invasive species – Page 7 – Center for Invasive Species Prevention

New USFS Report on Forest Health – Confusing Differences from Other Studies

ash killed by emerald ash borer
photo by Nate Siegert

USDA Forest Service has issued its annual summary of the nation’s forest health, based on various data sources.

The report seeks to provide status and trends at the national and regional levels as of 2017. It analyzes drivers of tree mortality including insects and pathogens, fire, and weather (especially drought). The report also discusses plant invasions in forests in the East. There is considerable discussion of emerging methods to improve data collection and analysis. Finally, it includes three case studies to illustrate the power of these approaches for analyzing forest health issues at specific sites:

• Decline of bishop pine (Pinus muricata) stands in California’s northern coastal areas;

• Impacts on naio (Myoporum sandwicense) on Hawaii’s Big Island of the myoporum thrips; and

• Impacts of increasing temperatures on Great Basin bristlecone pine (Pinus longaeva) communities.

Tree-Killing Insects and Pathogens

In 2017, the USFS Forest Health Protection (FHP’s) national Insect and Disease Survey (IDS) covered 55.1% of the total forested area of the lower 48 states. In Alaska, surveys covered about 7.3% of the total forested area. In Hawai`i, the surveys covered about 80.1 %.

The FHP program and partners in State agencies identified 63 mortality-causing agents and complexes that cumulatively affect 3.27 million hectares in the lower 48 states – 1.3% of the total 252 million hectares of forested land in these states. They also identified 50 defoliating agents and complexes affecting approximately 2.34 million hectares.

Most of the analyses focus on ecoregions developed by USFS scientists based on concepts put forward by Bailey (1995). Ecoregions are made up of regions with similar geology, climate, soils, potential natural vegetation, and natural communities. The area of the lower 48 states is divided into 190 ecoregions (see Chapter 1, esp. page 7).

Their damage, by type and level, was not evenly spread. Geographic hot spots of forest mortality were associated with bark beetle infestations in the West, and with emerald ash borer and southern pine beetle in the East. Hot spots of defoliation were associated with European gypsy moth and several native insects. Several native insects were the principal agents of defoliation in Alaska. In Hawai`i, about 37,000 hectares of mortality were listed officially as caused by an unknown agent, but the report attributes this mortality to rapid ‘ōhi‘a death.

The emerald ash borer was the most widespread single mortality agent in 2017, causing measurable tree mortality on 1.42 million hectares. In the program’s North Central region, 91% of the area suffering tree mortality was associated with the EAB. In one ecoregion – the Lake Whittlesey Glaciolacustrine Plain ecoregion (on the Ohio-Michigan border), about 73% of the mortality was caused by insects, especially the EAB. In a second, the Southwestern Great Lakes Morainal ecoregion (along the western shore of Lake Michigan in Wisconsin and Illinois), a quarter of the surveyed forest was experiencing exacerbated mortality due to EAB. The EAB also is causing mortality across 10,346 ha in the Northeast and more than 5,000 ha in the South.

However, heightened mortality (rates above 1%) in several Great Plains ecoregions were attributed largely to drought – even in the elm-ash-cottonwood forest type. However, such biological factors as oak decline, bur oak blight (Tubakia iowensis), Dutch elm disease, and native pests of ash were also significant. Emerald ash borer is mentioned rarely. I am confused by this finding – perhaps it reflects the fact that EAB has not yet been detected in North Dakota?

Other non-native pests that affect more than 5,000 ha in the lower 48 states were the Balsam woolly adelgid (20,758 hectares, primarily in the Northeast), beech bark disease (12,222 ha, primarily in the North Central region), oak wilt (9,573 ha, primarily in the North Central region), and sudden oak death (6,335 ha, in California). (All are described here.)

Still, despite the numerous and widespread presence of EAB and other non-native tree-killing insects and pathogens in the Central and Eastern States, in most areas, tree mortality is low relative to tree growth. Indeed, in nearly all the other North Central ecoregions, as well as those in the Northeast and South, 1% or less of the forested area was exposed to mortality agents. Hot spots associated with EAB were detected in Connecticut and eastern Kentucky.

Oak wilt was reported as a mortality agent in Michigan and Texas.

I am confused by the discrepancy between the findings of the Forest Health Protection (FHP’s) national Insect and Disease Survey and studies by other USFS scientists – as reported in earlier blogs. Thus, Randall Morin, speaking at the 81^st Northeastern Forest Pest Council in March 2019, reported detecting an approximate 5% increase in mortality – measured by tree volume – nation-wide. The greatest increases in mortality above the background rate was the four-fold increase for redbay and the three-fold increase for ash trees (from 0.8% to 2.7%), beech (from 0.7% to 2.1%), and hemlock (from 0.5% to 1.7%). (The increase for ash was incorrectly stated in my earlier blog).

Other studies by, among others, Guo et al. 2019 and the Potter studies discussed the threat – present and future – rather than current changes in mortality levels. See my blog here.

All note that their estimates are probably underestimates.

All the studies agree that EAB, European gypsy moth, and oak wilt threaten the greatest number of species (Potter et al. 2091b).

However, these reports also note the widespread presence of other damaging invaders – several of which don’t appear in the FHP survey. These include white pine blister rust (present in 94% of the potential hosts’ ranges; 955 counties); and dogwood anthracnose (in 609 counties in the East; plus uncalculated number of counties in the West) (Morin and the western counties were not calculated) (FIA “dashboards”).

whitebark pine in Crater Lake National Park killed by white pine blister rust
photo by F.T. Campbell

Data available from the West are less suited to the kind of analysis the FHP report used (for an explanation, see chapter 5). In the FHP West Coast and Interior West regions, principal mortality agents were bark beetles, drought, and fire. Some ecoregions suffered up to 5% mortality. Using a different measurement tool — annual mortality volume to gross annual volume growth (MRATIO) – the Southern California Mountain and Valley Ecoregion had the highest damage – at 2.50. This was attributed to a combination of prolonged drought, bark beetles, and fire.

Of 50 defoliation agents and complexes across the lower 48, the most widespread was the European gypsy moth. Across the continent, its impacts were detected on 39% of the total forested area of the lower 48 states (913,000 ha). Defoliation was particularly severe in the Northeast Region — again primarily by the European gypsy moth (869,000 ha). Other non-native defoliation agents affecting more than 5,000 ha in the lower 48 were the larch casebearer (25,891 ha in the North Central region, another 7,400 ha in the West Coast region) and winter moth (12,760 ha in the Northeast region). (The last is described here.)

The report concedes that death of tree species that are scattered in multi-species forests, such as most of the victims of non-native forest pests in the East, are not easily detected by the methodology the USFS uses. Examples cited by the report include emerald ash borer, hemlock woolly adelgid, laurel wilt, Dutch elm disease, white pine blister rust, and thousand cankers disease. (All are described here.)

Hence the authors advise decision-makers to use other forest health indicators in addition to this report.

I have already reported on studies by Morin, Liebhold, and colleagues and Kevin Potter and colleagues. Each finds ways to analyze Forest Inventory and Analysis (FIA) data to provide more detail on mortality caused by non-native insects and pathogens.

Invasive Plants

Invasive plants have already invaded a large proportion of rural forest in the East. Christopher Oswalt and colleagues used FIA data to assess the plant invasion status in 13 bioregions covering most of the temperate and boreal forests in the Eastern U.S. I blogged about Oswalt’s studies previously. Their findings are also reported here, in chapter 6:

Data were analyzed on 71 invasive plant species;
Half of the total area of 74 forest types was found to be invaded;

Plant invasions are almost twice as likely on privately than publicly owned land. Ownership alone was the deciding factor for the most-invaded forest types.)

The types of forest most heavily invaded were loblolly-shortleaf pine (61%), elm-ash-cottonwood (59%) oak-pine and oak-hickory (each 58%). The forest types least invaded were northern types: spruce-fir (20%), aspen-birch (32%), and maple-beech-birch (34%).

However, several forest type groups were excluded from the study; these included other eastern softwoods; pinyon-juniper; exotic softwoods; other hardwoods; woodland hardwoods; tropical hardwoods; and exotic hardwoods, and Fraser fir.

One-third of publicly owned (federal, state, and local) forest land was invaded, compared to 46% of private corporate forest and 59% of private non-corporate forest.

SOURCES

Bailey, R.G.. 1995. Descriptions of the ecoregions of the United States. 2d ed. Miscellaneous Publication No. 1391. Washington, D.C.: U.S. Department of Agriculture Forest Service. 108 p.

Fei, S., R.S. Morin, C.M. Oswalt, and A.M. 2019. Biomass losses resulting from insect and disease invasions in United States forests

Guo, Q., S. Feib, K.M. Potter, A.M. Liebhold, and J. Wenf. 2019. Tree diversity regulates forest pest invasion. PNAS. www.pnas.org/cgi/doi/10.1073/pnas.1821039116

Morin, R.S., K.W. Gottschalk, M.E. Ostry, A.M. Liebhold. 2018. Regional patterns of declining butternut (Juglans cinerea L.) suggest site characteristics for restoration. Ecology and Evolution.2018;8:546-559

Morin, R. A. Liebhold, S. Pugh, and S. Fie. 2019. Current Status of Hosts and Future Risk of EAB Across the Range of Ash: Online Tools for Broad-Scale Impact Assessment. Presentation at the 81^st Northeastern Forest Pest Council, West Chester, PA, March 14, 2019

Potter, K.M., B.S. Crane, W.W. Hargrove. 2017. A US national prioritization framework for tree species vulnerability to climate change. New Forests (2017) 48:275–300 DOI 10.1007/s11056-017-9569-5

Potter, K.M., M.E. Escanferla, R.M. Jetton, and G. Man. 2019a. Important Insect and Disease Threats to United States Tree Species and Geographic Patterns of Their Potential Impacts. Forests. 2019 10 304.

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

USDA Forest Service. Forest Health Monitoring: National Status, Trends, and Analysis 2018. General Technical Report SRS-239. June 2019. Editors Kevin M. Potter Barbara L. Conkling

What FIA data tell us about non-native pests of America’s forests

dead redbay in Claxton, GA 2009; photo by Scott Cameron

Several groups of scientists are using two large datasets to analyze impacts of invasion by non-native tree-killing pests. The first dataset used is official Forest Service monitoring data from the Forest Inventory and Analysis (FIA). These data are collected on a “rolling” annual basis from 130,210 forest plots in 2,098 counties in the 48 conterminous states. (Go here to learn more about FIA.)

The second dataset covers the distribution of non-native forest pests and is contained in the Alien Forest Pest Explorer database, also a Forest Service product.

Some of these studies (those led by Kevin Potter) have been carried out under the auspices of “Project CAPTURE” (Conservation Assessment and Prioritization of Forest Trees Under Risk of Extirpation) as part of a multi-partner effort to categorize and prioritize US tree species for conservation actions based on the threats and the trees’ ability to adapt to those threats. Partners include North Carolina State University; Forest Service Forest Health Protection, Southern Research Station, and forest health monitoring program; Eastern Forest Environmental Threat Assessment Center; and the Forest.Health program.

Here I highlight several key studies that use FIA data to examine:

1) the relationship between the diversity of forest tree species and the number of non-native insects and pathogens established there;

2) the mortality rate of forest trees due to non-native pests; and

3) impacts i in the form of “geographic hot spots;”

4) application of these findings to setting conservation priorities.

1. Impact of Host Diversity on Pest Establishment

One group of scientists (Guo et al.; reference at the end of this blog) extracted distribution data for 66 non-native pests (51 insects, 15 pathogens) taken from the Alien Forest Pest Explorer database. Then, the authors compared these pest’ distributions to FIA data on the diversity of tree species in the same invaded forests — for both “host” and non-host tree species. (Guo et al. classified a tree species as a “host” only if the relevant pest was present in the county.)

Guo et al. found that the number of alien pest species established in a county increased commensurate with tree diversity – as long as that tree diversity was fairly low, i.e., below 39 tree species. The number of established pests increased particularly strongly for specialist pests. However, at higher levels of tree diversity the number of established pests fell. Another factor was the diversity of non-host tree species present. When considering generalist pests, fewer pests became established when non-host tree diversity exceeded 15 species. When considering specialist pests, that cutoff was 25 species.

Among other possible factors explaining numbers of pests established, Guo et al. also found that only propagule pressure – measured by the proxy of human population density – had a significant positive correlation with increased pest numbers.

2. Measuring the Impacts of Non-Native Pests – Tree Mortality Data

A different approach has been undertaken by Randall Morin, working with a variety of coauthors. Dr. Morin has used FIA survey data to detect whether the impact of various non-native pests can be seen in heightened levels of mortality of the pests’ hosts. I reported these findings in a previous blog.

eastern hemlock killed by hemlock woolly adelgid in Nova Scotia
photo by Celia Boone, Nova Scotia Department of Lands and Forestry

As I noted in the earlier blog, Dr. Morin found that non-native forest pests had caused an approximately 5% increase in total mortality by tree volume nation-wide. The degree to which mortality levels rose in any county depended on the killing power of the individual pest species and the relative density of tree species vulnerable to the pests present. The number or diversity of non-native tree-killing pests established in the county (see the Guo et al. study) did not determine the county’s morality level. See maps in the earlier blog.

The greatest increase in mortality rates (a four-fold increase) was for redbay, under attack by laurel wilt disease. Three-fold increases in annual mortality rates were detected for ash, beech, and hemlock. To learn the specific mortality rates for individual pest-host relationships, visit here and read the descriptions of butternut, chestnut, redbay, beech, hemlock, ash, tanoak (sudden oak death), Port-Orford cedar, oak wilt, and European gypsy moth

tanoak killed by sudden oak death (Phytophthora ramorum), Big Sur, California

3.Overview of Impacts, Identification of Geographic “Hotspots” and Use in Setting Conservation Priorities

To carry out “Project CAPTURE,” Potter, Escanferla, Jetton, and Man 2019a (full reference at the end of this blog) sought to identify regions at greatest risk of significant ecological and economic impacts from damaging insects, pathogens, or parasitic plants, especially non-native, introduced pests.

They first compiled a list of 339 serious pests threatening one or more of 419 native tree species in the continental United States. The list comprised 168 diseases, 151 insects, and 20 parasitic higher plants. It included both native and introduced pests – 142 native, 55 non-native, and 142 of unknown or disputed origin.

They analyzed up to five of the most serious pests for each native tree species. This analysis resulted in 1,378 pest-host combinations.

The authors assigned a severity rating for each pest-host combination. Instead of using counties, as Guo et al. did, they evaluated pests and hosts in hexagons covering approximately 800km². They used FIA data to determine in which hexagons each pest-host combination is present. Finally, the authors determined the “importance value at risk” (IVAR) for each hexagon based on the number of pest-host combinations present and the relative severity of those combinations. [See the article – referenced below – for detailed explanations of these calculations.]

General Findings

Analyses addressing all the pests, including native ones, found different results than analyses focused on the non-native pests. Thus, analyses of all pests found greater impacts in the West, whereas non-native pests caused potentially greater impacts in the East. The authors note that the non-native pest risk could be greatly magnified across much of the eastern United States if the alien pests are able to spread to the entirety of their hosts’ ranges.

Considering the pests:

Of the 1,378 host/agent combinations, 51.5% involve diseases, 43.6% involve insects, and 4.9% involve parasitic plants.
Among the insects, 77 are phloem or wood-borers, 51 are foliage-feeders, and 23 are sap-feeders. Of the total of 601 insect-host combinations (both native and exotic), borers are the agents in 224 (37%) of the combinations.
54% of the host tree species (228) are infested by an exotic pest – although only 28% of the 1,378 host/agent combinations involved known exotic pests.

Considering the host tree species:

two non-native pests affect the largest number of hosts: European gypsy moth – 65 hosts; and oak wilt (Bretziella fagacearum) – 61 hosts. A third alien species, Asian longhorned beetle, ranked fourth overall with 43 hosts.
Nearly 70% of the host/agent combinations involve angiosperm species, 30% gymnosperms. Regarding all combinations, the severity of the gymnosperm/agent combinations was significantly higher than angiosperm/agent combinations. However, when considering only non-native pests, the opposite was true: host/agent combinations for angiosperms had greater average severity.

Severity of Impacts

Disease impacts are more severe, on average, than insect pests.
Wood-borers are more damaging than other types of insect pests.
Exotic agents have, on average, considerably more severe impacts than native pests.
The risk estimate – especially for the East – is an underestimate because established pests could spread to additional vulnerable areas and there is a high likelihood that new pests will be introduced.

Of the 15 host-agent combinations with the highest severity, seven are caused by an insect, seven by a disease, one by an insect-disease complex. These 15 tree species at highest risk are:

Florida torreya (Torreya taxifolia) – pathogen,
American chestnut (Castanea dentata) – pathogen,
Allegheny chinquapin (C. pumila) – pathogen,
Ozark chinquapin (C. pumila var. ozarkensis) – pathogen,
redbay (Persea borbonia) – disease complex,
Carolina ash (Fraxinus caroliniana) – insect,
pumpkin ash (F. profunda) – insect,
Carolina hemlock (Tsuga caroliniana) – insect,
Port-Orford cedar (Chamaecyparis lawsoniana) – pathogen,
tanoak (Notholithocarpus densiflorus) – pathogen,
butternut (Juglans cinerea) – pathogen,
eastern hemlock (Tsuga canadensis) – insect,
white ash (Fraxinus americana) – insect,
black ash (F. nigra) – insect, and
green ash (F. pennsylvanica) – insect.

emerald ash borer – cause of threat to five of the “top 15”

Four host families are at the highest risk to alien pests, as measured by both the numbers of tree species affected and by the most host/agent combinations – Fagaceae (oaks, tanoaks, chestnuts, beech); Pinaceae (pines); Sapindaceae (soapberry family; includes maples, Aesculus (buckeye, horsechestnut); Salicaceae (willows, poplars, aspens). The authors point out that these families comprise the most tree species in North America and that the species are widespread.

The families under greatest threat varied somewhat when measured by the severity of the host/pest threat. While Fagaceae was still at greatest risk, and Sapindaceae was still in the top four, Ulmaceae (elms) and Oleaceae (includes Fraxinus) replaced pines and willows.

Analyses addressing all the pests found geographic “hotspots” only in the West. Analyses addressing non-native pests, based on their current extent, also resulted in Western areas appearing at highest risk. However, analyses addressing non-native pests but assuming that these pests had spread to the full extent of their hosts revealed “hotspots” in the Northeast and Great Lakes States. The Southeast is consistently a “coldspot” – clearly the near extirpation of one understory tree – redbay – is not sufficient to affect top-level data.

Note that none of the maps in the article shows all exotic pests separately from native pests; even the map in Figure 4b illustrates non-native insects only. Dr. Potter has told me that it proved too difficult to determine the origin of many pathogens (K. Potter pers. comm. April 2019).

Setting Conservation Priorities

In a second publication, Potter Escanferla, Jetton, Man, and Crane (2019b) applied the severity ranking for host-pest relationships to set priorities for conservation actions targetting the host – especially conservation of genetic diversity and implementation of programs aimed at enhancing hosts’ resistance to the pest through breeding.

They created 11 classes of species based on three factors:

each tree species’ exposure to an extrinsic threat – as measured by the extent to which a threat could diminish a species’ adaptive genetic variation;
each tree species’ sensitivity to the threat – as indicated by the species’ rarity, and size of range, or the degree to which a species’ total genetic resource base is susceptible to a threat; and
each species’ ability to adapt to the pest threat – as determined by extent to which a species is unable to adapt, through micro-evolutionary change and phenotypic plasticity; unable to maintain evolutionary resilience

(These definitions are taken from Potter, Crane, and Hargrove 2017; reference below)

The highest ranked species (in three classes) are the 15 listed above.

How to Use These Data / Findings

The purpose of the CAPTURE project is to guide USDA Forest Service prioritization of forest tree species and populations for genetic conservation and monitoring efforts. It began as a response to a request from the National Forest System regional geneticist in the Southern Region (Region 8); it was then expanded to the entire country – including Puerto Rico, the Virgin Islands, and Hawai`i. (Dr. Potter told me that he has most of the data needed for Hawai`i, but is still collecting data for the Caribbean. He still needs to query experts in order to customize the framework for the two regions.)

Now that the project has set priorities for continental species, it will be interesting to see the extent to which these findings guide actual allocation of resources. For example, will additional resources be assigned to protecting such non-commercial species as Florida torreya and redbay? Will existing resistance breeding efforts – which mostly struggle to obtain funding – now have better access to funds?

The Forest.Health project – which promotes use of biotechnology to breed resistant hosts – has adopted the priority list.

Potter et al. 2019b call also for incorporating their findings into regular national reports such as those issued per the Resources Planning Act Assessment and the National Report on Sustainable Forests. These data are essential to assessing the degree to which U.S. forests can continue to meet demand for a broad range of goods and services, safeguard biological diversity, and contribute to the resilience of ecosystems and economies.

I hope that the data on regeneration, growth, and succession of individual species compiled by Morin, et al., — which are not part of the CAPTURE project — would also be included in such reports.

I applaud these studies and hope they will prove influential. They avoid some of the flaws in other priority-setting processes, which tend to focus on species with commercial value. However, I would like to suggest that some other factors should also be included in calculating priorities:

Are some host species especially significant in their ecosystems? That is:
- Do some create unique biomes, e.g., hemlocks in stream valleys in the middle and southern Appalachians; Fraser fir (and red spruce) on southern Appalachian mountain tops; black ash in wooded swamps from Minnesota to New Brunswick; Port-Orford cedar as part of the unique flora of the serpentine soils of the Siskiyou Mountains; whitebark pine at high elevations of Western mountains.
- Are some hosts important providers of rare resources, e.g., hard mast – tanoak in California coniferous forests, beech in northern part of its range, whitebark pine at high elevations. Or calcium to the leaf litter and soil – e.g., dogwoods.
- Are particularly high numbers of faunal species associated with the host? Or rare fauna?
Should pests that threaten entire genera – or monotypic genera – receive a higher priority? E.g., emerald ash borer threatening Fraxinus; Phytophthora ramorum threatening tanoak?

SOURCES

Guo, Q., S. Feib, K.M. Potter, A.M. Liebhold, and J. Wenf. 2019. Tree diversity regulates forest pest invasion. PNAS. www.pnas.org/cgi/doi/10.1073/pnas.1821039116

Potter, K.M., B.S. Crane, W.W. Hargrove. 2017. A US national prioritization framework for tree species vulnerability to climate change. New Forests (2017) 48:275–300 DOI 10.1007/s11056-017-9569-5

New Study of Why People Move Firewood – and Its Relation to EAB Deregulation

We know that people moving firewood long distances is cause for great concern because of the likelihood that tree-killing pests will be transported to new and previously uninfested locations. This concern has been heightened by the USDA APHIS proposal to deregulate the emerald ash borer (EAB). As the principal federal “quarantine pest” transported by firewood, the EAB provides the legal foundation for most federal and state firewood regulations. (Of course, the EAB regulations also govern other articles that could transport wood-boring pests). (See earlier blogs here and here.)

Most forest pest professionals agree that the greatest risks are associated with individuals who transport firewood for recreational camping or summer homes. These people have proven to be the most difficult to regulate and the most likely to not see – or to ignore – messages intended to discourage them from moving firewood. The Nature Conservancy manages the “Don’t Move Firewood” program. It has done polling on messages and impact and concludes that the percentage of U.S. voters who have heard a “don’t move firewood” message remains steady and that those who have heard that message are less likely to transport firewood, especially over distances greater than 50 miles. More details are here

A recently published study by several academics and one forest service scientist reinforces The Conservancy’s earlier conclusion about the importance of outreach efforts as an essential component of programs intended to manage wood-boring pests. On the other hand, the new study points to additional nuances in crafting messages that will be effective in changing people’s behavior.

Findings

Daigle et al. 2018 (see full citation at the end of the blog) surveyed 272 people who were camping in public (state) or private campgrounds in three New England states in 2013 – four years after each of those states adopted regulations prohibiting out-of-state firewood and began their outreach efforts. Some campers apparently feel a strong connection to the place they are visiting, as shown by the fact that 84% of the 79 campers at private campgrounds had spent two or more nights camping in the same state in the previous year. That emotional connection might provide a motivation that could be activated to persuade those campers to stop transporting firewood (see below).

The authors found that slightly more than 25% of the 272 respondents reported that they often or always brought firewood from home for camping. More discouraging is that they found that people might not comply even when informed about the risks. Instead, compliance depended largely on the individual’s motivation and commitment level rather than knowledge. Worse yet, campers categorized as “highly involved” in the forest pest issue were just as likely to transport firewood from home as were others. Apparently, these non-compliant campers did not fully “connect the dots” between their concerns about forest health and their own actions. See below for Daigle et al.’s suggestions for ways to help people make those connections.

To understand the role of motivation, Daigle et al. tried to assess the strength of each camper’s beliefs about the relationship between tree-killing pests and the transport of firewood by recreational campers.

Overall, 25% of respondents were very highly involved with tree pest issues; another 22% were highly involved. Respondents’ perception of the relationship between damaging tree pests and transport of firewood differed significantly based on their levels of involvement. Respondents with a low level of involvement were less likely to agree with three statements (listed below) that firewood-associated pests pose a serious threat. Campers with very high levels of involvement strongly disagreed with three other statements that either downplayed the threat or portrayed the respondent’s compliance as “useless” as long as others continue to transport firewood.

Perception questions against which respondents’ agreement or disagreement was measured:

“There is not much one individual can do about invasive pests brought in by firewood”
“I don’t think invasive pests brought in by firewood are very important.”
“The threat of invasive pests brought in by firewood is serious.”
“As long as other people continue to bring firewood from home, my efforts to prevent invasive pests are useless.”
“The invasive forest pest risk from firewood is exaggerated.”
“In the long run, things will balance out with invasive pests.”

Rationale

Respondents’ most frequent explanations for why they take firewood from home when they go camping were cost, quality, and convenience. The most frequently cited reason for not transporting firewood was that the respondent knew that it was not allowed.

Level of pest awareness:

While nearly all respondents (92%) had heard something about non-native pests killing trees, but 57% could not recall the name of a specific pest in the absence of a prompt. When asked about the emerald ash borer and Asian longhorned beetle, more respondents had heard about the ALB (77% v. 52%). Most said the principal source of information was a state agency.

Suggested Actions

Daigle et al. conclude that authorities need to increase citizens’ exposure to outreach materials in order to activate concern and bring about desired actions to curtail risk of pests in firewood.

One clear need is to counter many campers’ belief that their wood is safe so it is okay to transport it regardless of the regulations. Often they based that belief on the fact that their home is not in a designated quarantine zone. Daigle et al. suggested that educational material should try to counter this belief by emphasizing the time lag between a pest’s establishment and its detection.

To help “connect the dots” between campers’ concerns about forest health and the implications of their actions (transporting firewood), survey respondents suggested using more visuals showing the destruction caused by the invasive forest pests, especially in areas they care about – close to home or favorite recreation areas. Daigle et al. thought such pictures would “help the campers with high involvement to trigger activation of attitudes with the association of forest pests and firewood transport.”

Other suggestions for strengthening outreach were to ensure that the message

Is novel – that it does not simply reiterate a camper’s initial belief system.
Produces agreement by the recipient without generating counterarguments.
Is relevant to the audience’s concerns.

They also suggested that campgrounds (public and private) help motivate campers to leave firewood at home by coordinating with local firewood vendors to provide competitively priced firewood at the campground or by including the cost of providing some firewood in the camping fee.

Daigle et al. made two other suggestions that call for stronger actions.

First, they suggested that outreach programs incorporate incentives or rewards to engage people who don’t have a high level of involvement in forest health issues.

Second, they suggested that authorities reinforce the educational message by using “more direct” actions, such as

confiscating illegally transported firewood at check stations,
issuing warnings about such actions, or
administering fines for moving non-compliant firewood.

The authors suggest that state agencies should consider taking these actions – but I see no reason why federal agencies should not also.

EAB; David Cappaert

Conclusions re APHIS’ Proposal to Deregulate EAB

Daigle et al. conclude that outreach efforts aimed at curtailing movement of firewood need to be continued. They are a critical component of overall management programs targetting non-native tree-killing pests – programs developed through decades of research and trials. The motive is clear: more effectively delaying these pests’ spread provides large benefits to municipalities and homeowners.

These are the same points made by many who opposed APHIS’ proposal to deregulate the emerald ash borer.

In its comments to APHIS, The Nature Conservancy noted that the domestic EAB quarantine had been effective in limiting spread of the pest through two of the most important pathways – firewood and nursery stock. The resulting slower spread had protected three-quarters of the ash range in the United States and bought time to develop mitigation measures.

Further, eliminating the federal quarantine would not only unleash this pathway for long-range movement of EAB but undermine the many federal, state, regional, tribal, private, and non-profit partners’ efforts to curtail movement of all invasive forest pests in firewood.

Many other commenters, including several state agencies, the National Association of State Foresters and Southern Group of State Foresters called for APHIS to continue leading national efforts to curtail spread of EAB and other pests through careless movement of infested firewood. The Montana Department of Natural Resources and Conservation and NASF specifically urged that APHIS reinstate the National Firewood Task Force (which APHIS led in 2009-2010).

The Don’t Move Firewood program has a more informal blog on this topic, available here.

Source

Daigle, J.J., C.L. Straub, J.E. Leahy, S.M.De Urioste-Stone, D.J. Ranco, N.W. Siegert. How Campers’ Beliefs about Forest Pests Affect Firewood Transport Behavior An Application of Involvement Theory. Forest Science XX(XX):1-10 https://academic.oup.com/forestscience/advance-article/doi/10.1093/forsci/fxy056/5232804

South African report: Rigorous, Honest, and a Model for U.S. and Others

Density of invasive plants in South Africa

map available here

Last month, in my blog about the US Geological Survey’s report on invasive species I announced release of a report by South Africa on its invasive species management programs – available here. Because this report is unusual in both its rigor and its honesty, I’m returning to it here. I think it is a model for our country and others.

The report provides the basics. That is, it analyzes pathways of introduction and spread; number, distribution and impact of individual species; species richness and abundance of alien species in defined areas; and the effectiveness of interventions. Of the 775 invasive species identified to date, 556, or about 72%, are listed under some national regulatory program. Terrestrial and freshwater plants number 574 species; terrestrial invertebrates number 107 species. A different set of 107 species, or about 14%, are considered by experts to be having major or severe impacts on biodiversity and/or human wellbeing. The highest numbers of alien species are in the savanna, grassland, Indian Ocean coastal belt, and fynbos biomes. South Africans are particularly focused on the reductions in surface water resulting from plant invasions. Much of the control effort is under the egis of the decades-old “Working for Water” program.

Also, the report has features that are all-too-rare in work of its kind. First is the authors’ focus on rigor – of data sources and interpretation of those data using standardized criteria. Second – and even more important – is their call for analyzing the efficacy of the components of invasive species program. They insist on the need to measure outcomes (that is, results), not just inputs (resources committed) and outputs (“acres treated”, etc.). Inputs are far easier to measure and are, unfortunately, the mainstay of how most U.S. efforts are tracked – if they are tracked at all.

As they note, measure of inputs and outputs are not useful because they provide no guidance on the purpose of the action or treatment or of its effectiveness in achieving that purpose.

(For earlier CISP advocacy of measuring outcomes, visit the National Environmental Coalition on Invasive Species and read the bullet points under “Recommendations for a Comprehensive National Response”.)

The report has been praised by international conservationists, including Piero Genovesi – chair of the IUCN’s Invasive Species Specialist Group. British ecologist Helen Roy says that, to her knowledge, it is “the first comprehensive synthesis of the state of invasive species by any country.”

How well are programs working?

The authors’ focus on rigor includes being scrupulously honest in their assessments of current program components. They note deficiencies and disappointments, even when the conclusions might be politically inconvenient. To be fair, all countries struggle to achieve success in managing bioinvasions. And South Africa is, in many ways, a developing country with a myriad of economic and social challenges.

So it is probably not surprising that, for most factors analyzed, the authors say data are insufficient to determine the program’s impact. Where data are adequate, they often show that programs fall short. For example, they conclude that control measures have been effective in reducing populations of established invasive species, usually plants, in some localized areas but not in others. While the situation would arguably have been worse had there been no control, current control efforts have not been effective in preventing the ongoing spread of IAS when viewed at a national scale. Only one of South Africa’s 72 international ports of entry has consistent inspection of incoming air passengers and cargo – and even those inspections are not carried out outside of regular working hours (e.g., nights and weekends).

The authors are even critical of the “Working for Water” program – which is the basis for most control efforts in South Africa and enjoys wide political support. WfW has two goals: providing employment and development opportunities to disadvantaged individuals in rural areas, and managing invasive alien plants. Despite substantial funding, the WfW program has supported control teams that have reached only 2% – 5% of the estimated extent of the most important invasive plants. Furthermore, programs structured to provide employment have not ensured use of the most efficient control strategies.

What’s needed in South Africa — and around the world

The authors conclude that South Africa needs new processes to monitor and report on bioinvasions in order to achieve evidence-based policy and management decisions. They call for (1) more research to determine and assess invasive species impacts; (2) better monitoring of the effectiveness of current control measures; and (3) the development of methods to look at the impact of bioinvasions and their management on society as a whole.

The authors say it is important for South Africa to improve its management of invasive species because their impacts are already large and are likely to increase significantly. They note that improving management efficiency will require difficult choices and trade-offs. They recommend a focus on priority pathways, species, and areas. They also stress return on investment.

I don’t know how this report has been received in South Africa. I hope government officials, media observers, landowners, political parties, and other stakeholders appreciate the honesty and expertise involved. I hope they take the analyses and recommendations seriously and act on them.

(Preparation of the report was was overseen by a team of editors and contributing authors employed by the South African National Biological Diversity Institute (SANBI) and the DST-NRF Centre of Excellence for Invasion Biology at (C.I.B). Drafts were widely circulated to contributing authors and other stakeholders for comments. An independent review editor will be appointed to assess the review process and recommend any ways to strengthen the process for future reports.)

Meanwhile, how do we Americans apply the same rigor to analyzing our own efforts?

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.

Report Lists Non-Native Species in the U.S.

Ailanthus altissima

Several scientists at the United States Geological Service (USGS) have published a report and accompanying datasets that attempts to provide a publicly accessible and comprehensive list of non-native species established in United States.

Led by Annie Simpson and Meghan C. Eyler, a team of six scientists worked six years (2013–2018). They reviewed 1,166 authoritative sources to develop a list of 11,344 unique names – most of them binomials (genus and species), a few genera, plus some viruses.

This was a Herculean effort that produced very valuable products. We are all in their dept!

Simpson and Eyler point out that knowing which species are non-native to a region is a first step to managing invasive species. Lists compiled in the past were developed to serve a variety of purposes, including watch lists for preventing invasions, inventory and monitoring lists for research and modeling, regulatory lists for species control, and non-regulatory lists for raising awareness. As a result, they are not comprehensive.

Among the sources these authors consulted in preparing the list were peer-reviewed journal articles, books, brochures, circulars, databases, environmental assessments, technical reports, graduate theses, and websites.

Data – by Region

The report also notes which non-native species were established in each of three regions: the “lower 48” states, Alaska, and Hawai`i. Not surprisingly, more than half the non-native taxa are established in the vast area (nearly 7.9 million km²) comprising the “lower 48” states – 6,675 taxa. Almost half of the total number of non-native taxa have established in the tiny geographic region (only 28,311 km²) of Hawai`i – 5,848 taxa. One-tenth as many non-native taxa – 598 – are reported as established in Alaska (1.7 million km²).

This report includes taxa that are not native to any part of the specific region, but established (naturalized) somewhere in the region. An “established” species must have at least one population that is successfully reproducing or breeding in natural systems. The list includes domesticated animals and plants introduced for crops or horticulture when the taxon has escaped cultivation or captivity and become established in the wild. Species listed range from feral hogs (Sus scrofa) to plum pox virus and citrus canker to ohia rust (Puccinia psidii).

Of the total 11,344 taxa, 157 are established in all three regions. These included 125 vascular plants (especially grasses and asters); 13 arthropods, 11 mammals; 6 birds; 3 mollusks; 1 bryozoan. One of the ubiquitous plant species is tree of heaven (Ailanthus altissima). I find it entirely appropriate that the cover photo shows this tree – the photo was taken 8 miles from my home in Fairfax County, Virginia.

Nearly three-quarters (71.4%) of the non-native species in Alaska are plant species. More than half (59.7%) of the non-native species in the “lower 48” region are also plants. Nearly all the remainder of the non-native species in both regions are some kind of animal. Fungi constitute only 1.8% of the non-native species in the “lower 48” region; all the rest of the groups (Bacteria, Chromista, Protozoa, Virus) constitute less than 1% of the non-native species recorded in either region.

By contrast, in Hawai`i, animals make up 69.7% of the listed non-native species; most are invertebrates. Plants constitute 29.8% of the Hawaiian list.

Gaps, by Taxon

The authors recognize that invertebrates and microbes are under-represented because species are still being discovered; non-charismatic and difficult-to-identify species tend to be overlooked; and the species composition of any nation in this era of globalization is constantly subject to change.

I have noted some gaps among the pathogens: the absence of some of the Phytophthora that have been detected infecting shrubs and herbaceous plants in California, e.g., Phytophthora cambivora, siskiyouensis, tentaculata; and the “rapid ohia death” pathogens, Ceratocystis huliohia and C. lukuohia. Dr. Simpson is aware of these gaps and is soliciting sources to help add these organisms – especially the various Phytophthora species – to the next version of the list.

Simpson and Eyler note that the relative geographic distribution of the list at its current state seems to reinforce three well established premises: that tropical island systems are particularly vulnerable; that higher latitudes host fewer but are not invulnerable; and that species diversity in general decreases with increasing latitude.

Comparisons to Other Databases

After standardizing the names in the list by comparing them to the Integrated Taxonomic Information System (ITIS), Simpson and Eyler also reviewed the USGS BISON database, which has more than 381 million occurrence records for native and non-native species in the U.S. and Canada, covering 427,123 different taxa. (The BISON database contains significantly more species occurrences for the U.S. than the largest invasive species database, EDDMapS, which contained 4.4 million species occurrences as of June 2018.) Simpson and Eyler had to evaluate which of these taxa met their definition of non-native, since most species occurrence records in the USGS BISON are not labeled as non-native in the original records.

Comparing the BISON and non-native lists, Simpson and Eyler found that the BISON list contained a larger number of occurrence records for non-native taxa: a total of 13,450,515.However, the BISON list does not provide complete coverage of non-native species: it includes records for 77% of list of non-native species Simpson and Eyler found in Alaska, 75% of the “lower 48” sublist, but only 37% of the Hawaiian sublist.

Simpson and Eyler state their intention to continue updating the list of non-native species, they welcome contributions to it from area experts, and they urge integration of new occurrence data into invasive species database such as EDDMapS.

Indicators of Non-Native Species Richness

Figure 3 in the report (above) maps the number of non-native taxa in BISON at the county level. Figure 4 displays the proportion of non-native to native species in BISON. Higher percentages are generally evident in coastal areas and other regional hotspots. For example, the proportion in Hawaiian counties is greater than 33%. Additional data are needed to perform a more in-depth analysis of non-native species richness and abundance.

UPDATE! New Report in the Works

In June 2021, USGS announced that it was updating its Comprehensive List of Non-Native Species Established in 3 Major Regions of the U.S. so that the document more closely aligns with the parameters of the Global Register of Introduced and Invasive Species. The new USGS dataset is to be called the US Register of Introduced and Invasive Species. The list in the current draft includes 15,364 records. About 500 of these records are in Alaska, 6,000 in Hawai`i, and 8,700 in the conterminous 48 States.

One of the lead authors, Annie Simpson, contacted invasive species experts seeking feedback and suggested additions – based on authoritative resources such as peer reviewed journal articles, pest alerts, databases, books, and technical bulletins. She sought input by 25 July, 2021.

The published version of this dataset will be made freely available on USGS’ ScienceBase (https://www.sciencebase.gov), and all reviewers will be acknowledged in the dataset’s abstract.

SOURCE

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.

The report and accompanying data tables are available here.

South African report

In an unrelated but similar development, South Africa has issued a report on its invasive species — 2017 The Status of Biological Invasions and Their Management in South Africa. The report analyzes pathways of introduction and spread; number, distribution and impact of individual species; species richness and abundance of alien species in defined areas; and the effectiveness of interventions. The report notes that 775 invasive species have been identified to date, of which 556 are listed under some national regulatory program. Terrestrial and freshwater plants number 574 species; terrestrial invertebrates number 107 species. (This total does not include the polyphagous shot hole borer, which was detected too recently.) 107 species are considered by experts to be having either major or severe impacts on biodiversity and/or human wellbeing. Alien species richness is highest in the savanna, grassland, Indian Ocean coastal belt and fynbos biomes, lower in the more arid Karoo and desert biomes. South Africans are particularly focused on the reductions in surface water resulting from plant invasions. The decades-old “Working for Water” program has two goals: providing employment and development opportunities to disadvantaged individuals in rural areas, and managing invasive alien plants.

The Status of Biological Invasions and Their Management in South Africa is available here.

Posted by Faith Campbell

Worldwide – and U.S. – Proliferation of Phytophthora via the Nursery Trade – an Update

Phytophthora cinnanomi killing Ione manzanita in California; photo from Swiecki and Garbelotto, Distribution of Phytophthora cinnamomi within the range of Ione manzanita (Arctostaphylos myrtifolia). Agreement between the California Department of Fish and Game and University of California

Phytophthora species are plant pathogens in the oomycote group (water molds, closely related to brown algae). More than 160 species have been described; new species are continually being isolated. Many Phytophthora species are deadly to naïve hosts; examples in the United States include sudden oak death, Port-Orford cedar root disease, disease on chestnuts and oaks.

Forests in Europe – especially the United Kingdom – and Australia are also suffering high levels of mortality associated with one or more Phytophthora species.

In recent years, several studies have documented the role of nurseries in spreading non-native Phytophthora species. Two strains of P. ramorum are widespread in European nurseries and in tree plantations and wild heathlands of southwest England, Wales, parts of Scotland, and Ireland. (See here and here.)

In April 2016 I blogged about the situation in Europe described by Jung et al. 2015 (see references at the end of the blog). Jung et al. concluded that diseases caused by Phytophthora pose a substantial threat to both planted landscapes and forest ecosystems across Europe. They found 56 Phytophthora taxa in 66% of 2,525 forest and landscape planting sites that were probably introduced to those sites via nursery plantings.

Barber et al. 2013 reported nine species of Phytophthora associated with a wide variety of host species in urban streetscapes, parks, gardens, and remnant native vegetation in urban settings in Western Australia. Phytophthora spp were recovered from 30% of sampled sites.

A new summary confirms that the threat is similar in North America. In British Columbia, Dale et al. (2017) found more than two times as many Phytophthora species were detected in soil and water samples in urban areas (23) than in natural areas (11). Urban samples also showed a much higher diversity of Phytophthora per site than natural environments. These Phytophthora species had been introduced initially into urban areas and had subsequently spread into native vegetation, particularly in areas near developed sites (wildland-urban interface areas).

Swiecki et al 2018 cite several sources and their own studies to show that the large and increasingly diverse contingent of introduced Phytophthora species pose an increasingly important threat to both urban forests and surrounding native forests and plant communities in California. It is clear that shrubs and herbaceous plants as well as trees are also at risk. These scientists have repeatedly found multiple non-native Phytophthora species at individual sites in northern and southern California sites where nursery stock had been planted. Sampling in 2014 identified about 60 different Phytophthora taxa in restoration planting sites and native plant nurseries. The sampled restoration plantings were mostly located in urban riparian corridors and peri-urban parks, open spaces, or protected watersheds.

I first discussed this issue in a blog in July 2016.

Swiecki et al (2018) have also found that Phytophthora species persist in drier ecosystems. When conditions are too dry for sporangium production, Phytophthora hyphae produce resistant survival structures that can tolerate drying and persist in dead root fragments or soil. In the presence of appropriate stimuli, e.g., moisture and root exudates, resistant structures germinate to produce sporangia or hyphae, leading to new infections. Even relatively short wet periods associated with rain or irrigation can be sufficient to stimulate zoospore release. Swiecki et al (2018) list examples of numerous Phytophthora infestations that developed in dry sites, such as dry foothills of the Sierra Nevada in Amador County, and the Oakland Hills of Alameda & Contra Costa County. Swiecki et al. (2018) also note that P. cinnamomi has persisted in Australian forests in the absence of known primary hosts.

Phytophthora infections can also persist for decades in soil. In California, Swiecki et al. (2018) mention several examples:

Residual cinnamomi inoculum killed young sprouts of susceptible manzanitas (Arctostaphylos myrtifolia and A. viscida) planted on sites that were infected many years earlier.
A street planting of cork oaks (Quercus suber) apparently died due to Phytophthora root rot that had occurred 21 years earlier.
Both cinnamomi and P. cactorum were recovered from roots and soil beneath affected trees at least 60 years after the site had been a municipal woody plant nursery and adjacent residence.
A 7-acre area of native vegetation showing decline & mortality of multiple plant species was infested with multiple Phytophthora spp, including cactorum, P. cambivora, P. crassamura, P. ‘kelmania’ & P. syringae. The site was apparently infected 22 years earlier during a planting of a habitat restoration project using Ceanothus nursery stock. Subsequent spread was primarily downhill from the planting sites, facilitated by water flow, with additional spread along and near trails.

The Risk from the Nursery Trade

While Phytophthora-infested soil and plant debris can be transported on tools, vehicles, and shoes, or moved in large quantities when infested soil is excavated, graded, or imported, the principal threat is the nursery trade.

Jung et al. (2015) state that widespread contamination of nursery stock was the primary means by which these pathogens were introduced and spread in Europe. They found 49 Phytophthora taxa in 670 European nurseries. Phytophthora species were recovered from more than 90% of the sampled nurseries.
Swiecki et al. (2018) say that most of the common Phytophthora species detected in California are distributed globally, moved about with live plants or other infested materials. None is native to California.
Swiecki et al. (2018) cite studies reporting that thirteen species of Phytophthora were found in a survey for leaf spots in California nurseries in 2005 and 2006. Sampling of plants in or originating from Calif native plant nurseries alone has yielded about 60 Phytophthora At least eight species of Phytophthora were found in shipments of symptomatic and asymptomatic plants sent from west coast nurseries to Maryland. Parke et al. (2014) identified 28 Phytophthora taxa in four Oregon nurseries.
Not all infections are on the West Coast. Swiecki et al. (2081) reports that a survey in Minnesota nurseries of plants with symptoms – primarily on aboveground plant parts – found eleven species of Phytophthora.

Are scientists in other parts of the country looking for Phytophthora? I see no reason to think the situation in California is unique.

The damage caused by Phytophthora infections can be significant. In California and Oregon, sudden oak death, and Port-Orford cedar root disease, have killed well over a million trees and disrupted the ecosystems of which they are a part. There are multiple locations in Northern California where introduced Phytophthora species, especially P. cinnamomi and P. cambivora, have caused localized to extensive decline and mortality in native forests and shrublands.

Phytophthora dieback has infected more than one million hectares in Western Australia. More than 40% of the native plant species of the region are vulnerable to the causal agent, P. cinnamomi.

Phytophthora dieback in Western Australia

Dieback in native forest in Western Australia; photo copyright Western Australian Department of Parks and Wildlife

In the United Kingdom, several Phytophthora species are causing widespread mortality of native shrubs and trees and commercial plantings.

In nearly all the studies, scientists have detected previously unknown pathogen-host relationships.

The threat from spreading pathogens with wide host ranges is not limited to the genus Phytophthora. The fungus Fusarium euwallacea associated with the Kuroshio and polyphagous shot hole borers is known to kill at least 18 species of native plants in California and additional species in South Africa. The laurel wilt fungus kills many trees and shrubs in the Lauraceae family. ‘Ohi‘a or myrtle rust kills several shrubs native to Hawai`i and threatens a wide range of plants in the Myrtaceae family in Australia and New Zealand. Some insects also have wide host ranges, including the Kuroshio and polyphagous shot hole borers; and Asian longhorned and citrus longhorned beetles.

When are national and international phytosanitary agencies going to adopt policies and programs that are effective in preventing the continued spread of these highly damaging tree-killing pests? At the national level, APHIS needs to aggressively use two authorities to curtail importation of plant taxa from countries of origin which present a risk of transporting additional species of pathogens:

NAPPRA, which allows APHIS to prohibit risky imports until it has conducted a pest risk analysis.
Programs under the revised “Q-37” regulations allowing APHIS to work with exporting countries’ phytosanitary officials to implement integrated pest management strategies to ensure that plants are pathogen-free before they are exported.

I have blogged about both programs before – NAPPRA here; the Q-37 regulation strengthening here.

At the international level, the members of the International Plant Protection Convention (IPPC) must recognize the failure of the international phytosanitary system and explore ways to strengthen it. See my numerous blogs on this topic (beyond those linked to here!) by visiting www.cisp.us or www.nivemnic.us and searching under the category “forest pathogens”.

Posted by Faith Campbell

SOURCES

Jung, T. et al. 2015 “Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora disease” Forest Pathology. November 2015; available from Resource Gate

Swiecki, T.J., E.A. Bernhardt, and S.J. Frankel. 2018. Phytophthora root disease and the need for clean nursery stock in urban forests: Part 1 Phytophthora invasions in the urban forest & beyond. Western Arborist Fall 2018

Apparently can’t access current (2018) issues of “Western Arborist” on web unless subscribe

Scientists Document Alarming Declines in Insects

Luquillo Forest in Puerto Rico

While I usually blog about insects (and plant pathogens) that have invaded new ecosystems and are killing native plant species, I am aware that insects are numerous and vitally important components of the ecosystems in which they evolved. I join others in noting with concern evidence that insect populations in wide-apart areas have declined at very high rates. Insects appear to be affected by the Sixth Extinction Event (concept described here and here) as much as or possibly more than various vertebrate and plant taxonomic groups.

The Zoological Society of London and World Wildlife Fund published this week the 2016 version of the Living Planet report. Based on an analysis of 3,700 vertebrate species (birds, fish, mammals, amphibians and reptiles), the authors concluded that global wildlife populations have fallen by 58% since 1970 (Morelle; see references at the end of the blog).

Dirzo et al. in 2014 provided a very interesting discussion of the impacts of species’ declines in numbers and local extinctions – short of complete extinction. They asserted that “declines in numbers of individuals in local populations and changes in the composition of species in a community will generally cause greater impacts on ecosystem function than global extinctions. Dirzo et al. noted the importance of invertebrates, especially insects, in ecosystem functioning. They stated that the smaller fauna – including insects – “arguably are more functionally important” than charismatic megafauna and called for improved monitoring and study of such taxa, particularly invertebrates,

In their study, Dirzo et al. estimated that, since 1970, Lepidoptera – an order containing many important pollinators – had declined 35% in abundance globally over 40 years. Declines of other insect orders were considerably more. One study they cited found an overall 45% decline for all invertebrate populations over 35 years. More recent studies find decline rates that considerably exceed the estimated decline of 58% in global abundance of wild vertebrates over a 42-year period (Morelle; Hallmann et al.)

A year ago, Hallmann et al. reported a 76% decline in the biomass of flying insects over a 27-year period in Germany. There were seasonal variations; in midsummer, when insect biomass is highest, the decline was 82%. The study was carried out in nature protection areas – that is, places set aside and protected to conserve biological diversity. Hallmann et al. predict cascading effects on food webs and jeopardy to ecosystem services, including pollination, herbivory and breakdown of detritus, nutrient cycling and providing a food source for higher trophic levels such as birds, mammals and amphibians.

Hallmann et al. said that changes in weather, land use, and habitat characteristics could not explain this overall decline. Declines occurred in both nutrient-poor habitat types (e.g., heathlands, sandy grasslands, and dunes) and nutrient-rich habitats (grasslands, margins and wasteland), as well as in pioneer and shrub communities.

Another of the few studies looking at insects broadly, a study of flying insect biomass in the United Kingdom, found a biomass decline at only one of the four sites. Hallmann et al. note that the British researchers used considerably different sampling methods that targetted primarily high-flying insects (and caught mostly members of one fly family) whereas their own Malaise traps caught insects flying close to the ground and a much wider diversity of taxa.

Taxon-specific studies have also found severe declines in insect populations.

Hallmann et al. concluded that the scale of decline in insect biomass – throughout the growing season, and irrespective of habitat type or landscape configuration – suggest that large-scale factors must be involved. As noted, their data did not support either landscape changes or climate change as explanatory factors – although they admit that they did not exhaustively analyze the full range of climatic variables that could potentially impact insect biomass. Hallmann et al. did think that agricultural intensification (e.g. pesticide usage, year-round tillage, increased use of fertilizers and frequency of agronomic measures) was a plausible cause of insect biomass decline given the reserves’ limited size in typically fragmented western-European landscapes. The noted that the protected areas might serve as insect sources which might be counterbalanced by the surrounding agricultural fields, which might act as sinks or ecological traps.

While Hallman et al. did not specify the types of pesticides being used by the German farmers operating near their study areas, in recent years there has been growing concern about widespread use of neonicotenoids, which appear to pose a threat to bees and possibly other insects. Three sources of information are the European Food Safety Agency; Xerxes Society; and petition pertaining to regulation of seeds treated by neonicotenoids submitted by the Center for Food Safety.

This month, Bradford Lister and Andrés García published a study that compared numbers of the insects and insectivores (birds, frogs, lizards) in Puerto Rico’s tropical rainforest in 2012 to results of Lister’s studies there in 1976 and 1977. Overall arthropod biomass in Puerto Rico’s Luquillo rainforest fell 10 to 60 times since 1970s (Lister and Garcia). Numbers of insects in the vegetation collected by sweep nets decreased to a fourth or an eighth of what they had been. The catch rate of ground-dwelling arthropods caught in sticky traps fell 60-fold (Guarino).

Lister and Garcia attribute the crash in arthropod numbers to climate change, especially rising maximum temperatures. They note that over the same 40-year period, the average high temperature in the rainforest increased by 4 degrees Fahrenheit (2^oC). Lister and Garcia cite several studies indicating that tropical invertebrates are adapted to a narrow band of temperatures.

Lister and Garcia also measured declines among insect-feeding vertebrates. The biomass of anole lizards dropped by more than 30%. Some anole species disappeared from the interior forest (Guarino). Declines in number of coqui frogs (Eleutherodactylus spp) began in the 1970s. Currently, three of 16 species are extinct, and the remaining 13 species are classified in some category of endangered or threatened. Disease caused by the fungus Batrachochytrium dendrobatidis is not a factor at the elevations where study done.

Citing data from other researchers, Lister and Garcia report that numbers of insectivorous birds captured in mist nets fell 53% between 1990 and 2005.

Lister and Garcia sought to explain why there were simultaneous, long-term declines in arthropods, lizards, frogs, and birds over the past four decades in the relatively undisturbed rainforests of northeastern Puerto Rico. They concluded that climate warming has been a major factor driving reductions in arthropod abundance, and that these declines have in turn precipitated decreases in forest insectivores in a classic bottom-up cascade.

As supporting evidence, Lister and Garcia cite

(1) Declines across varied species and communities that occurred in parallel with rising temperatures.

(2) Simultaneous declines of all arthropod taxa in their own and others’ studies – pointing to an overriding environmental factor that has had ubiquitous, adverse effects on forest arthropods regardless of taxonomic affiliation, stratum occupied, or type of niche exploited.

(3) Declines in arthropod abundance that occurred despite major decreases in their predators – and, presumably, reduced predatory pressure..

Lister and Garcia note that there have been almost no significant human perturbations in the Luquillo forest since the 1930s, and that pesticide use in Puerto Rico fell nearly 80% over the past 40 years with the decrease in agricultural activity on the island. Some of the insect trend data came from studies carried out in the Luquillo Long Term Ecological Study site.

Lister and Garcia say that major weather perturbations have also had an impact. Over the 36-year time span, there have been five major hurricanes and eight severe droughts. They note that the island’s vegetation regenerated rapidly after hurricanes Hugo and Maria; insect populations regenerated rapidly after Hurricane Georges. La Niña episodes led to an immediate increase in the abundance of canopy invertebrates, whereas El Niño episodes caused declines.

Of course, some insects are under threat from loss of their primary food plants to invasive species. I note particularly the Palamedes swallowtail butterfly (Papilio palamedes), which depends on redbay and swamp bay, and an estimated 21 species of North American butterflies and moths believed to specialists or largely dependent on ash.

Palamedes swallowtail; photo by Vincent P. Lucas

In some cases, e.g., hemlock woolly adelgid and Asian longhorned beetle, neonicotenoids, specifically imidacloprid, is an essential tool to controlling a tree-killing invasive insect.

SOURCES

Dirzo, R., H.S. Young, M. Galetti, G. Ceballos, N.J. B. Isaac, B. Collen. 2014. Defaunation in the Anthropocene. Science 345, 401

Guarino, B. 2018. ‘Hyperalarming’ study shows massive insect loss. 2018. The Washington Post October 15 2018

Hallmann CA, Sorg M, Jongejans E, Siepel H, Hofland N, Schwan H, et al. 2017. More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLoS ONE 12 (10): e0185809. https://doi.org/10.1371/journal. pone.0185809

Lister, B.C. and A. Garcia. 2018. Climate-driven declines in arthropod abundance restructure a rainforest food web. Proceedings of the National Academy of Sciences. http://www.pnas.org/content/early/2018/10/09/1722477115

Morelle, R. Science Correspondent, BBC News. 2018. World wildlife ‘falls by 58% in 40 years’ https://www.bbc.com/news/science-environment-37775622

South Africa’s unique flora put at risk by polyphagous shot hole borer

The polyphagous shothole borer (PSHB) and its fungal symbiont Fusarium euwallaceae are killing trees in South Africa as well as in California.

Erythrina humeana in the Manie van der Schijff Botanical Garden, Pretoria

The pest complex’s presence was detected in August 2017 through an international sentinel tree program – the first detection of a tree pest under the program. Under the ‘sentinel plantings’ program, staff at botanical gardens and arboreta monitor their holdings – often exotic species growing outside of their natural range – and alert program partners when they detect damage caused by insects or pathogen not previously known to pose a risk. The International Plant Sentinel Network (IPSN) was launched in 2013. Botanical gardens and arboreta in South Africa joined the international effort in 2016 (Paap et al. 2918 – see list of sources at the end of this blog).

PSHB-caused tree mortality was initially detected in the KwaZulu-Natal National Botanical Gardens in Pietermaritzburg in August 2017. Affected trees were London Plane (Platanus x acerifolia) (Paap et al. 2018).

A beetle collected in 2012 in Durban, 50 km away from Pietermaritzburg, has now been determined to belong to the Euwallacea fornicatus species complex – indicating that the invasive insect and fungal species have been established in South Africa for several years (Paap et al. 2018). [Interestingly, 2012 is also the year that Dr. Akif Eskalen detected PSHB in a backyard avocado in southern California – setting off the detection, research, and slow-the-spread efforts now under way there.]

2018-10-01 PSHB - South Africa

locations of PSHB detections in South Africa; map from http://polyphagous-shot-hole-borer.co.za/

South African authorities were immediately concerned because the beetle-fungus complex attacks such a broad range of trees (species in 58 plant families). Hosts include several species native to southern Africa – including cabbage tree (Cussonia spicata), common calpurnia (Calpurnia aurea), monkey plum (Diospyros lycioides), two species of coraltree (Erythrina humeana and E. lysistemon), huilboerboon (Schotia brachypetala), honey flower (Melianthus major), two alders (Cunonia capensis and Nuxia floribunda), and red orchid bush (Bauhinia galpinii). Also at risk are several commercial crop trees such as avocado (Persea americana), macadamia nut (Macadamia integrifolia), pecan (Carya illinoinensis), peach (Prunus persica), orange (Citrus sinensis) and grapevine (Vitis vinifera) and several ornamentals, including maple, holly, wisteria, oak and Camellia (Paap et al. 2018).

South Africa is home to a highly unique flora. Indeed, the “Cape Floral Kingdom” is the smallest of the six floral regions on Earth. For more about South Africa’s botanical importance, go here or here.

Rapid spread of the beetle-fungus complex appears likely because one of the most important reproductive hosts, castor bean (Ricinus communis) is a widespread woody weed in the KwaZulu-Natal region (Paap et al. 2018).

By July 2018, it was clear that PSHB was established in several parts of the country (see map). In George — a city along the southern coast, due east of Capetown, the beetle and fungus are affecting a wide range of indigenous and exotic trees in the botanical garden and the region‚ including box elder‚ Chinese and Japanese maple‚ oak‚ plane trees‚ Kapok trees‚ paper bark acacia‚ wild plum‚ dwarf corral and common corral (Chambers 2018).

In Johannesburg, a concerned citizen tracking the pest complex’ spread thinks that the beetle-fungus combination has already infested well over 100,000 of Johannesburg’s trees and is on track to damage or kill millions more (there are an estimated 6 – 10 million trees in Johannesburg, nearly all exotic) (Weltz 2018).

SOURCES

Chambers, D. “A 2mm beetle is laying waste to George’s trees” Sunday Times. 30 May 2018 https://www.timeslive.co.za/news/sci-tech/2018-05-30-a-2mm-beetle-is-laying-waste-to-georges-trees/

Johannesburg Urban Forest Alliance. The Shot Hole Borer Beetle is destroying our Urban Forest http://www.jufa.org.za/pshb.html

Paap, T., Z.W. de Beer, D. Migliorini, W.J. Nel, M.J. Wingfield. 2018. Australasian Plant Pathology https://doi.org/10.1007/s13313-018-0545-0 https://link.springer.com/article/10.1007/s13313-018-0545-0

Weltz, A. Beetle Mania The Nasty Insect that is Killing the Trees of Johannesburg. Yale Environment 360; Published at the Yale School of Forestry and Environmental Studies. https://e360.yale.edu/features/beetle-mania-the-nasty-insect-that-is-killing-the-trees-of-johannesburg

Is EAB deregulation necessary? Is it helpful? What is at risk?

EAB risk to Oregon & Washington

USDA APHIS has formally proposed to end its regulatory program aimed at slowing the spread of the emerald ash borer (EAB) within the United States. APHIS proposes to rely on biological control to reduce impacts and – possibly – slow EAB’s spread. The proposal and accompanying “regulatory flexibility analysis” are posted here.

Public comments on this proposed change are due 19 November, 2018.

I will blog more fully about this issue in coming weeks. At present, I am on the fence regarding this change.

On the one hand, I recognize that APHIS has spent considerable effort and resources over 16 years trying to prevent spread of EAB – with less success than most would consider satisfactory. (EAB is known to be in 31 states and the District of Columbia now). While APHIS received tens of millions of dollars in emergency funding in the beginning, in recent years funding has shrunk. Over the past couple of years, APHIS has spent $6 – $7 million on EAB out of a total of about $54 million for addressing “tree and wood pests.” (See my blogs on appropriations by visiting www.cisp.us, scrolling down to “topics,” then scrolling down to “funding”). Funding has not risen to reflect the rising number of introduced pests. Presumably partly in response, APHIS has avoided initiating programs targetting additional tree-killing pests. For example, see my blogs on the shot hole borers in southern California and the velvet longhorned beetle by visiting www.cisp.us, scrolling down to “categories,” then scrolling down to “forest pest insects”. I see a strong need for new programs on new pests and money now allocated to EAB might help fund such programs.

On the other hand, APHIS says EAB currently occupies a quarter of the range of ash trees in the U.S. Abandoning slow-the-spread efforts put at risk trees occupying three quarters of the range of the genus in the country. (See APHIS’ map of infested areas here.) Additional ashes in Canada and Mexico are also at risk. Mexico is home to 13 species of ash – and the most likely pathway by which they will be put at risk to EAB is by spread from the U.S. However, APHIS makes no mention of these species’ presence nor USDA’s role in determining their fate.

I am concerned by the absence of information on several key aspects of the proposal.

APHIS makes no attempt to analyze the costs to states, municipalities, homeowners, etc. if EAB spreads to parts of the country where it is not yet established – primarily the West coast. As a result, the “economic analysis” covers only the reduced costs to entities within the quarantined areas which would be freed from requirements of compliance agreements to which they are subject under the current regulations. APHIS estimates that the more than 800 sawmills, logging/lumber producers, firewood producers, and pallet manufacturers now operating under compliance agreements would save between $9.8 M and $27.8 million annually. This appears to be a significant benefit – but it loses any meaning absent any estimate of the costs that will be absorbed by governments and private entities now outside the EAB-infested area.

ash tree killed by EAB; Ann Arbor, MI; courtesy of former mayor of Ann Arbor, MI John Hieftje

APHIS does not discuss how it would reallocate the $6 – 7 million it spends on EAB. Would it all go to EAB biocontrol? Would some be allocated to other tree-killing pests that APHIS currently ignores?

APHIS provides no analysis of the efficacy of biocontrol in controlling EAB. It does not even summarize studies that have addressed past and current releases of EAB-specific biocontrol agents. (I will report on my reading of biocontrol studies in a future blog.)

APHIS says efforts are under way to develop programs to reduce the risk of pest spread via firewood movement. APHIS does not explain what those efforts are or why they are likely to be more effective than efforts undertaken in response to recommendations from the Firewood Task Force issued in 2010.

APHIS makes no attempt to analyze environmental impacts.

champion green ash in Michigan killed by EAB

APHIS says nothing about possibly supporting efforts to breed ash trees resistant to EAB.

I welcome your input on these issues.

I will inform you of my evolving thinking, information obtained in efforts to fill in these gaps, etc. in future blogs.

Posted by Faith Campbell

Challenges to Phytosanitary Programs are International, Not Just in the U.S. How Should We Join Efforts to Defend Them?

dead ash killed by emerald ash borer; photo by Dan Herms, The Ohio State University; courtesy of Bugwood.com

I have blogged often about the funding crisis hampering APHIS’ efforts to protect our forests from damaging insects and pathogens (visit www.cisp.us, scroll down to “categories”, then scroll down to “funding”). Apparent results of this funding crisis include APHIS’ failure to adopt official programs to address several tree-killing pests (e.g., polyphagous and Kuroshio shot hole borers, goldspotted oak borer, spotted lanternfly …) and its proposal this month to end the regulatory program intended to slow the spread of the emerald ash borer (available here.) (All these tree-killing pests are described here.)

The lack of adequate resources plagues phytosanitary programs in many countries as well as at the international and regional level. As we know, the threat of introduction and spread of plant pests is growing as a result of increasing trade volume and transportation speed; increasing variety of goods being traded; and the use of containers. All countries and international bodies should be expanding efforts to address this threat, not cutting back.

Assuming you agree with me that preventing and responding to damaging plant pests is important – a task which falls within the jurisdiction of phytosanitary institutions – what more can we do to raise decision-makers’ and opinion leaders’ understanding and support? Should we join phytosanitary officials’ efforts – e.g., the International Year of Plant Health – or act separately?

How do we encourage greater engagement by such entities as professional and scientific associations, the wood products industry, state departments of agriculture, state phytosanitary officials, state forestry officials, forest landowners, environmental organizations and their funders, urban tree advocacy and support organizations. (The Entomological Society of America has engaged on invasive species although it remains unclear to me whether ESA will advocate for stronger policies and higher funding levels.)

There is one group making serious, multi-year efforts to respond. Here, I describe efforts by the International Plant Protection Convention’s (IPPC) governing body, the Commission on Phytosanitary Measures. The Commission has recognized the crisis and is attempting to reverse the situation through a coordinated strategy. I invite you to consider how we all might take part in, and support, its efforts.

Efforts of the IPPC Commission on Phytosanitary Measures

The Commission’s goal is to ensure that strong and effective phytosanitary programs “become a national and global priority that justifies and receives appropriate and sustainable support.” It seeks to achieve this by convincing decision-makers that protecting plant health from pest threats is an essential component of efforts to meet other, more broadly accepted goals, specifically the United Nations’ 2030 Sustainable Development Agenda and the Food and Agriculture Organization’s (FAO) related goals (described here).

The IPPC Commission also sees that, to succeed, it must more effectively support member countries in improving their programs to curtail pests’ spread and impacts. IPPC plans to streamline operations and integrate more closely with other FAO work in order to save money.

The following are among Commission efforts, although all are hampered by the lack of funding:

Working with member countries, the Commission has persuaded the United Nations to declare 2020 the International Year of Plant Health. (I blogged about this campaign in December 2016.
Describing links between plant health and other policy goals. The Commission is mid-way through a multi-year program. One outcome has been presentations to member states’ phytosanitary officials attending the Commission’s annual meetings, each focusing on one specific aspect. In 2018, presentations focus on links between plant health and environmental protection (presentations from April 2018 are available here). (Did you know 2018 was the year of plant health and the environment? I didn’t!) In 2016, the topic was plant health’s link to food security; in 2017, plant health and trade facilitation; in 2019, capacity development for ensuring plant health.)
Adopting a Communications Strategy. It has four broad objectives (available here).
increase global awareness of the importance of the IPPC and of the vital importance to the world of protecting plants from pests;
highlight the IPPC’s role as the sole international plant health standard setting organization aimed at improving safety of trade of plants and plant products and improving market access;
improve implementation of IPPC’s international standards (ISPMs); and
support the activities of the IPPC Resource Mobilization program.
Ramping up efforts to support implementation of its international standards. Since this 2014 decision, the Commission has conducted some pilot projects, restructured the Secretariat, and formed the Implementation and Capacity Development Committee. (I have blogged frequently about issues undermining one of those standards, the one on wood packaging material – ISPM#15. Visit www.cisp.us, scroll down to “categories”, then scroll down to “wood packaging”.)

Framework 2020-2030: the IPPC Strategic Plan

The IPPC is now finalizing its strategic plan (Framework 2020-2030), which is available here. APHIS circulated this plan in July for comment; I admit did not take the opportunity to comment because I could think of nothing to add. But now I want to link the international and domestic U.S. funding crises.

The plan describes how plant pests threaten

food production at a time rising human population and demand;
sustainable environments and ecosystem services at a time when recognition is growing of their importance for managing climate change and meeting food production goals;
free trade and associated economic development;

The plan notes that interactions between climate change and pests’ geographic ranges and impacts complicate efforts to address both threats. Also, it outlines the need for, and barriers hindering, collaborative research on plant pest. It suggests creation of an international network of diagnostic laboratories to support reliable and timely pest identifications.

The plan states several times that the IPPC is “the global international treaty for protecting plant resources (including forests, aquatic plants, non-cultivated plants and biodiversity) from plant pests …” (emphasis added). The Commission is attempting to improve its efforts to protect the environment through expanding its collaboration with the Convention on Biological Diversity, Global Environmental Facility and the Green Climate Fund. Much of the attention to environmental concerns is focused on interactions with climate change, followed by concerns about pesticide use. Indeed, the strategic plan states that “Political weight and subsequent funding for phytosanitary needs on national, regional and international level will only be available when phytosanitary issues are recognized as an important component of the climate change debate.”

The Plan describes other ways that the Commission and regional plant protection organizations might help countries overcome the major problems arising from their lack of capacity and resources. Another area of hoped-for activity is promoting collaborative research. All these proposals depend on finding funding.

However, the Strategic Plan does not reveal the extent to which its 2013 Communications Strategy has been implemented. Nor does it reveal the extent to which the effort to improve ISPM implementation has resulted in concrete progress.

Posted by Faith Campbell