade ago now think that it poses little risk to black walnut (Juglans nigra) growing in its native range (as distinct from trees planted in the West). Several are in the process of rescinding their quarantines. I think these states have considered the science carefully and are taking the appropriate action.

4) Nursery self-certification – System Set Up; Will Nurseries Participate? Will Customers Support the Process?

Craig Regelbrugge of AmericanHort noted that the SANC program has now been officially launched – it has graduated from being a pilot program. [SANC stands for Systems Approach to Nursery Certification] Participants are exploring incentives to recruit wider participation by nurseries that produce plants and how to get support from plant retailers. SANC is conceived as an elite program for the best nurseries and marketplace leaders. It was never intended to be a remedial program to clean up problem issues such as the P. ramorum debacle. To work, it seems to me, SANC will need to find a way to persuade customers to want to pay more for quality plants. Hence the critical importance of getting retailers involved.

Posted by Faith Campbell

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm

Resistance Breeding – a Useful Strategy

Port-Orford cedar resistance trials at Dorena Center; photo courtesy of Richard Sniezko, USFS

I have written several times about the importance of the United States adopting a comprehensive program to address all aspects of introduced forest pests including breeding of trees resistant to the introduced pests. See Fading Forests III from seven years ago; an earlier blog; and Bonello et al. 2020 (full citation at end of blog), in which we proposed the creation of a federal Center for Forest Pest Control and Prevention to implement end-to-end integrated responses to forest pest invasions. A similar view is being voiced internationally; see, e.g., Buggs et al. 2020.

I have seen efforts to restore pest-decimated tree species to the forest lagging. I complained in a recent blog link that the recent USDA Forest Service report on invasive species (Poland et al. 2021) gave a misleading impression that significant effort was being made on resistance breeding to address several pests.

The USFS does support breeding trees resistant to pests, but in my view this support has been inadequate – including in the USFS report. Others think so, too — see Sniezko and Koch 2017. This insufficiency only grows, despite USDA claims to recognize that promoting resistance to introduced forest pests is an essential component of achieving its strategic goals of maintaining or enhancing productivity while ensuring responsible stewardship of resilient natural resources (Federman and Zankowski 2019).

Work at the Dorena Genetic Research Center

The principal and most notable and successful resistance breeding effort has been the Dorena Genetic Resource Center. The Center was established by, and is funded through the USFS Region 6 Genetic Resource (part of the National Forest System) and Forest Health Management programs. The Center has a solid foundation in the expertise and facilities needed to carry out breeding efforts. Also, it has a 50-plus-year track record.

Dorena has supported breeding of white (five-needle) pines and Port-Orford cedar. Dorena also now provides expertise and some facilities to partners exploring a) breeding Oregon ash to resist the emerald ash borer and b) two Hawaiian trees (koa and ‘ōhi‘a) to resist introduced pathogens (see below). Dorena staff is assisting low-budget, shoe-leather efforts to explore breeding of other trees at risk to non-native pests. These programs are described briefly in Box 8 of Poland et al. 2021. Despite this valuable effort with proven success funding to continue Dorena’s work is tenuous.

White Pine Blister Rust — Efforts to develop resistance to white pine blister rust (WPBR) DMF in five-needle pine species (nine grow across the country) began more than 50 years ago. Currently Dorena focuses on whitebark pine (Pinus albicaulis), denizen of high elevations in the West, along with western white pine (P. monticola), sugar pine (P. lambertiana) , limber pine (P. flexilis), southwestern white pine (P. strobiformis), and foxtail pine (P. balfouriana). Testing whitebark for resistance to WPBR began in 2002. Seedling families from >1,300 parent trees are in various stages of testing. The discovery that some whitebark populations have much higher levels and frequency of partial resistance has allowed rapid distribution of seed. The first restoration plantings in the Pacific Northwest were in 2009.

3-year old seedlings of whitebark pine at Crater Lake National Park; photo by Richard Sniezko, USFS

There are many collaborators – especially the National Park Service, Washington State’s Department of Natural Resources, several Tribes, the Whitebark Pine Ecosystem Foundation, and American Forests. However, planting has been hampered by the high cost of restoration in these high elevation ecosystems, lack of frequent good seed crops on the resistant parent trees, and lack of approval to plant in designated wilderness areas. In the areas with the highest levels of resistant parents, management activities that encourage natural regeneration might be successful. In late 2020 the U.S. Fish and Wildlife Service proposed to list whitebark pine as a Threatened species

Oregon ash (F. latifolia) has not yet been attacked by the emerald ash borer, but all expect EAB to spread to the West coast. Dorena and cooperators have already collected seed from ash trees in Oregon and obtained funding for additional collections, to include Washington and California. The seeds are being stored at both Dorena and the USDA Agriculture Research Service facility at Ft. Collins, Colorado. Seedlings from two dozen families have also been planted at Dorena and a center operated by Washington State University, plus at a USFS Northern Research Station research center in Ohio, where EAB is established and they can be tested for resistance to the insect’s attack.

Koa and ‘ōhi‘a in Hawaii — Regeneration of the koa tree (Acacia koa) has been undercut by the koa wilt pathogen, Fusarium oxysporum f. sp. koae. Dorena initiated efforts with the Hawaii Agricultural Research Center (HARC) to respond in 2003. There has been rapid progress screening seedlings to identify resistant parent trees establishing seed orchards, delineating seed zones, and releasing seed with confirmed levels of resistance for reforestation and restoration (Sniezko and Koch 2017; see also Dudley et al. 2020).

‘ōhi‘a trees killed by rapid ‘ōhi‘a death; photo courtesy of J.R. Friday

When the threat to Hawaii`s most widespread tree ‘ōhi‘a (Metrosideros polymorpha) from rapid ‘ōhi‘a death (ROD) pathogens became apparent, the Dorena staff provided advice on breeding strategies. Its Center Geneticist is part of an ad hoc resistance team. Scientists have identified surviving trees in stands affected by ROD on the Big Island using a variety of methods. These include aerial surveys by drones and fixed-wing aircraft. They then began collecting seeds and cuttings. As of spring 2021, they have collected cuttings or seeds from more than 300 ‘ōhi‘a trees belonging to five varieties. The effort is low-cost, using Americorps volunteers coordinated by a single full-time person, a USFS employee. The program is still in its infancy. It will have to find funding to expand its scope to an operational resistance program once more information on resistance is has been obtained.

Other Efforts

Most other breeding programs are small and poorly funded. In fact, they have been described by one USFS scientist as “hobby projects” of a few scientists determined to try this strategy. Not only are efforts minimal; but also retirement of those few scientists can bring an end to the individual project.

There were greater efforts in the past. I have a document (of unknown origin) from 2011 that describes breeding efforts funded by both the National Forest System and USFS Research and Development. Table 1 listed 16 projects for western conifers; Table 2 listed 32 projects funded by R&D. During this period, the USFS provided start-up funds for the Healthy Forests Initiative, a consortium that sought to prove the concept that genetic engineering could quickly produce an American chestnut able to live and reproduce in its native range. This support was in addition to support for The American Chestnut Foundation backcross hybridization program link.

Part of the problem is the longstanding decline in funding and staffing of USFS research program. A graph in Chapter 6 of FFIII shows the decline in numbers of forest entomologists and pathologists over the 20-year period 1985–2007. Wheeler et al. 2015 discuss the parallel decline in tree breeders and geneticists (citation at end of this blog).

Cuts continue. Funding for research conducted by the USFS Research stations on ten non-native pests decreased from $10 million in Fiscal Year 2010 to just $2.5 million in Fiscal Year 2020 – a cut of more than 70%. I have lobbied for increased appropriations for decades.

The need for new approaches and increased effort is more widely asserted. One example is the group I am working with that promotes a new Center for Forest Pest Control and Prevention. Link A second example is the University of Florida’s recent conference of forest health researchers, representatives of the forest products industry, non-governmental organizations, and leaders of universities with forest-resource programs. This group suggested forming a united organization to increase capacity to improve forest health research. An article outlining the proposal is available here.

The Role of Biotechnology in Breeding Resistant Trees

what happened? same tree a few years apart — a TACF hybrid chestnut

Part of the discussion on forest research explores the proper role of biotechnology in tree species’ restoration. Purdue University hosted a related workshop in April 2021, in which I took part. (“Society and Policy Influences on Biotechnology Risk Assessment for Restoration of Threatened Forest Tree Species”). I hope participants will soon publish a paper based on our discussions.

Meanwhile, Revive & Restore, a wildlife conservation organization promoting the incorporation of biotechnologies into standard conservation practice, sponsored a workshop in June 2020. The 57 conservationists, wildlife biologists, restoration specialists, conservation geneticists, ethicists, and social scientists who participated agreed on an appropriate structure for using biotechnology. These included:

A broader definition of risk and application of new risk assessment tools;
Consideration of the risks of not taking action, as well as going ahead with a proposal;
Transparency about social and cultural values and engaging stakeholders
Monitoring results to ensure actions have been successful, manage uncertainty, and codify lessons learned.

In the literature I read, the workshops I participate in (e.g., National Academy of Sciences 2019; Purdue’s), biotechnology is seen as a potentially helpful set of tools that must be integrated into broader programs, all having research, tree improvement, restoration, and reforestation components. Such programs must have sustained management and resources stemming from public support. (For more complete descriptions of components of a resistance breeding program, see Sniezko and Koch 2017 (full reference below); or Chapter 6 of FFIII). Activities that must be incorporated include:

Germplasm collection and storage (applying the varied strategies that are appropriate);

Research to detect and test potential resistance or tolerance;
Research to identify techniques for producing propagules;
Planting sites that will be secure for decades;
Site preparation & planting;
Post-planting maintenance; and
Monitoring to determine success or problems

During the Purdue workshop, and in my writing, I have emphasized the principal hindrance to progress is the lack of resources being allocated to resistance breeding. USFS and academic scientists determined to pursue breeding approach must scrounge for funds. I describe some of their efforts below.

Collaborations on Breeding for Specific Species

(still) healthy hemlocks in Cook Forest State Park, Pennsylania; photo by F.T. Campbell

USFS Hemlock Woolly Adelgid (HWA) Initiative [apparently no website]

This initiative was developed under the leadership and direction of FHP staff. The list of cooperators includes dozens of state, federal, university and private organizations. The annual budget has averaged between $2.5 and $3.5 million. Most resources are apparently allocated to biocontrol, but some funding has been provided for breeding activities, including:

Seed collection and storage for both Carolina and eastern hemlocks. Two seed orchards have been established in western North Carolina. I believe they are protected from the hemlock woolly adelgid (HWA) by application of pesticides.
Research on these tree species’ silviculture and ecology, including manipulation of sunlight levels to protect seedlings from the adelgid and promote growth

The 2021-2025 Program – currently under review – foresees more integrated pest management applying biocontrol, chemical control, and silviculture. It aims to maintain the health of hemlocks being used in breeding programs and “explore” hemlock replacement options, such as hybrids or HWA-tolerant hemlocks (Mayfield et al. 2021). This effort is encouraging, but I have heard complaints from academics that they can’t get funding to pursue what they regard as promising breeding strategies.

Other small programs to breed resistant hemlocks are under way. The Forest Restoration Alliance (formerly the Alliance to Save Threatened Forests) asks citizens to identify surviving hemlocks and balsam firs. The Alliance has collected and propagated both cuttings and seeds and is testing their resistance.

Ash and Other Trees of the Upper Midwest

To date, few resources have been allocated to resistance breeding of ash. Between 2003 and 2017, only about 7% of research funds allocated to ash and emerald ash borer DMF have been devoted to host resistance. Of the host resistance research, 61% applied to identifying mechanisms, 14% to use of transgenics to develop resistance, only 7% (0.5% of the total research) has supported actual breeding for resistance (Sniezko and Koch 2017).

In May 2021 the USFS announced it was seeking funds from the water-focused Great Lakes Restoration Initiative. The USFS expects to receive up to $5.4 million for reforestation, ecosystem restoration. and forest health improvements on non-federal lands in the Great Lakes basin. (This includes parts of the states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania and Wisconsin). The announcement doesn’t mention resistance breeding for ash, beech, hemlock, or other trees in the region. I hope some of the new funds will be allocated to this strategy.

“lingering” ash; photos courtesy of Jennifer Koch, USFS

In an encouraging show of entrepreneurship, USFS scientists and others have formed the Great Lakes Basin Forest Health Collaborative – a partnership with Holden Forests and Gardens, American Forests, and USFS (Kappler et al. 2021). The purpose of the Collaborative is to advance resistance breeding for these important tree species. The initial focus is on the five ash species in the region, especially black ash (Fraxinus nigra) link to blog The Collaborative is recruiting a network of partners, and will provide training and technology transfer. The partners will provide volunteers and other resources. Partners do not have to be within the region if their work helps the Great Lakes Basin, but plantings have to be there.

Partners will help identify survivor trees with potential resistance (e.g., “lingering” ash); establish clone banks and/or seed orchards; and manage seed collections. Each partner will operate independently, but in collaboration with the others. The initial focus is on obtaining representative seed collections of ash and hemlock. Then cloning, testing resistance, and crosses can begin. Eventually select lines will be chosen for bulking up and reintroduction.

In future the Collaboration hopes to engage in breeding hemlocks and identifying beech trees that remain healthy in areas heavily impacted by beech leaf disease (BLD).

Other efforts under way include the Monitoring and Managing Ash (MaMA) Program, based in the Ecological Research Institute in New York State.

Beech trees with resistance to beech bark disease (BBD) were identified as early as the 1980s, but a breeding program was begun only in 2002. A collaborative, multi-agency effort has resulted in the establishment of five regional American beech seed orchards with four others in progress as of 2017. Partners provide a cost-effective process for identifying resistant parent trees. State and National Forest personnel surveyed natural forests for candidate trees and then tested each tree and identified markers associated with resistance (Sniezko and Koch 2017).

Challenges Beyond Breeding

Large-scale restoration of tree species across much of their ranges will require significant inputs of funds, over long time periods, as well as resolving daunting logistical issues.

Some think the most likely scenario will be to plant focal areas, or islands, that can aid future natural regeneration (Sniezko and Koch 2017). The American Chestnut Foundation (TACF) anticipates it will take 1,000 years to re-establish American chestnut DMF across its range through a process of three phases: long-term research and demonstration plantings; a relatively small-scale public horticultural program using trees and/or pollen made available by TACF; and a larger-scale public restoration program using progeny from years of outcrossing and production. (This assumes APHIS approves release of the transgenic “Darling 58” tree, plus – I believe – progress in developing resistance to root disease caused by Phytophthora cinnamomi). Already good progress using focal areas has started with several white pine species, and a national plan is in the works for whitebark pine.

Such efforts will require access to land that can be protected from other uses, e.g., development for decades or centuries. Also it will require management of sites to protect propagules from browsing wildlife (deer, rabbits!), provide adequate water and light, and probably give plantings a competitive advantage in relation to other plants growing there …

non-resistant elms will grow anywhere! photo by F.T. Campbell

And there is the issue of how a relatively small number of resistant propagules will succeed in spreading their improved genetics in areas where non-improved elm, ash, beech and hemlock are reproducing naturally. Is reproduction of unimproved trees likely to continue in the face of new and old pests’ spread? If biocontrol agents succeed in reducing a pest’s impact on a host tree species, will that enhance the competitive ability of unimproved trees to the disadvantage of genetically improved conspecifics? What are realistic expectation for programs, and for their success?

Criteria for Success

Woodcock, Marzano, and Quine (2019) analyzed five breeding programs to identify aspects that contribute to success. Four of the programs were in North America; they targetted chestnut, western white pines, and Sitka spruce & white pine weevil. They concluded that

Success is influenced by the level of resistance present in individual trees, the frequency of resistance in the population, and the heritability of resistance.
It is important to consider current and potential future risks to the species in addition to the target pest or pathogen— the benefits of trees resistant to a specific threat are negated if it is susceptible to other threats.
Demand [for a resistant tree to plant] should be evaluated, and the priorities of potential supporters and end users should inform the methods used to produce resistant trees.
Operational deployment should balance the urgency of the threat with the consequences if resistant material does not perform as hoped. Urgency might differ for an emerging pest or pathogen.
Deployment strategies should be informed by the risks of imposing a strong selection pressure on the pest or pathogen to evolve to overcome host resistance, and by potential impacts on partially resistant trees.
Continued monitoring of field performance is important for evaluation, and can help to identify and mitigate emerging threats (e.g. new pathogen strains).

SOURCES

Bonello, P., F.T. Campbell, D. Cipollini, A.O. Conrad, C. Farinas, K.J.K. Gandhi, F.P. Hain, D. Parry, D.N. Showalter, C. Villari, and K.F. Wallin. 2020. Invasive tree pests devastate ecosystems – A proposed new response framework. Frontiers in Forests and Global Change. January 2020. Volume 3, Article 2

Buggs, R.J.A. 2020 Changing perceptions of tree resistance research. Plants, People, Planet. 2020; 2: 2– 4. https://doi.org/10.1002/ppp3.10089

Dudley, N.; Jones, T.; Gerber, K.; Ross-Davis, A.L.; Sniezko, R.A.; Cannon, P.; Dobbs, J. 2020. Establishment of a Genetically Diverse, Disease-Resistant Acacia koa A. Gray Seed Orchard in Kokee, Kauai: Early Growth, Form, and Survival. Forests 2020, 11, 1276

Federman, S. and P. Zankowski. 2019. Strategic science planning for responsible stewardship and plant protection at the U.S. Department of Agriculture. Plants, People, Planet © New Phytologist Trust 2019;00:1–4. https://doi.org/10.1002/ ppp3.10075

Kappler, R., C. Blashka, D. burke, E. Hall, C. Pike, J. Koch. 2021. Great Lakes Basin Forest Health Collaborative: What it’s all about. North American Forest Insect Work Conference 28 May 2021

Mayfield, A.E. III, Salom, S., Jetton, R., Havill, N., Rhea, R., and Mausel, D. 2021. North American Forest Insect Work Conference 28 May 2021. Spread, impact and management of HWA in eastern North America

National Academies of Sciences, Engineering, and Medicine. 2019. Forest Health and Biotechnology: Possibilities and Considerations. Washington, DC: The National Academies Press. https://doi.org/10.17226/25221.

Poland, T.M., P. Patel-Weynand, D.M Finch, C.F. Miniat, D.C. Hayes, V.M Lopez, editors. 2021. Invasive Species in Forests and Rangelands of the United States. A Comprehensive Science Synthesis for the US Forest Sector. Springer

Sniezko, R.A. and J. Koch. 2017. Breeding trees resistant to insects & diseases: putting theory into application. Biol Invasions. 2017. 19:3377-3400. DOI 10.1007/s10530-017-1482-5

Wheeler, N.C., K.C. Steiner, S.E. Schlarbaum, D.B. Neale. 2015. The Evolution of Forest Genetics and Tree Improvement Research in the United States, Journal of Forestry, Volume 113, Issue 5, September 2015, Pages 500–510, https://doi.org/10.5849/jof.14-120

Woodcock, P., M. Marzano, C.P. Quine. 2019. Key lessons from resistant tree breeding programmes in the Northern Hemisphere. Annals of Forest Science (2019)76:51 https://doi.org/10.1007/s13595-019-0826-y

Posted by Faith Campbell

On the Rise: US Imports & the Risks of Tree-killing Pests

containers at Port of Long Beach; photo courtesy of Bob Kanter, Port of Long Beach

Here I update information on two of the major pathways by which tree-killing pests enter the United States: wood packaging and living plants (plant for planting).

Wood Packaging

Looking at wood packaging material, we find rising volumes for both shipping containers – and their accompanying crates and pallets; and dunnage.

Crates and pallets – Angell (2021; full citation at the end of the blog) provides data on North American maritime imports in 2020. The total number of TEUs [a standardized measure for containerized shipment; defined as the equivalent of a 20-foot long container] entering North America was 30,778,446.U.S. ports received 79.6% of these incoming containers, or 24,510,990 TEUs. Four Canadian ports handled 11.4% of the total volume (3,517,464 TEUs; four Mexican ports 8.9% (2,749, 992 TEU). Angell provides data for each of the top 25 ports, including those in Canada and Mexico.

To evaluate the pest risk associated with the containerized cargo, I rely on a pair of two decade-old studies. Haack et al. (2014) determined that approximately 0.1% (one out of a thousand) shipments with wood packaging probably harbor a tree-killing pest. Meissner et al. (2009) found that about 75% of maritime shipments contain wood packaging. Applying these calculations, we estimate that 21,000 of the containers arriving at U.S. and Canadian ports in 2020 might have harbored tree-killing pests.

While the opportunity for pests to arrive is obviously greatest at the ports receiving the highest volumes of containers with wood packaging, the ranking (below) does not tell the full story. The type of import is significant. For example, while Houston ranks sixth for containerized imports, it ranks first for imports of break-bulk (non-containerized) cargo that is often braced by wooden dunnage (see below). Consequently, Houston poses a higher risk than its ranking by containerized shipment might indicate.

Also, Halifax Nova Scotia ranks 22^nd for the number of incoming containerized shipments (258,185 containers arriving). However, three tree-killing pests are known to have been introduced there: beech bark disease (in the 1890s), brown spruce longhorned beetle (in the 1990s), and European leaf-mining weevil (before 2012) [Sweeney, Annapolis 2018]

The top ten ports receiving containerized cargo in 2020 were

Port 2020 market share 2020 TEU volume

Los Angeles 15.6% 4,652,549

Long Beach 13% 3,986,991

New York/New Jersey 12.8% 3,925,469

Savannah 7.5% 2,294,392

Vancouver BC 5.8% 1,797,582

Houston 4.2% 1,288,128

Manzanillo, MX 4.1% 1,275,409

Seattle/Tacoma 4.1% 1,266,839

Virginia ports 4.1% 1,246,609

Charleston 3.3% 1,024,059

Import volumes continue to increase since these imports were recorded. U.S. imports rose substantially in the first half of 2021, especially from Asia. Imports from that content reached 9,523,959 TEUs, up 24.5% from the 7,649,095 TEUs imported in the first half of 2019. The number of containers imported in June was the highest number ever (Mongelluzzo July 12, 2021).

Applying the calculations from Haack et al. (2014) and Meissner et al. (2009) to the 2021 import data, we find that approximately 7,100 containers from Asia probably harbored tree-killing pests in the first six months of the year. (The article unfortunately reports data only for Asia.) Industry representatives quoted by Mongelluzzo expect high import volumes to continue through the summer. This figure also does not consider shipments from other source regions.

Dunnage on the pier at Port of Houston; photo by Port of Houston

Infested dunnage – Looking at dunnage, imports of break-bulk (non-containerized) cargo to Houston – the U.S. port which receives the most – are also on the upswing. Imports in April were up 21% above the pandemic-repressed 2020 levels.

Importers at the port complain that too often the wooden dunnage is infested by pests, despite having been stamped as in compliance with ISPM#15. CBP spokesman John Sagle confirms that CBP inspectors at Houston and other ports are finding higher numbers of infested shipments. CBP does not release those data, so we cannot provide exact numbers (Nodar, July 19, 2021).

The Houston importers’ suspicion has been confirmed by data previously provided by CBP to the Continental Dialogue on Non-Native Insects and Diseases. From Fiscal Year 2010 through Fiscal Year 2015, on average 97% of the wood packaging (all types) found to be infested bore the stamp. CBP no longer provides data that touch on this issue.

Detection of pests in the dunnage leads to severe problems. Importers can face fines up to the full value of the associated cargo. Often, the cargo is re-exported, causing disruption of supply chains and additional financial losses (Nodar, July 19, 2021).

In 2019 importers and shippers from the Houston area formed an informal coalition with the Cary Institute of Ecosystem Studies to try to find a solution to this problem. The chosen approach is for company employees to be trained in CBP’s inspection techniques, then apply those methods at the source of shipments to identify – and reject – suspect dunnage before the shipment is loaded. In addition, the coalition hopes that international inspection companies, which already inspect cargo for other reasons at the loading port will also be trained to inspect for pests. Steps to set up such a training program were interrupted by the COVID-19 pandemic, but are expected to resume soon (Nodar, July 19, 2021).

Meanwhile, the persistence of pests in “treated” wood demands answers to the question of “why”. Is the cause fraud – deliberate misrepresentations that the wood has been treated when it has not? Or is the cause a failure of the treatments – either because they were applied incorrectly or they are inadequate per se?

ISPM#15 is not working adequately. I have said so. Gary Lovett of the Cary Institute has said so (Nodar July 19, 2021). Neither importers nor regulators can rely on the mark to separate pest-free wood packaging from packaging that is infested.

APHIS is the agency responsible for determining U.S. phytosanitary policies. APHIS has so far not accepted its responsibility for determining the cause of this continuing issue and acting to resolve it. Preferably, such detection efforts should be carried out in cooperation with other countries and such international entities as the International Plant Protection Convention (IPPC) and International Union of Forest Research Organizations (IUFRO). However, APHIS should undertake such studies alone, if necessary.

In the meantime, APHIS and CBP should assist importers who are trying to comply by facilitating access to information about which suppliers often supply wood packaging infested by pests. The marks on the wood packaging includes a code identifying the facility that carried out the treatment, so this information is readily available to U.S. authorities.

Plants for Planting

A second major pathway of pest introduction is imports of plants for planting. Data on this pathway are too poor to assess the risk – although a decade ago it was found that the percentage of incoming shipments of plants infested by a pest was 12% – more than ten times higher than the proportion for wood packaging (Liebhold et al. 2012).

According to APHIS’ annual report, in 2020 APHIS and its foreign collaborators inspected 1.05 billion plants in the 23 countries where APHIS has a pre-clearance program. In other words, these plants were inspected before they were shipped to the U.S. At U.S. borders, APHIS inspected and cleared another 1.8 billion “plant units” (cuttings, rooted plants, tissue culture, etc.) and nearly 723,000 kilograms of seeds. Obviously, the various plant types carry very different risks of pest introduction, so lumping them together obscures the pathway’s risk. The report does not indicate whether the total volume of plant imports rose or fell in 2020 compared to earlier years.

SOURCES

Angell, M. 2021. JOC Rankings: Largest North American ports gained marke share in 2020. June 18, 2021. https://www.joc.com/port-news/us-ports/joc-rankings-largest-north-american-ports-gained-market-share-2020_20210618.html?utm_campaign=CL_JOC%20Port%206%2F23%2F21%20%20_PC00000_e-production_E-103506_TF_0623_0900&utm_medium=email&utm_source=Eloqua

Haack R.A., Britton K.O., Brockerhoff, E.G., Cavey, J.F., Garrett, L.J., et al. (2014) Effectiveness of the International Phytosanitary Standard ISPM No. 15 on Reducing Wood Borer Infestation Rates in Wood Packaging Material Entering the United States. PLoS ONE 9(5): e96611. doi:10.1371/journal.pone.0096611

Liebhold, A.M., E.G. Brockerhoff, L.J. Garrett, J.L. Parke, and K.O. Britton. 2012. Live Plant Imports: the Major Pathway for Forest Insect and Pathogen Invasions of the US. www.frontiersinecology.org

Meissner, H., A. Lemay, C. Bertone, K. Schwartzburg, L. Ferguson, L. Newton. 2009. Evaluation of Pathways for Exotic Plant Pest Movement into and within the Greater Caribbean Region. A slightly different version of this report is posted at 45^th Annual Meeting of the Caribbean Food Crops Society https://econpapers.repec.org/paper/agscfcs09/256354.htm

Mogelluzzo, B. July 12, 2021. Strong US imports from Asia in June point to a larger summer surge.

Nodar, J. July 19, 2021. https:www.joc.com/breakbulk/project-cargo/breakbult-volume-recovery-triggers-cbp-invasive-pest-violations_20210719.htm

Posted by Faith Campbell

USFS report: treatment of introduced forest pests

still-healthy hemlocks in Cook Forest State Park, PA; photo by F.T. Campbell

In a separate blog, I evaluated several aspects of the report as they apply to invasive species generally. Here I focus on invasive insects and pathogens that attack North American tree species (that is, forest pests).

As I said in the separate blog, I doubt that the book will stimulate policy-makers to increase Forest Service resources allocated to invasive species research, much less management. Sections 14.5 and 16.5 of the report state that the continued absence of a comprehensive investigation of the impacts of invasive species, especially the full value of ecosystem services lost, is a barrier to policymakers seeking to develop priorities and realistic management strategies.

I think the book’s editors tried to provide as much information about impacts as possible given existing knowledge. But the book’s length, comprehensive inclusion of all bioinvaders, organizational structure, and the detailed discussions of theories and models reduce the contribution the book might make to management decisions. I did not find “lessons learned” that could be applied in the policy realm.

Chapters address impacts in terrestrial and aquatic systems; impacts on ecosystem processes; impacts on various sectors of the economy and cultural resources; interactions with climate change and other disturbances; management strategies for species and landscapes; tools for inventory and management. Each chapter evaluates the current status of knowledge about the topic and suggests research needs. There are also summaries of the invasive species situation in eight regions.

The choice to organize the book around the chapters listed above means that some information one might expect to find in a book about invasive species is scattered or even absent. This is not a good resource for concise descriptions of individual invasive species and their impacts. That information is scattered among the chapters depending on whether some aspect of the species was chosen to illustrate a scientific challenge or success. The regional summaries partially remedy this problem – but they do not provide perspective on organisms that have invaded more than one region, e.g., emerald ash borer or white pine blister rust. To some extent, information about individual species is provided in the several subchapters on forest insects and pathogens. Or the reader of the PDF version can use the word search function!

Of course, information on several individual high-profile bioinvaders can be found in other publications; see the species write-ups and references posted at www.dontmovefirewood.org. Under these circumstances, a description of invasive species impacts from the ecosystem perspective is a welcome addition. I have long wished for a “crown to root zone” description of invasive species’ impacts.

HWA-killed hemlocks in Linville Gorge, NC; photo by Steven Norman, USFS

In this blog, I will focus on issues that the report raises that I found most interesting.

Information in the Report on Invasive Insects & Pathogens that Attack North American Trees

At several places the report states that non-native pests that have the potential to threaten the survival of an entire tree genus should be a high priority (p. 136) (what actions should be prioritized are not specified). They name the emerald ash borer (EAB) and Dutch elm disease. Elsewhere, EAB and hemlock woolly adelgid (HWA) are described as among the most significant threats to forests in the Eastern U.S. While EAB and HWA have certainly received considerable attention from the Forest Service, threats to elm have not. (I regret that the timing of the report precluded reference to Kevin Potter’s priority-setting publication. Potter is not listed as a co-author of the book.)

Hemlock woolly adelgid, emerald ash borer, chestnut blight, white pine blister rust (WPBR), and laurel wilt are cited as examples of highly virulent, host-specific agents that kill dominant, abundant, and ecologically unique hosts (p.18), resulting in exceptionally severe long-term impacts. WPBR and HWA specifically can have profound and far-reaching negative effects on ecosystem structure and function. These can rise to the level of an irreversible change of ecological state (p. 97). Of this list, no federal agency has allocated many resources to efforts to slow the spread of laurel wilt. The Forest Service is certainly tracking its spread and impacts.

Exaggerations or Errors

I think the report exaggerates the level of resources allocated to host resistance breeding. The report mentions programs targetting Dutch elm disease, beech bark disease, EAB, HWA and laurel wilt. It describes programs for white pines and Port-Orford cedar as examples of success. However, I would say that all the programs, except American chestnut, are starved for funds and other resources. The report’s authors concede this on p. 195.

TACF American chestnut in field trial; photo by F.T. Campbell

I think the report is too optimistic about the efficacy – so far – of biocontrol agents targeting HWA & EAB. On the other hand, I appreciate the report’s recognition that application of augmentative biocontrol of the Sirex woodwasp is more complicated in North America than in Southern Hemisphere countries (p. 162).

I am concerned about the statement that many plant pathogens are transported, but few have major impact. Examples in the U.S. are said to be WPBR, chestnut blight, and Phytophthora ramorum (p. 97). However, the report does not mention laurel wilt – which has a broad host range; nor rapid ‘ōhi‘a death — which threatens the most widespread tree species on the Hawaiian Islands. Nor does it mention several pathogens attacking single tree species, including beech bark disease, Port-Orford cedar root disease, and butternut canker. The report was written before recognition of beech leaf disease. The report notes that the three diseases it did mention have huge impacts. I am greatly disappointed that the report does not address how scientists and managers should deal with this “black swan” problem other than long discussions of data gaps, and ways to improve models of introduction and spread.

In addition, I am concerned that the discussion of economic factors that influence trade flows and accompanying invasive species (p. 308) focusses too narrowly on inspection alone, rather than other strategies for curtailing introduction. This section also shortens a description of the point made in Lovett et al. (2016). The report notes that Lovett et al. (2016) say that rates of introduction of wood-boring species decreased after ISPM#15 was implemented. However, the report leaves out the major caveat in that paper and the studies by Haack et al. (2014) and Leung et al. (2014) on which it is based: the reduction was insufficient to protect America from damaging introductions! [A further error has crept in: the Haack study explicitly excluded imports from China from their calculations. The Lovett paraphrase is not really clear on this matter.]

Curiosities/Concerns Re: Regional Write-Ups

I wish the sections on the Northwest and Southwest region discussed why areas with so many characteristics favoring introduction of plant pests – major ports, extensive transportation networks, major horticultural industry, extensive agriculture, and abundant urban and native forests – have so few damaging forest pests. (Admittedly, those present are highly damaging: white pine blister rust, sudden oak death, Port-Orford cedar root disease, pitch canker, balsam woolly adelgid, larch casebearer, polyphagous shot hole borer (I add Kuroshio shot hole borer), and banded elm bark beetle). The report does mention the constant threat of introduction of the European and Asian gypsy moths. (The Entomological Society of America has decided to coin a new common name for these insects; they currently to be called by the Latin binomial Lymatria dispar). The report notes that 22 species of non-native bark and ambrosia beetles have recently been introduced in the Southwest.

The report cites a decade-old estimate by Aukema et al. (2010) in saying that a small proportion of introduced pest species has killed millions of trees or pushed ecologically foundational species toward functional extinction. The figure was 14% of the more than 450 non-native forest insect species. I greatly regret that overlapping preparation and publication periods precluded inclusion of data from studies by Potter, Guo, and Fei. http://nivemnic.us/what-fia-data-tell-us-about-non-native-pests-of-americas-forests/

Section 7.3 of the report discusses frameworks for setting priorities. It identifies five factors: 1) pest species having the greatest negative impacts; 2) uniqueness of the affected ecosystem or community; 3) state of the invasion in space and time; 4) management goals; 5) availability of effective tools. Examples of species meeting these criteria include EAB and Dutch elm disease (pest threatens entire host genus); white pine blister rust on whitebark pine (key species in a system with low arboreal diversity).

The report notes increasing understanding of critical aspects of several important pests’ biology and host interactions – but it does not sufficiently acknowledge the decades of effort required to achieve this knowledge. The time required for additional scientific advances will probably be equal or greater, given falling number of “ologists” in government and academia.

I appreciate inclusion of a discussion (Sections 8.3.1 and 8.3.2) on breeding trees resistant to introduced pests

dead Port-Orford cedar in Redwoods National Park; photo by Richard Sniezko, USFS

This section states that host resistance, forest genetics, and tree improvement might be the most effective approaches to managing many established pests. The section says such breeding does not require the use of genetically modified organisms, although transgenic or gene editing technologies can provide useful tools. I appreciate the report conceding that necessary infrastructure and expertise has been declining for two decades (p. 195).

In discussing international cooperation to reduce transport of invasive species, the report refers to increasing availability of data allowing identification of potentially damaging species in their regions of origin. Again, since this chapter was written, the Forest Service has increased its engagement on this approach: the USFS International Program is supporting sentinel plantings managed by the International Plant Sentinel Network (http://www.plantsentinel.org) … see my recent blog here.

SOURCE

Posted by Faith Campbell

USFS invasive species report: Herculean effort that could have had greater impact

In February the USFS published a lengthy analysis of invasive species: Invasive Species in Forests and Rangelands of the United States. A Comprehensive Science Synthesis for the US Forest Sector (Poland et al. 2021; full citation at the end of the blog). More than 100 people contributed to the book; I helped write the chapters on legislation and regulations and international cooperation. The book is available for download at no cost here.

Miconia – one of many invasive plants damaging ecosystems in Hawai`i

I greatly appreciate the effort. Authors first met in 2015, and most chapters were essentially written in 2016. The long delay in its appearance came largely from negotiations with the publisher. The delay means some of the information is out of date. I am particularly aware that several experts – e.g., Potter, Guo, and Fei – have published about forest pests since the Aukema source cited. I wonder whether inclusion of their findings might change some of the conclusions about the proportion of introduced pests that cause noticeable impacts.

Since the report’s publication in February I have struggled with how to describe and evaluate this book. What is its purpose? Who is its audience? The Executive Summary says the report is a sector-wide scientific assessment of the current state of invasive species science and research in the U.S.

However, the Introduction states a somewhat different purpose. It says the report documents invasive species impacts that affect ecosystem processes and a wide range of economic sectors. This would imply an intention to enhance efforts to counter such effects– not just to shape research but also to change management. Indeed, the Conclusion of the Executive Summary (pp. xvi-xvii) is titled “An Imperative for Action”.

I am not the author to evaluate how effectively the book sets out research agendas. Regarding its usefulness in prompting policy-makers to do more, I regretfully conclude that it falls short.

Getting the balance right between an issue’s status and what needs to be done is difficult, perhaps impossible. I appreciate that the report makes clear how complex bioinvasion and ecosystem management and restoration are. Its length and density highlight the difficulty of making progress. This daunting complexity might well discourage agency leadership from prioritizing invasive species management.

On the other hand, summary sections sometimes oversimplify or bury important subtleties and caveats. The question of whether some key questions can ever be resolved by science is hinted at – but in detailed sections that few will read. The same is true regarding the restrictions imposed by funding shortfalls.

The Report Would Have Benefitted from Another Round of Editing

Editing this tome was a Herculean task. I feel like a curmudgeon suggesting that the editors do more! Nevertheless, I think the report would have been improved by the effort. One more round of editing – perhaps involving a wider range of authors – could have pulled together the most vital points to make them more accessible to policymakers. It could also have tightened the ecosystem-based descriptions of impacts, which are currently overwhelmed by too much information.

A precis for policymakers

A precis focused on information pertinent to policymakers (which the current Executive Summary does not) should contain the statement that the continued absence of a comprehensive investigation of invasive species’ impacts hampers research, management, and policy (mentioned only in §16.5, on p. 332). It should note situations in which insufficient funding is blocking recommended action. I note three examples: programs aimed at breeding trees resistant to non-native pests (resource issues discussed only in §§8.3.1 and 8.3.2, p. 195); sustaining “rapid response” programs (§6.4.3, p. 125); costs of ecosystem restoration, especially for landscape-level restoration (§16.4). I am sure there are additional under-funded activities that should be included!

cross-bred ash seedlings being tested for vulnerability to EAB; photo courtesy of Jennifer Koch

Other important information that should be highlighted in such a precis includes the statement that many ecosystems have already reached a point where healthy functions are in a more tenuous balance due to invasive species (p. 51). Effective carbon storage and maintaining sustainable nutrient and water balance are at risk. Second, costs and losses caused by invasive forest pests generally fall disproportionately on a few economic sectors and households. They cannot be equated to governmental expenditures alone (p. 305). Third, even a brief estimate of overall numbers of invasive species appears only in §7.4. Information about individual species is scattered because it is used as example of particular topic (e.g., impacts on forest or grassland ecosystems, or on ecosystem services, or on cultural values).

Ecosystem Impacts Overwhelmed

As noted above, the report laments the absence of a comprehensive investigation of invasive species’ impacts. Perhaps the editors intended this report to partially fill this gap. To be fair, I have long wished for a “crown to root zone” description of invasive species’ impacts at a site or in a biome. Concise descriptions of individual invasive species and their impacts are not provided by this report, but they can be found elsewhere. (The regional summaries partially address the problem of too much information – but they do not provide perspective on organisms that have invaded more than one region, e.g., emerald ash borer or white pine blister rust.) Another round of editing might have resulted in a more focused presentation that would be more easily applied by policymakers.

Welcome Straightforward Discussion of Conceptual Difficulties

I applaud the report’s openness about some important overarching concepts that science cannot yet formulate. If supportable theories could be conceived, they would assist in the development of policies:

Despite decades of effort, scientists have not established a clear paradigm to explain an ecosystem’s susceptibility to invasion (p. 85). Invasibility is complex: it results from a dynamic interplay between ecosystem condition and ecological properties of the potential invader, especially local propagule pressure.
Scientists cannot predict how climate warming will change distributions of invasive species [see Chapter 4] and alter pathways. This inability hampers efforts to develop effective prevention, control, and restoration strategies (p. xi). Climate change and invasive species need to be studied together as interactive drivers of global environmental change with evolutionary consequences.

The Report’s Recommendations

Policy-oriented recommendations are scattered throughout the report. I note here some I find particularly important:

Measures of progress should be based on the degree to which people, cultures, and natural resources are protected from the harmful effects of invasive species.
Managers should assess the efficacy of all prevention, control, and management activities and their effect upon the environment. Such an evaluation should be based on a clear statement of the goals of the policy or action. [I wish the report explicitly recognized that both setting goals and measuring efficacy are difficult when contemplating action against a new invader that is new to science or when the impacts are poorly understood. Early detection / rapid response efforts are already undermined by an insistence on gathering information on possible impacts before acting; that delay can doom prospects for success.]
- Risk assessment should both better incorporate uncertainty and evaluate the interactions among multiple taxa. Risk assessment tools should be used to evaluate and prioritize management efforts and strategies beyond prevention and early detection/rapid response.
- Economic analyses aimed at exploring tradeoffs need better tools for measuring returns on invasive species management investments (§16.5).
Actions that might be understood as “restoration” aim at a range of goals along the gradient between being restored to a known historic state and being rehabilitated to a defined desired state. The report stresses building ecosystem resilience to create resistance to future invasions, but I am skeptical that this will work re: forest insects and disease pathogens.
Propagule pressure is a key determinant of invasion success. Devising methods to reduce propagule pressure is the most promising to approach to prevent future invasions (p. 115). This includes investing in quarantine capacity building in other countries can contribute significantly to preventing new invasions to the US.
Resource managers need additional studies of how invasive species spread through domestic trade, and how policies may differ between foreign and domestic sources of risk.

I appreciate the report’s attention to such often-ignored aspects as non-native earthworms and soil chemistry. I also praise the report’s emphasis on social aspects of bioinvasion and the essential role of engaging the public. However, I think the authors could have made greater use of surveys conducted by the Wisconsin Department of Natural Resources and The Nature Conservancy’s Don’t Move Firewood program.

Lost Opportunities

I am glad that the report makes reference to the “rule of 25” rather than “rule of 10s”. I would have appreciated a discussion of this topic, which is a current issue in bioinvasion theory. As noted at the beginning of this blog, the long time between when the report was written and when it was published might have hampered such a discussion

Also, I wish the report had explored how scientists and managers should deal with the “black swan” problem of infrequent introductions that have extremely high impacts. The report addresses this issue only through long discussions of data gaps, and ways to improve models of introduction and spread.

I wish the section on the Northwest Region included a discussion of why an area with so many characteristics favoring bioinvasion has so few damaging forest pests. Admittedly, those present are highly damaging: white pine blister rust, sudden oak death, Port-Orford cedar root disease, balsam woolly adelgid, and larch casebearer. The report also notes the constant threat that Asian and European gypsy moths will be introduced. (The Entomological Society of America has decided to coin a new common name for these insects; they currently to be called by the Latin binomial Lymatria dispar).

And I wish the section on the Southeast and Caribbean discussed introduced forest pests on the Caribbean islands. I suspect this reflects a dearth of research effort rather than the biological situation. I indulge my disagreement with the conclusion that introduced tree species have “enriched” the islands’ flora.

SOURCE

Poland, T.M., P. Patel-Weynand, D.M Finch, C.F. Miniat, D.C. Hayes, V.M Lopez, editors. 2021. Invasive species in Forests and Rangelands of the United States. A Comprehensive Science Synthesis for the US Forest Sector. Springer

Posted by Faith Campbell

“Rule of Tens” – Time to Refine It

are wood-borers examples of species more likely to “proceed through the steps of invasion” than the theory suggests?

Much of the literature about biological invasion has relied on the “tens rule”. First enunciated in the mid-1990s by Williamson and Fitter (1996), it was actually conceived a decade earlier by Williamson and Brown (1986).

The “tens rule” hypothesizes that about 10% of all species transported to a new environment will be released or escape and become introduced species. Subsequently, 10% of those introduced species establish viable populations in the wild. Finally, about 10% of the established species become highly damaging. That is, 1% of the number originally transported to the new environment is a highly damaging invader.

Is the “tens rule” supported by evidence?

Empirical support for the hypothesis has been mixed; the number of studies questioning it has increased over the decades (Jeschke and Pyšek 2018). So Jeschke and Pyšek (2018) decided to evaluate the basis for the hypothesis. First, they divided the hypothesis into two sub-hypotheses so they could separate the concept of impact from the process of introduction, establishment, and spread. They justified this separation by noting that novel species can have an impact at any stage. The two sub-hypotheses:

1^st sub-hypothesis: At each of the three transitions between the invasion stages listed here the number of species completing the transition is reduced by 90% (invasion tens rule).

transport to exotic range

transition

introduction (release or escape into the environment)

transition

establishment of a least one self-sustaining population

transition

spread

2^nd sub-hypothesis: about 10% of established non-indigenous species cause a significant detrimental impact. This sub-hypothesis applies to the transition from establishment (iii, above) to significant impact (iv). Stepping back to the earlier introduction, so as to consider the situation overall, about 1% of all introduced non-native species cause a significant detrimental impact; this sub-hypothesis thus relates to the transition from introduction (ii) to significant impact (iv).

Jeschke and Pyšek carried out a quantitative meta-analysis of 102 empirical tests of the tens rule drawn from 65 publications. They found no support for the “invasion tens rule”. Indeed, their analysis found that about 24% of non-native plant and 23% of non-native invertebrate species are successful in taking consecutive steps of the invasion process. Among non-native vertebrates, about 51% are successful in taking consecutive steps of the invasion process.

The “impact tens rule” is also not supported by currently available evidence. However, Jeschke and Pyšek decided that more data are needed before a reasonable alternative hypothesis can be formulated.

Findings

Jeschke and Pyšek state that the “tens rule” is not based on a model or other defensible concept. It is also hampered by confusion of terms. Thus, different authors define the invasion process differently. Particularly confounding is the mixing of “impact” with steps in the invasion process. At the same time, there have been few studies of the “impact tens rule” hypothesis.

Finally, the “tens rule’s” predictions are not adjusted to consider changes in temporal and spatial scales. That is, it does not recognize that more invaders will be detected in any given place during more recent times than in the past. Furthermore, more invaders will find suitable niches in large areas than small.

The note that analysis is hampered by the paucity of reliable data about establishment success – especially for taxa other than mammals and birds. They do not discuss how this lack might affect efforts to analyze proportions of entering species that succeed in becoming invasive, especially among the small and inconspicuous taxa such as insects and fungal organisms that concern thus of us that focus on threats to forests. This same data gap has limited other studies as well; see, for example, Aukema et al. (2010) – who restricted their discussion of pathogens to “high impact” species.

Although Jeschke and Pyšek (2018) do not specify which studies they relied on to determine the proportion of successful invaders among species belonging to particular taxa, it seems likely that they relied principally on Vila et al. (2010) in determining that on average 25% invertebrates that are introduced (that is, proceed to the second stage in the process given above) become invasive. Vila et al. analyze introductions to Europe. They found that 24.2% of terrestrial invertebrates caused recognized economic impacts.

Jeschke and Pyšek (2018) Results and Discussion

Considering the “invasion tens rule”, two-thirds of the empirical tests in the dataset focused on the “invasion tens rule”. The majority of these focused on the transition from introduction to establishment (the transition from (ii) to (iii). The observed average percentage of species making this transition is more than 40% – or greater than four times larger than the “tens rule’s” prediction.

At the next transition, from establishment to spread (from iii to iv), the observed percentage of species making the transition is greater than 30% – or greater than three times the predicted value under the “tens rule”.

Considering the “impact tens rule”, on average a quarter of established non-indigenous species have a significant detrimental impact, which is again significantly more than the 1 out of 10 species predicted by the rule. Specifically by taxon, 18% of established plants have shown detrimental impacts. Among invertebrates and vertebrates that estimate is greater than 30%. All these observations are higher than predicted by the rule. However, sample sizes are low so more studies are needed to test whether these values hold true.

Regarding the fullest possible extent of the invasion process, 16 out of 100 species that were introduced (stage ii) had a significant impact. This is 16 times greater than the 1% predicted by the “tens rule”. Considering specific taxa, 6% of established plants and 15% of established invertebrates had a significant impact. Data were too poor to support an evaluation for vertebrates.

I note that the alarmingly high “impact” estimates for invertebrates are probably biased by scientists’ and funding entities’ lack of interest in species that don’t cause noticeable impacts.

Poor data preclude an analysis of the transition from transport (i) to introduced (ii).

Strengthening The Estimates

Might these introduction and impact estimates be tightened by analysis of additional sources, such as the studies led Seebens, forest pest impact analyses by Potter et al. (2019) and Fei (2019) and reviews of pest introduction numbers by Haack and Rabaglia (2013)?

Is it worth pursuing efforts to refine the Jeschke and Pyšek (2018) estimates? I think it is. An underestimation of the risk of introduction might lead decision-makers to downplay the need for a response.

Some scientists have accepted the new “rule of 25” (Schulz, Lucardi, and Marsico. 2021. Full citation at end of blog; also cited by USFS report – Poland et al. 2021). Others have not. Venette and Hutchison (2021; full reference at end of blog) continue to cite the estimate of approximately one “invasion success” for every 1,000 attempts – that is, a low-probability, high-consequence event. This challenges those responsible for managing invasive species.

Or are there other conundrums of introduction, establishment, and predicting impacts that have more direct relationship to improving programs? I note that the recent Forest Service report on invasive species (Poland et al. 2021) does not address the “rule of tens”.

Other Reasons Why Bioinvasion Damage is Underestimated

Jaric´ and G. Cvijanovic´ (2012) note that scientists lack a full understanding of ecosystem functioning, so they probably often miss more subtle – but still important – impacts.

Jeschke and Pyšek (2018) note that the percentage of introduced or established species with a quantifiable impact is not always the most important information. A single introduced species can have devastating impact by itself. They cite the amphibian disease chytrid (Batrachochytrium dendrobatidis) and such mammals as rats and cats.

SOURCES

Aukema, J.E., D.G. McCullough, B. Von Holle, A.M. Liebhold, K. Britton, & S.J. Frankel. 2010. Historical Accumulation of Nonindigenous Forest Pests in the Continental United States. Bioscience. December 2010 / Vol. 60 No. 11

Brockerhoff, E.G. and A. M. Liebhold. 2017. Ecology of forest insect invasions. Biol Invasions (2017) 19:3141–3159

Fei, S., R.S. Morin, C.M. Oswalt, and A.M. Liebhold. 2019. Biomass losses resulting from insect and disease invasions in United States forests. Proceedings of the National Academy of Sciences of the United States of America, 12 Aug 2019, 116(35):17371-17376

Haack, R.A. and R.A. Rabaglia. 2013 Exotic Bark and Ambrosia Beetles in the USA: Potential and Current Invaders. CAB International. 2013. Potential Invasive Pests of Agricultural Crops (ed. J. Pena)

Jaric´, I. and G. Cvijanovic´. 2012. The Tens Rule in Invasion Biology: Measure of a True Impact or Our Lack of Knowledge and Understanding? Environmental Management (2012) 50:979–981 DOI 10.1007/s00267-012-9951-1

Jeschke J.M. and P. Pyšek. 2018. Tens Rule. Chapter 13 of book by CABI posted at http://www.ibot.cas.cz/personal/pysek/pdf/Jeschke,%20Pysek-Tens%20rule_CABI%202018.pdf

Poland, T.M., Patel-Weynand, T., Finch, D., Miniat, C. F., and Lopez, V. (Eds) (2019), Invasive Species in Forests and Grasslands of the United States: A Comprehensive Science Synthesis for the United States Forest Sector. Springer Verlag. (in press).

Potter, K.M., M.E. Escanferla, R.M. Jetton, G. Man, and B.S. Crane. 2019. Prioritizing the conservation needs of United States tree species: Evaluating vulnerability to forest insect and disease threats. Global Ecology and Conservation. (2019)

Schulz, A.N., R.D. Lucardi, and T.D. Marsico. 2021. Strengthening the Ties That Bind: An Evaluation of Cross-disciplinary Communication Between Invasion Ecologists and Biological Control Researchers in Entomology. Annals of the Entomological Society of America · January 2021

Seebens, H., T.M. Blackburn, et al. 2018. Global rise in emerging alien species results from increased accessibility of new source pools. www.pnas.org/cgi/doi/10.1073/pnas.1719429115

Vilà, M., C. Basnou, P. Pyšek, M. Josefsson, P. Genovesi, S. Gollasch, W. Nentwig, S. Olenin, A. Roques, D. Roy, P.E. Hulme and DAISIE partners. 2010. How well do we understand the impacts of alien spp on ecosystem services? A pan-European, cross-taxa assessment. Frontiers in Ecology and the Environment, Vol. 8, No. 3 (April 2010), pp. 135-144

Venette R.C. and W.D. Hutchison. 2021. Invasive Insect Species: Global Challenges, Strategies & Opportunities. Front. Insect Sci.1:650520. doi: 10.3389/finsc.2021.650520

Williamson M.H. and K.C. Brown. 1986. The analysis and modelling of British invasions. Philosophical Transactions of the Royal Society of London Series B 314:505–522

Williamson M. and A. Fitter. 1996 The varying success of invaders. Ecology 77(6):1661–1666

Early Warning Systems – Are They Helping Prevent Introductions?

symptoms of tomato brown rugose fruit virus; Wikimedia

The US Department of Agriculture (USDA) is making efforts to strengthen pest prevention by setting up “early warning” systems. As part of this effort, the USDA-funded regional Integrated Pest Management Center in Raleigh, NC, has published a review of existing systems. These are intended to inform national phytosanitary agencies, such as APHIS, about pest species that might pose a threat to natural or agricultural resources. The ultimate goal is providing information that empowers the agency to enact effective preventive measures. [Noar et al. 2021. A full reference to the study is posted at the end of this blog.]

The review looked at six early warning systems’ goals, as well as their procedures for obtaining and disseminating information about potential threats. With one exception, these systems focus on plant pests.

The review did not undertake a rigorous analysis of the various programs’ efficacy.

The article points to the high economic costs associated with invasive plant pests. As a consequence of the huge volume of international trade – which is the principal vector of plant pests’ introduction – national phytosanitary agencies need information on which pests are moving most frequently, and on what commodities, so they can target the most risky pathways. The early warning systems are intended to do this before the pests are introduced to a new region. The several systems use different methodologies and criteria to identify such potential pests. They also are intended to raise awareness about high risk pests and pathways – but for different audiences.

Several of the early warning systems were set up and are managed by national phytosanitary agencies or their regional organizations. These include PestLens and the EPPO and NAPPO alert systems (described below). The article notes that these systems usually do not report diseases for which the causal agent has not been identified, because identification of the pathogen species is typically necessary before regulations can be adopted – and these are regulatory organizations. The authors do not analyze whether this constraint reduces the systems’ ability to provide timely warnings.

1. PestLens

PestLens is an early warning system set up by APHIS. It therefore focuses on pests that might become quarantine pests – that is, subject to regulation under terms of the Plant Protection Act. Such pests must pose a defined threat to US agricultural and natural resources. PestLens monitors more than 300 sources, including scientific journals, reports from national phytosanitary agencies, Google alerts, newspapers, e-mail lists and other plant-health-related websites. PensLens staff evaluate the information for relevance to APHIS based on: a) whether the information is new to APHIS; b) whether the plant pest is of quarantine significance to the US; c) its potential economic impact if introduced; d) the likelihood of a pathway for introduction; and e) the likelihood that action by APHIS might be needed to prevent its introduction. Information considered relevant includes indication that a pest is associated with a previously unknown host, has been detected in a new location, or has been eradicated from a country. The information has not necessarily been confirmed by the country (warning included in PestLens notices).

When the PestLens criteria are met, the analysts write a brief article including the new information and any existing background, such as previously known host range and distribution. These articles are compiled into a weekly e-mail notification sent to PPQ employees and thousands of other subscribers. They are also archived on the PestLens website. APHIS staff evaluate the information and make decisions as to whether some regulatory action is appropriate.

I am puzzled because some of the five criteria appear to require a pest risk analysis. Pest risk analysis is a complex task that I do not believe PestLens is equipped to carry out – certainly not as quickly as is required by an alert system.

Update

A review of PestLens (Meissner et al. 2015; full citation at end of the blog) describes the system more fully. It found that during the period October 2012 – October, 2014, 73% of PestLens articles were based on articles in scientific journals; 17% on federal, state, or regional governmental sources; 8% fon news media sources; and 3% on other sources. The principal government pest reports used were from the web sites of IPPC, EPPO & NAPPO.

The majority of PestLens articles reporting new locations, interceptions, and new hosts came from journals. New pest descriptions, new reports of an organism as a pest, and articles on research of interest came exclusively from journals. Articles on pest detections, outbreaks, and eradications came largely from government sources.

Meissner et al. analyzed APHIS’ response to PestLens notices. They said that certain APHIS actions, such as the implementation of official control programs, initiation of research activities, or the formation of specliazed task groups were not captured in this analysis. They found that over a ten month period in 2014, APHIS used the PestLens notices to update its pest databases 350 times; updated pest datasheets or pest profiles on the PPQ website 16 times; evaluated a pest’s regulatory status (e.g., prepared a risk assessment) 11 times; and revised its regulations 4 times.

Meissner et al. consider that it is vital to maintain up-to-date databases, especially regarding pest host and distribution ranges. Another benefit from the PestLens system is a set of metrics to improve accountability, for example identifying duplication of efforts and providing permanent records of when actions are taken (or declined) and the rationale.

2. EPPO Alert List and EPPO Reporting Service

The European and Mediterranean Plant Protection Organization (EPPO) has 52 member countries stretching from Russia and Uzbekistan to Spain, Algeria, and Morocco, and including their off-shore islands. EPPO maintains a pest Alert List of species chosen by the EPPO Secretariat based on the scientific literature and suggestions by member’s phytosanitary agencies. Factors leading to a listing include newly described pests, reports of spread to new geographical locations, and reports of major outbreaks in the EPPO region. Each listed pest has a fact sheet which contains known hosts and distribution, the type of damage, the mode of dissemination, and potential pathways for spread. Some pests are selected for pest risk analysis (PRA). Once the PRA is completed, the pest might be placed on the EPPO A1/A2 lists, which are species recommended for regulation by the member states. Pests not selected for PRA stay on the EPPO Alert List temporarily, typically three years, then their information is archived.

The EPPO Secretariat also publishes a monthly Reporting Service newsletter, which details phytosanitary events that might threaten the EPPO region, including both officially designated quarantine pests as well as emerging ones. Information includes new hosts, new geographical locations, new pests, and new identification and detection methods.

3. NAPPO Phytosanitary Alert System

The North American Plant Protection Organization (NAPPO) comprises Canada, the United States and Mexico. It has a web-based alert system that provides official pest reports from member countries. NAPPO also puts out Emerging Pest Alerts that contain news about plant pests and pathogens not established in this region. Sources are public, including scientific journals, newspapers, records from port interceptions, and domestic plant pest surveys. Generally NAPPO does not confirm its reports with the corresponding country’s phytosanitary agency.

4. IPPC Pest Reports

The International Plant Protection Convention (IPPC) has been ratified by more than 180 countries. The member countries’ phytosanitary agencies submit official pest reports concerning the occurrence, outbreak, spread, or eradication of organisms that are quarantine pests in that country or for neighboring countries and trading partners. These pest reports are posted on the IPPC website.

5. International Plant Sentinel Network

The International Plant Sentinel Network is a collaboration between the National Plant Diagnostic Network (NPDN) and the American Public Gardens Association. It is funded through cooperative agreements with APHIS under Section 10007 of the Farm Bill (Now Plant Protection Act §7721.) Launched in 2010, it has now grown to include more than 300 gardens across North America (information from the website).

The underlying premise is based on biogeography: plant-associated insects, fungi, and other pathogens introduced to plants that did not co-evolve with them (naïve plants) might cause unexpected damage. Since arboreta and botanical gardens cultivate many plant taxa outside their native range, they present an opportunity to observe new pest-host associations and the level of damage caused. Pests attacking native plants in North American botanical gardens might constitute “early detection” of a pest already in the country rather than a warning before the pest is introduced. Still, early detection is valuable.

6. ProMED

The Program for Monitoring Emerging Diseases (ProMED) is a program of the International Society for Infectious Diseases (ISID). ProMED was launched in 1994 as an Internet service to identify unusual health events related to emerging and re-emerging infectious diseases and toxins affecting humans, animals and plants. It focuses on outbreaks in new geographic regions, newly described diseases, and diseases for which the causal agent is unknown. By its own estimation, ProMED is the largest publicly-available system conducting global reporting of infectious diseases outbreaks (information from the website). ProMED maintains several e-mail lists that disseminate information pertaining to disease outbreaks; subscribers can choose among lists to fit their areas of interest and their geographic region. ProMED has a much broader scope than the other early warning systems. Also, it uses informal and nontraditional sources, including local media, on-the-ground experts, and professional networks.

Stakeholders can access much of the information on these websites and use them to report findings of new alien species to phytosanitary agencies.

Gaps

The review of early warning systems has disappointing gaps. First, I am puzzled that the authors looked only at the U.S.-based sentinel gardens effort and did not consider a parallel international network. The International Plant Sentinel Network was established in 2013. It is coordinated by the Botanical Garden Conservation Initiative, headquartered at Kew Gardens, United Kingdom. At present, 67 gardens and arboreta are participating; they are located in China, Australia and New Zealand, South Africa, South America, and Europe (including the Caucuses Mountains). After all, it is this international network that could inform APHIS about potential pests when they observe attacks on North American plants growing in their facilities. I confess that it is not clear to me whether participating gardens and arboreta would take the initiative to inform APHIS of pest attacks on North American plant species. It might be that APHIS would need to send inquiries to participants, probably focused on named pests. If these caveats are true, the network might not be a fully functional “early warning” body.

Update

Indeed, the USFS International Programs office is cooperating with the International Plant Sentinel Network to have some botanic gardens around the world monitor several North American species planted at their locations for disease and pest problems. In June 2021 the USFS sought suggestions from contacts on which North American tree species should be monitored. Candidates could be tree species of high economic, ecological, or urban/landscape value. The candidate list would probably be limited to 10 species. They should represent a diverse range of conifers and hardwoods.

Second, the articles authors make no mention of one of the principal sources of information on plant pests – CABI (Center for Agriculture and Bioscience International). CABI is a global source of information on organisms’ distribution. It is particularly strong in Commonwealth countries – which are important sources of plant material imported into the U.S.

Third, they apparently did not assess phytosanitary alert systems in place or anticipated in Australia, New Zealand, and South Africa. This is a significant gap since these countries are leaders on phytosanitary issues. They are also potential sources of damaging pests.

Most disappointing is the lack of analysis of programs’ efficacy and weaknesses. The only step in this direction is contrasting ProMED’s willingness to report diseases for which the causal agent is unknown. PestLens, EPPO, and NAPPO refuse to do this. We desperately need an analysis of the extent to which this narrow concept of the task limits the ability of these systems to provide early warnings.

At least several of the networks, including PestLens and NAPPO, do not limit themselves to information that has been confirmed by countries – which might be reluctant to admit the presence of a damaging organism on their turf.

I suggest that it would have been particularly instructive to analyze the reasons why Australia’s early warning efforts failed to detect introduction of the myrtle rust pathogen sufficiently early to facilitate eradication.

This review did discuss how several of the networks tracked the global movement of the Tomato brown rugose fruit virus (ToBRFV). The virus was first detected in Jordan in 2015; this was reported by PestLens in 2016. PestLens reported the virus had spread to Israel 2017. The NAPPO system then reported the virus in Mexico in 2018. The virus was detected in the United States in 2018, although difficulties in taking official samples and diagnosing the virus probably delayed awareness of this outbreak. APHIS restricted imports of tomato and pepper seed, transplants and fruits from countries where the virus was known to be present in November, 2019. Still, APHIS acted after the virus had been detected in the country. ToBRFV has continued to spread; it is now found in Asia, Europe, the Middle East, and northern Africa. I am not completely convinced that this episode illustrates successful utilization of early warning networks. Did the apparently tardy action by APHIS arise from overconfidence that the virus would be limited to the Middle East? Or is it attributable to rules which limit agency actions until official confirmation of the detection? Another actor might have been delay in proving that the virus was being spread by the international seed trade; international phytosanitary rules require agencies to define the introductory pathway before regulating.

I hope other scientists will undertake a more comprehensive analysis of early warning systems. We need our phytosanitary systems to be made as effective as possible. Further evaluation of current efforts would provide valuable insight.

[A separate article reporting on the international sentinel gardens network from a British perspective is Marfleet, K. and S. Sharrock. 2020. The International Plant Sentinel Network: an update on phase 2. The International Journal of Botanic Garden Horticulture.]

SOURCES

Meissner, H., J. Fritz, L. Kohl, H. Moylett, J. Moan, S. Emerine, and A. Kaye. 2015. PestLens: An early-warning system supporting U.S. safeguarding against exotic plant pests. Bull. OEPP 45: 304-310

Noar, R.D, C.J. Jahant-Miller, S. Emerine, and R. Hallberg. 2021. Early Warning Systems as a Component of IPM to Prevent the Intro of Exotic Pests. Journal of IPM, (2021) 12(1): 16; 1–7 doi: 10.1093/jipm/pmab011

Posted by Faith Campbell

The South African Report as a Model: U.S. Falls Short

Ailanthus – one of the invasive species shared by South Africa and the U.S.

A few years ago, I posted a blog in which I pointed to a report on South Africa’s response to bioinvasion as a model for the U.S. and other countries. South Africa has published its second report. This report outlines the country’s status as of December 2019 and trends since the first report (i.e. since December 2016). (I describe the report’s findings on South Africa’s invasive species situation in a companion blog.) Again, I find it a good model of how a country should report its invasive species status, efforts, and challenges. In comparison, many U.S. efforts comes up short.

U.S. Reports Need to Be More Comprehensive

The South African report provides a national perspective on all taxa. Various United States agencies have attempted something similar a few times. The report issued by the Office of Technology Assessment in 1993 summarized knowledge of introduced species and evaluated then-current management programs.

The 2018 report by the U.S. Geological Service focused on data: the authors concluded that 11,344 species had been introduced and described the situation in three regions – the “lower 48” states, Alaska, and Hawai`i. However, the USGS did not evaluate programs and policies. The new USDA Forest Service report (Poland et al. 2021) describes taxa and impacts of invasive species in forest and grassland biomes, including associated aquatic systems. Again, it does not evaluate the efficacy of programs and policies.

The biennial national reports required by the Executive Order establishing the National Invasive Species Council (NISC) are most similar to the South African ones in intent. However, none has been comprehensive. For example, the most recent, issued in 2018, strives to raise concern by stating that invasive species effect a wide range of ecosystem services that underpin human well-being and economic growth. Some emphasis is given to damage to infrastructure. The report then sets out priority actions in six areas: leadership and prioritization, coordination, raising awareness, removing barriers, assessing federal capacities, and fostering innovation. NISC also issued a report in 2016 – this one focused on improving early detection and rapid response. NISC posted a useful innovation – a “report card” updating progress on priority actions — in October 2018. It listed whether actions had been completed, were in progress, or were no longer applicable. However, the “report card” gave no explanation of the status of various actions; the most notable omissions concerned the actions dismissed as “not applicable”. Worse, no report cards have been posted since 2018. I doubt if those or any more comprehensive reports will be forthcoming. This reflects the increasing marginalization of NISC. The Council has never had sufficient power to coordinate agencies’ actions, and now barely survives.

U.S. Reports Need to Be More Candid

The authors of the South African report made an impressive commitment to honest evaluation of the country’s gaps, continuing problems, progress, and strengths. As in the first report, they are willing to note shortcomings, even of programs that enjoy broad political support (e.g., the Working for Water program).

It is not clear whether decision-makers have acted — or will act — on the report’s findings. That is true in many countries, including the United States. However, that is separate whether decision-makers have an honest appraisal on which to base action.

Assessment of South Africa’s Invasive Species Programs

Here is a summary of what the authors say about South Africa’s invasive species program. I want to state clearly that my intention is not to criticize South Africa’s efforts. No country has a perfect program, and South Africa faces many challenges. These have been exacerbated by COVD-19.

The report identifies the areas listed below as needing change or improvement.

1) Absence of a comprehensive policy on bioinvasion. Such a policy would provide a vision for what South Africa aspires to achieve, clarify the government’s position, guide decision-makers, and provide a basis for coordinating programs by all affected parties (e.g., including conservation and phytosanitary agencies).

2) As in the first report, the authors call for monitoring program outcomes (results) rather than inputs (money, staffing, etc.) or outputs (e.g., acres treated). The authors also say data must be available for scrutiny. In those cases when data are adequate for assessing programs’ efficacy, they indicate that the control effort is largely ineffective.

3) Inadequate data in several areas. The report notes progress in developing and applying transparent and science-based criteria to species categorization as invasive (as distinct from relying on expert opinion). However, this change is taking time to implement, and sometimes results in species receiving a different rating. [I agree with the report that data gaps undermine understanding of the extent and impacts of bioinvasion, domestic pathways of spread, justification of expenditures, assessment of various programs’ efficacy (individually or overall), priority setting, and identifying changes needed to overcome programs’ weaknesses. However, I think filling these data gaps might demand time and resources that could better be utilized to respond to invasions – even when those invasions are not fully understood.]

4) Funding of bioinvasion programs by the National Department of Forestry, Fisheries, and the Environment has been fairly constant over 2012–2019, but this is a decline in real terms. The figure of 1 billion ZAR does not include spending by other government departments, national and provincial conservation bodies, municipalities, non-governmental organizations, and the private sector. Authors of the report expect funding to decrease in the future because of competing needs.

While at least 237 invasive species are under some management (see Table 5.1), funding is heavily skewed – 45% of funding goes to management of one invasive plant (black wattle); 72% to management of 10 species.

5) Need for policies to address the threat emerging from rising trade with other African countries, especially considering the probable adoption of the proposed African Continental Free Trade Area. Under this agreement, imported goods will only be inspected for alien species at the first port of entry, and most African countries have limited inspection capacity. [European pathologists Brasier, Jung, and others have noted the same issue arising in Europe, where imported plants move freely around the European Union once approved for entry by one member state.]

The authors of the South African report say programs’ efficacy would be considerably improved if species and sites were prioritized, and species-specific management plans developed. They warn that, in the absence of planning and prioritization, there is a risk that funding could be diluted by targeting too many species, leading to ineffective control and a concomitant increase in impacts.

In South Africa, regulations, permits, and other measures aimed at regulating legal imports of listed species are increasingly effective. However, there is still insufficient capacity to prevent accidental or intentional illegal introductions of alien species. There is also more enforcement of regulations requiring landowners to control invasive species. Six criminal cases have been filed and – as of December 2019, one conviction (guilty plea) obtained. However, the data do not allow an assessment of the overall level of compliance.

The report found little discernable progress on the proportion of pathways that have formally approved management plans. Management is either absent or ineffective for 61% of pathways. There has been no action to manage the ballast water pathway. On the other hand, in some cases, other laws focus explicitly on pathways, e.g., agricultural produce is regulated under the Agricultural Pests Act of 1983.

During the period December 2016 – December 2019, the Plant Inspection Services tested more than 12,000 plant import samples for quarantine pests and made 62 interceptions. The report calls for more detailed information from the various government departments responsible for managing particular pathways (e.g., the phytosanitary service), and for an assessments of the quality of their interventions.

The number of non-native taxa with some form of management has grown by 40% since December 2016 – although – as I have already noted — spending is highly skewed to a few plant species. The number and extent of site-specific management plans has also increased, apparently largely due to a few large-scale plans developed by private landowners. However, few of these plans have been formally approved by some unspecified overseer.

Citing the strengths and weaknesses described above, the current (second) report downgraded its assessment of governmental programs from “substantial” to “partial”.

Comparison to U.S.

How does the United States measure up on the elements that need change or improvement? I know of no U.S. government report that is as blunt in assessing the efficacy of our programs –individually or as a whole.

Nevertheless, each of the five weaknesses identified for South Africa also exist in the United States:

Re: lack of a comprehensive policy, I think the U.S. also suffers this absence. This is regrettable since the National Invasive Species Council (NISC) was set up in 1999.
Re: monitoring outcomes to assess programs’ efficacy, I think U.S. agencies do seem to be more focused on collecting data on programs’ results – see the Forest Service’ budget justification. However, I think too often the data collected focus on inputs and outputs.
Re: data gaps, I think all countries – including the U.S. — lack data on important aspects of bioinvasion. I differ from the South African report, however, in arguing for funding research aimed at developing responses rather than monitoring to clarify the extent of a specific invasive species. Information that does not lead to action seems to me to be a luxury given the low level of funding.
Re: funding, I find that, despite the existence of NISC, it remains difficult to get an overall picture of U.S federal funding of invasive species programs. Indeed, the cross-cut budget was dropped in 2018 at the Administration’s request. I expect all agencies are under-funded; I have often said so as regards key USDA programs. As in South Africa, funding is skewed to a few species that I think should be lower in priority (e.g., gypsy moth).
Re: upgrading invasive species programs to counter free-trade policies, I think U.S. trade policies place too high a priority on promoting agricultural exports to the detriment of efforts to prevent forest pest introductions. This imbalance might be present with regard to other taxa and pathways. See Fading Forests II here.

South African and U.S. agencies also face the same over-arching issues. For example, the U.S. priority-setting process seems to be a “black box.” Several USFS scientists (Potter et al. 2019) spent considerable effort to develop a set of criteria for ranking action on tree species that are hosts of damaging introduced pests. Yet there is no evidence that this laudable project influenced priorities for USFS funding.

SOURCES

Potter, K.M., Escanferla, M.E., Jetton, R.M., Man, G., Crane, B.S. 2019. Prioritizing the conservation needs of United States tree species: Evaluating vulnerability to forest P&P threats, Global Ecology and Conservation (2019), doi: https://doi.org/10.1016/j.gecco.2019.e00622.

SANBI and CIB 2020. The status of bioinvasions and their management in South Africa in 2019. pp.71. South African National BD Institute, Kirstenbosch and DSI-NRF Centre of Excellence for Invasion Biology, Stellenbosch. http://dx.doi.org/10.5281/zenodo.3947613

Posted by Faith Campbell

South Africa & Invasive Species: Threats to High Value Biodiversity and Human Well-Being

*Protea repens* and fynbos vegetation near Table Mountain; photo by Mike Wingfield

South Africa is a country of immense biological diversity. It is also one that recognizes the threat invasive species pose to its natural wealth – and to the economy and livelihoods of ordinary people.

Also, South Africans are trying hard to improve the country’s invasive species program. It recently released the second national report assessing how well it is curtailing introductions and minimizing damage. As I describe in a companion blog, I find these reports to contain exceptionally thorough and honest appraisals of South Africa’s invasive species programs. I address that value in the companion blog, where I compare the South African report — and its findings — to U.S. government reports on our invasive species programs.

In South Africa, bioinvasion ranks third – after cultivation and land degradation – as a threat to the country’s impressive biodiversity. Invasive species are responsible for 25% of all biodiversity loss. Certain taxa are at particular risk: native amphibians and freshwater fishes, and some species of plants and butterflies.

Particularly disturbing is the bioinvasion threat to the Fynbos biome. The report notes that 251 non-native species have been identified in this system. This finding causes concern because the Fynbos is a unique floral biome. In fact, it constitutes the principal component of one of only six floral kingdoms found on Earth: the Cape Floral Kingdom (or region). For more information, go here.

map of South Africa showing fynbos biome

Not surprisingly, invasive bird and plant species are most numerous around major urban centers. The report concludes that this is probably because most non-native birds are commensal with humans; most birds and plants were first introduced to urban centers; and there is greater sampling effort there. Indeed, the patterns of (detected) invasive plant richness are still highly sensitive to sampling effort.

South Africa is considered a leader on invasive species management. However, its record is spotty.

Successes

Biocontrol interventions are considered a success. South Africa has approved release of 157 biocontrol agents, including seven since 2016. All the recent agents (and probably most others) target invasive plants. The South African biocontrol community conducts a comprehensive review of their effectiveness at roughly 10-year intervals. The fourth assessment is currently under way. Also, the report considers eradication of non-native fish (primarily sport species) from several wetlands and river reaches to have been successful. (However, opposition by sport fishermen has delayed listing of some trout species as invasive.)

Failures

On the other hand, strategies to combat invasive plants, other than by biocontrol, appear to be having little success. Even the extent of plant invasions in national parks is poorly documented. Also, the report highlights ballast water as an inadequately managed pathway of invasion.

The report estimates that three new non-native species arrive in South Africa accidentally or illegally every year. Interestingly, reported species arrivals have declined in the current decade compared to the preceding one. The report’s authors consider this to probably be an underestimate caused by the well-known lag in detecting and reporting introductions. The apparent decline also is contrary to global findings. Table 1 in Seebens et al. 2020 (full citation at end of blog) projected that the African continent would receive approximately 767 new alien species between 2005 and 2050.

Even the introductory pathways are poorly known: the pathway for 54% of the taxa introduced to South Africa are unknown. Of the species for which the introductory pathway is known, horticultural or ornamental introductions of plants dominate – 15% of that total. A second important pathway – for accidental introductions – is shipping (5% of all introductions). Other pathways thought to be prominent during 2017–2019 are the timber trade, contaminants on imported animals, and natural dispersal from other African countries where they had previously been introduced.

PSHB symptoms on Vachellia sieberiana; photo by Trudy Paap

Polyphagous shothole borer

The report highlights as an example of a recent introduction that of the polyphagous shothole borer (PSHB, Euwallacea fornicatus). https://www.dontmovefirewood.org/pest_pathogen/polyphagous-shot-hole-borer-html/ http://nivemnic.us/south-africas-unique-flora-put-at-risk-by-polyphagous-shot-hole-borer/ See Box 3.1 in the report. This species is expected to have huge impacts, especially in urban areas. While most of the trees affected so far are non-native (e.g., maples, planes, oaks, avocadoes), several native trees are also reproductive hosts. https://www.fabinet.up.ac.za/pshb In response to the introduction, the government established an interdepartmental steering committee, which has developed a consolidated strategy and action plan. However, as of October 2020 the shot hole borer had not been listed under invasive species regulations, even on an emergency basis. It had been listed as a quarantine pest of agricultural plants (e.g., avocado) per the Agricultural Pests Act 1983.

As note in my blog assessing the report, the report bravely concludes that the government’s regulatory regime is only partially successful (whereas three years ago it graded it as “substantial”). The downgrade is the result of a more thorough evaluation of the regulatory regime’s effectiveness.

SOURCES

Seebens, H., S. Bacher, T.M. Blackburn, C. Capinha, W. Dawson, S. Dullinger, P. Genovesi, P.E. Hulme, M. van Kleunen, I. Kühn, J.M. Jeschke, B. Lenzner, A.M. Liebhold, Z. Pattison, J. Perg, P. Pyšek, M. Winter, F. Essl. 2020. Projecting the continental accumulation of alien species through to 2050. Global Change Biology. 2020;00:1 -13 https://onlinelibrary.wiley.com/doi/10.1111/gcb.15333

Posted by Faith Campbell