Those of us striving to increase action! to curb bioinvasion have had a hard time demonstrating socio-economic costs sufficiently compelling to prompt adoption of more effective policies. However, see
Donovan, et al. 2013. The Relationship Between Trees and Human Health. American Journal of Preventive Medicine. Volume 44 Issue 2.
Fantle-Lepczyk, et al. 2022. Economic costs of biological invasions in the United States. Science of the Total Environment 806 (2022) 151318
Now, two new papers show how high the costs can be under some circumstances.
Eyal G. Frank compared the rate of infant mortalityin counties across the U.S. where insectivorous bats had been severely reduced by whitenose syndrome to that in counties where bat populations were not affected. He found that “internal” infant mortality – defined as deaths not caused by accidents or homicides — rose, on average, 7.9%. An estimated additional 1,334 infants died. [A related finding not directly pertinent to this blog’s purpose: Frank notes that real-world use levels of insecticides have a detrimental impact on health, even when used within regulatory limits.]
Whitenose syndrome (WNS) is caused by Pseudogymnoascus destructans, a fungus native to Europe. It was introduced to North America around the beginning of the 21st Century. It has spread quickly since its initial detection in 2006. By 2024, populations of 12 of ~ 50 insectivorous bat species in the US have been negatively affected. The fungus has caused an estimated decline of more than 90% in bat populations monitored in hibernating caves (Larson, Engst, and Noack 2024).
This population crash is devastating, especially where pest control is supplied by bats. Individual bats are voracious predators. But, for pest control to succeed, the total population must be high. .
Frank compiled information at the county level on:
the spread of white nose syndrome to new counties;
rates of pesticide application, presuming that higher rates reflected increased insect presence on crops; and
infant mortality rates.
Larson, Engst, and Noack (2024) call Frank’s findings on infant mortality “shockingly large”. The increase in insecticide application rates was just 2.7 kg/km2. These findings show that technological substitutes for suppressed biological services can markedly and adversely affect human well-being.
Both Frank and Larson, Engst, and Noack emphasize the value in demonstrating that declines in biological diversity do have repercussions for human well-being. They call for more expansive and intensive monitoring of biodiversity trends, especially among non-charismatic taxa such as insects. Furthermore, there should be more multidisciplinary studies that integrate social, natural, and health datasets and research methods to distill information of policy relevance. The Science authors’ expectation is that quantifying these relationships will guide better decisions about conservation policies.
All the authors devote considerable attention to the difficulty in establishing these links because scientists cannot manipulate large-scale ecosystems to conduct experiments. They recommend taking advantage of natural experiments – such as tracking the spread of a newly introduced disease that kills large proportions of a taxon that provides demonstrated ecosystem services. Frank studied the loss of insectivorous bats. Larson, Engst, and Noack (2024) mention an earlier study of the collapse of amphibian populations in Central America caused by the fungal pathogen Batrachochytrium dendrobatidis. One result in this case was an increase in the incidence of malaria.
Frank and Larson, Engst, and Noack clearly hope that this approach will promote stronger and more targetted biodiversity conservation policies and programs. I hope they are right! But did enough Americans hear about these results? I heard a report on “BBC America” radio. I searched and found a print report published by Vox – which connected me to Science. How do we expand media coverage of this type of information?
SOURCES
Frank, E.G. 2024. The economic impacts of ecosystem disruptions: Costs from substituting biological pest control. Science. 6 Sep 2024 Vol 385, Issue 6713 DOI: 10.1126/science.adg0344
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 these pests to enter and spread – and that do not promote effective restoration strategies – review the Fading Forests report at https://treeimprovement.tennessee.edu/
sooty bark disease; photo by Vincet Gaucet via Bugwood
Recently, plant pathologists have paid more attention to pathogens — native to eastern North America — now killing trees on the West Coast. Years ago, the likelihood of such “domestic invaders” was hotly debated. However, these new detections provide examples of native micro-organisms that are apparently benign in the ecosystems in which they evolved, but that cause disease when moved to relatively nearby — but naïve — environments. I would argue that it is the absence of co-evolution of pathogen and host, not distance, that matters. In both cases, environmental stress on the trees appears to play a significant role. Such stress is expected to increase as the climate changes.
[In the past, these issues arose re: goldspotted oak borer – introduced to California from Arizona; and thousand cankers disease – introduced from Arizona to Western states and now to the East.]
Little is known about these diseases. So far, scientists have examined the pathogens’ impacts more thoroughly on plantings that are introduced to the location, so already outside of the forest biomes in which they evolved. Less attention has been paid to hosts native to the regions newly affected. I find this disturbing because I am most concerned about the possible impact to native ecosystems.
I will describe two such diseases. Both attack native tree species, not just the exotic trees described in research. Both were first detected in the Pacific Coast states in the late 1960s – i.e., more than 50 years ago. Why are they becoming prominent now – is it changes in the climate? Evolution? Just slow adaptation?
Example One – Sooty Bark Disease
Sooty-bark disease (Cryptostroma corticale) of maples (Acer spp.) is native to the Great Lakes region, where it causes no problems. However, it has been introduced to the West Coast, where all sources agree that the disease kills trees stressed by heat and drought. These stresses are expected to increase as the climate changes. The disease is also a serious threat to human health. The fungus’ spores can cause serious pulmonary disease in humans.
Sooty bark disease was detected in Pullman, Washington, near the Idaho border, in 1968. Now it is more widespread: it was detected in the Seattle area as of 2020 and the Sacramento area of California in 2019 [Curtis Ewing pers. comm.]. Sooty-bark disease has also spread to at least ten countries in Europe, ranging from the United Kingdom to Italy and Bulgaria.
Sources in Washington say hosts include several non-native species widely planted in the area – sycamore maples (Acer pseudoplatanus) [Chastagner], Norway maples (Acer platanoides), Japanese maple (A. palmatum), and horsechestnut (Aesculus hippocastanum) [Chastagner and Washington State University]. More troubling is the fact that several native tree species are also hosts. Big leaf maple (A. macrophyllum), and Pacific dogwood (Cornus nuttallii) are among the most significant. [Big leaf maple is a large hardwood tree in a region dominated by conifers. Pacific dogwood has already been decimated by the introduced disease dogwood anthracnose.] Sources in California add two other maples, these native to eastern North America, red (A. rubrum) and silver (A. saccharinum) maples.
bigleaf maples in Olympic National Park; NPS photo
The fungus initiates infection in a tree’s small branches, then spreads into the heartwood and both up and down the tree. It might also invade pruning wounds. The fungus grows more rapidly at higher temperatures. It is also facilitated by drought stress. When the fungus grows out to the bark, it causes the bark to blister; it then forms spore-forming structures. The spores are dispersed by wind. (Chastagner)
Washington State University’s Ornamental Plant Pathology division has called for more research on all aspects of the disease in trees:
Distribution and spread of the disease;
Plant species susceptibility and host range;
Diagnostic methods and molecular approaches to improve diagnostic efficiency and capacity;
Pathogen life history and genetic diversity;
Factors that affect disease development and vulnerability (site, stress, age of host, etc.);
Potential of human mediated dispersal and vectors such as pruning tools;
Best management practices and worker protection.
So far, little has been done. Scientists in the Pacific Northwest have received a small amount of funding from the USDA Forest Service Forest Health Protection Emerging Pests program link + blog on appropriations to increase diagnostic services and to surveys trees elsewhere in the Puget Sound region.
Example Two – Bacterial Pathogen on Oaks
drippy blight disease on northern red oak; photo by Rachel Sitz, USDA Forest Service; via Bugwood
There is always concern about threats to oaks (Genus Quercus) because of their ecological, economic, and social importance. As Kozhar et al. point out, this genus is one of the most important groups of trees in many regions of the Northern Hemisphere. In North America specifically, oak forests compose a significant part of many forest ecosystems, especially in the East. California has 20 native species, Colorado has one. In addition, oaks are also often planted as shade trees in urban environments, which has resulted in movement of oak species to new geographic areas. There where they experience different environmental conditions, they might find new pests or alert us to the effects of climate change.
The bacterial oak pathogen Lonsdalea quercina is indigenous to the native range of northern red oak (Quercus rubra) in eastern North America. There, it does not cause disease in its co-evolved host. However, it has recently caused two outbreaks in the West – in California and Colorado. In the latter, trees themselves can die; in the former, acorns are damaged, threatening forest regeneration. Other Lonsdalea species have caused similar tree diseases in Europe.
California
In California, the bacterium has been present since at least 1967. It infects acorns of native oaks, including coast live oak (Q. agrifolia), Q. parvula (presumably the mainland subspecies, also named Q. p. var. shrevei),and interior live oak (Q. wislizeni). The Morton Arboretum link says Q. parvula (presumably – again – the mainland subspecies) is currently threatened by sudden oak death (SOD). Coast live oak has also been highly affected by sudden oak death (SOD), DMF but it is not considered to be threatened. I expect – but sources don’t say – that the bacterium is affecting these species’ reproduction.
Various genotypes of L. quercina are randomly distributed across trees in both native and human-altered habitats and among all host species. Kohzar et al. say this is not surprising since all the host oak species are native to the region. Coast live oak is a major component of native forests and is also widely planted as a shade tree in residential areas. Furthermore, there has been no attempt to restrict the pathogen’s movement by adopting quarantines or other measures by phytosanitary agencies.
As a result, the inoculum can be moved across large distances by insects, birds, small mammals, and humans.
Bacterial pathogens can be associated with insects, relying on their feeding sites and other wounds to facilitate entry to the host’s tissues or for dissemination among hosts. In California, L. quercina might enter host tissue via wounds made by acorn weevils, filbertworms, and some cynipid wasps Kohzar et al.).
Colorado
The situation in Colorado is different. Significant dieback of exotic oaks planted in the state came to attention in the early 2000s. The hosts include non-native northern red oak, pin oak (Q. palustris), and Shumard oak (Q. shumardii). In Colorado, the bacterium causes “drippy blight disease” on the trees, not the acorns. The disease causes abundant ooze on symptomatic tissue. There has been a significant increase in tree mortality – with associated removal costs. The bacterium also has been found attacking Colorado’s one native oak, Q. gambelii; in this case, the pathogen attacks the acorns rather than the tree.
Due to small sample sizes, Kohzar et al. were unable to answer three key questions:
whether the Colorado L. quercina population comprises a new taxonomic species;
whether genetic variation in the bacterial populations are explained by the habitat (native or human-altered) or host; and
whether the L. quercina infections on native Q. gambelii serves as an inoculum reservoir for planted Q. rubra hosts or vice versa.
gambel oak; photo by Dave Powell, USDA Forest Service (retired); via Bugwood
Surprisingly, despite its more recent emergence, the Colorado population of L. quercina has higher genetic diversity. Kohzar et al. suggest this might be due to repeated introductions of the bacterium on nursery stock brought in from the northern red oak’s native range in the East. [see below]
As in California, L. quercina infections are associated with insects, especially kermes scale (Allokermes galliformis). This insect does not travel long distances, which might help explain why the Colorado genotypes are limited to nearby trees, not dispersed randomly as in California.
However, kermes scale has been present in the state for far longer than the disease. The scale’s population spiked at the same time as the drippy blight outbreak was detected. Kohzar et al. could not determine whether the rise in scale populations and associated increase in number of entry points through feeding sites led to the increase of bacterial populations, or vice versa.
Kohzar et al. did determine that the Colorado populations of L. quercina were not introduced from California. They cannot explain the original introduction but think there might be continuing introductions from the native range of both northern red oak and L. quercina – the northeastern United States. They call for further studies to understand evolutionary relationships among L. quercina populations from different areas, including the native habitat of red oak in the East to clarify possible causes and sources of the recent outbreak of drippy blight in Colorado.
Role of Environmental Conditions
Kohzar et al. stress the importance of factors other than species’ introductions to new environments as the cause of emerging forest diseases. They say such other factors as changes in environmental conditions, new host-vector associations, cryptic disease agents (e.g., pathogens with a very long latency period or endophytes changing their behavior to pathogenic), hypervirulent strains of known pathogenic species, and/or newly emerging species of unknown origin as key factors leading to disease emergence in forest ecosystems around the globe.
In the case of L. quercina in California and especially Colorado, Kohzar et al. point to stress on the trees caused by new environmental factors, e.g., rapid climate change. [Of course, oaks from humid regions of eastern North America are already outside their natural habitat in much-dryer Colorado.] They support this conclusion by noting the simultaneous appearance of four new diseases caused by Lonsdalea species in different parts of the world during the 1990s and early 2000s. These were Lonsdalea quercina in Colorado; L.britannica on oaks in Great Britain; L. iberica in Spain; and L. populi bark canker on poplar species in Hungary, China, and Spain. All cause similar symptoms of drippy blight disease.
Ewing, Curtis. Entomologist, CalFire. Pers. comm. March 2023.
Kozhar, O., R.A. Sitz, R. Woyda, L. Legg, J.R. Ibarra Caballero, I.S. Pearse, Z. Abdo, J.E. Stewart. 2023. Population genomic analysis of an emerging pathogen Lonsdalea quercina affecting various species of oaks in western North America. BioRxiv https://www.biorxiv.org/content/10.1101/2023.01.20.524998v1
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 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
spotted lanternfly; photo by Holly Raguza, PA Department of Agriculture
Environmental Entomology, in partnership with other journals from the Entomological Society of America, has published a special collection of papers on the spotted lanternfly, Lycorma delicatula. All papers in the collection are freely available to read and download through February 16, 2022. I will summarize key points, with brief references to the specific article.
An evaluation of spotted lanternfly survivorship on 26 host plant species in 17 families found that eight species supported development from first instar to adult: black walnut, chinaberry, oriental bittersweet, tree-of-heaven, hops, sawtooth oak, butternut, and tulip tree. When offered a choice between black walnut and tree-of-heaven, nymphs showed no preference; adults showed a significant preference for tree-of-heaven. [K. Murman et al. 2020. Distribution, Survival, and Development of Spotted Lanternfly on Host Plants Found in North America. Environmental Entomology, Volume 49, Issue 6, December 2020, Pages 1270–1281, https://doi.org/10.1093/ee/nvaa126]
Potential Controls: Parasites, Parasitoids, and a Pathogen
Significant efforts are afoot to find possible biocontrol agents. Scientists have surveyed SLF and associated parasites/parasitoids across 27 provinces and administrative regions of China from 2015 to 2019. They recovered an egg parasitoid, Anastatus orientalis, and a nymphal parasitoid, Dryinus sinicus, and are studying these further as potential biological control agents of spotted lanternfly. [B. Xin et al. 2020. Exploratory Survey of Spotted Lanternfly (Hemiptera: Fulgoridae) and Its Natural Enemies in ChinaEnvironmental Entomology, nvaa137, https://doi.org/10.1093/ee/nvaa137]
Nancy Dagli, USDI National Park Service, Bugwood.org
Nearly two years ago I posted a blog based on a study by Christopher Oswalt and colleagues (2016; source/link provided at end of blog) using data from the national Forest Inventory and Analysis (FIA) program of the United States Forest Service to determine what proportion of American forests are invaded by non-native plants. Nationwide, 39% of forested plots sampled contained at least one invasive species. Eastern forests are second in the density of invasive plants to Hawai`i, with 46% of plots invaded by at least one plant species.
FIA sampling plots are randomly located across the country. Plots are inventoried once every 5–7 years in the eastern U.S. and once every 10 years in the western U.S. The program inventories only plots that are at least 10% stocked by trees. Phase 2 (P2) plots represent approximately 6,000 acres; Phase 3 (P3) plots represent about 96,000 acres, except in some states and National Forests where there is a regional intensification of plots. Invasive plant species are measured on a subset of the field plots – on the P2 invasive plots, invasive plants of interest are recorded; on the P3 plots, all plant species (invasive, exotic, and native) are recorded.
The US Forest Service Northern Region (Region 9) has issued a report providing details for 50 invasive plant species on plots in the 24 states of the Region. (These states reach from Maine to the Dakotas, south to Kansas, then across to Delaware.) For this report, in states where both P2 invasive and P3 data were collected, the invasives data from the P3 plots were folded into the P2 invasive plots. When there were no P2 invasive plots for a particular inventory or species, the IPS data were calculated solely from P3 plots. In addition, the taxa reported varied over time and in some cases from state to state. Finally, the inventories took place over a period of years; the most recent inventories included in the report date from 2010. Presumably, the extent and intensity of plant invasions have increased in the intervening seven years. [The report is posted here.
Given the variety of plots inventoried, changes in taxa recorded, and time lag, the report cannot provide an up-to-date and detailed picture of any one site. However, it does allow us to get an overall picture that is more detailed than the nation-wide summary provided by Oswalt et al. 2016 and reported in Faith’s blog from spring 2016.
The report contains a wealth of data on the 50 individual species – a page for each, providing background, characteristics, distribution, monitoring data, and regulatory status in the various states. Also, there are 10 pages of summary tables. Since FIA inventories are conducted on the schedule of five to seven years, future reports based on these “[r]epeated measurements will help determine factors … associated with the presence of these species” and that the data can help “educate individuals of potential risk species”.
Our Interpretation
It is unfortunate that the USFS Southern Region has not prepared a similar report so that we could understand the extent of invasion by the individual taxa across the entire eastern deciduous forest. This is especially unfortunate because the Northern Region report found that the number of invasive plant species on a plot is higher in the southeastern portion of the Region (i.e., the states of West Virginia, Maryland, and Delaware). The arbitrary boundary between the Northern and Southern regions prevent our getting a true regional picture for the Mid-Atlantic states. The Oswalt et al. 2016 summary does allow some comparisons.
Still … we found it striking that seven of the 15 invasive plant species ranked highest in terms of proportion of plots invaded are shrub or vine species that were deliberately planted for improving wildlife habitat, horticulture, or other purposes.
Detailed Findings
The report does not state the proportion of all survey plots invaded by at least one invasive plant species for the region as a whole. Table 3 does report the proportion of plots in specific states. This varies from a high of 93% of plots in Ohio to a low of about 11% in Minnesota and New Hampshire. Several other Midwestern states also experience high levels of invasion: Iowa 81%, Indiana 79%, Illinois 72%, and Missouri 46%. Plots in Mid-Atlantic states and southern New England also are heavily invaded: West Virginia 79%, Maryland 65%, Pennsylvania 61%, Connecticut 54%, Rhode Island 51%, New York 49%, New Jersey 48%, Delaware 47%, Massachusetts 44%. In general, states in the far north have lower rates of invasion, like Minnesota and New Hampshire (above): Vermont 18%, South Dakota 15%, Michigan 14%, Maine 12%. However, North Dakota, at 29%, and Wisconsin, at 28%, differ from this generalization.
The most frequently recorded invasive plant is multiflora rose. According to the report, it is present in 39 states and five Canadian provinces. Across the region, multiflora rose is present on 16.6% of surveyed plots. It is the most common invasive plant in 10 of the 24 states of the region. It is almost ubiquitous in some states; in Ohio 85% of the plots were invaded. Oswalt reports that “roses” were the third most common invasive plants in the USFS Southern Region.
The third most frequently recorded invasive plant species is garlic mustard. It is reported to be present in 36 states and five Canadian provinces. Across the region, garlic mustard is present on 4.5% of the surveyed plots. Several states report high levels of infestation. In Ohio, garlic mustard is present on 30% of the plots; in Maryland, on 27% of the plots; in Pennsylvania, on 22% of the plots; in New Jersey, on 20%.
The fourth most frequently recorded invasive is common or European buckthorn. It is reported to be present in 34 states and eight Canadian provinces. Buckthorn is present on 4.4% of survey plots across the northeastern region – about a quarter of the plots on which multiflora rose is found. The highest proportion is in New York, where the invasive shrub is found on 16.8% of the plots.
Several bush honeysuckles rank high in the survey. Because of their close relationship and similar ecological impacts, we will discuss them together. Morrow’s honeysuckle is the fifth most commonly detected invasive plant species. This species is found on 3.8% of plots across the region. Amur honeysuckle ranks tenth; it is found on 3.1% of plots. Tatarian honeysuckle ranks sixteenth; it occurs on 1.5% of plots across the region. The hybrid showy fly, or Bell’s, honeysuckle ranks eighteenth; it occurs on 1.1% of plots. The data do not indicate whether there is much overlap in the plots invaded by the various species, so we cannot determine an overall invasion extent for bush honeysuckles – although clearly they occupy a significant proportion of the forest of the region. If there is almost no overlap, bush honeysuckles occupy 9.5% of all surveyed plots – second only to multiflora ros. During the first year of the survey, bush honeysuckles were recorded by genus – but only in four Midwestern states. In that survey, the genus was found on 6.5% of the plots surveyed.
The sixth most frequently recorded plant species is also an Asian honeysuckle – the vine Japanese honeysuckle, which is found on 3.6% of survey plots across the region. Oswalt et al. 2016 report that Japanese honeysuckle is the most common invasive plants in forests in the Southern region.
The second and seventh most frequently recorded plant species are native to parts of the region surveyed – although they have spread. These are black locust and reed canarygrass. We are confused as to how many of the reported plots actually represent invasions by these species since several states with high proportions of plots bearing black locust, for example, are in or next to the Appalachian mountains and the Ozarks, where the species is native.
The eighth and eleventh most frequently recorded invasive plant species are thistles — Canada thistle is eighth, bull thistle is eleventh. Both are found in more than 40 states and all 10 of the Canadian provinces. Each is present on approximately three percent of the plots, with concentrations in the upper Midwest.
The ninth and twelfth highest ranking invasive plant species in the region are additional shrubs which were deliberately planted for various purposes. Autumn olive ranks ninth; it occurs on approximately three percent of plots across the region. It is particularly dense in West Virginia, where it occurs on one fifth of all plots surveyed. Japanese barberry ranks 12th. It occurs on 2.4% of the plots across the region. In Connecticut, barberry is found on one-third of the plots.
The thirteenth most common species is common burdock – found on 2.2% of the plots. Again, the highest densities are found on forest plots in the upper Midwest along the edge of the prairie.
The fourteenth most commonly reported species is Nepalese browntop or Japanese stiltgrass. Stiltgrass has spread without much artificial assistance. Although stiltgrass is more common in the Southeast (outside the study region), it still occupies 2.1% of surveyed plots in the Northern region. Owald et al. 2016 report that stiltgrass is the fifth most common invasive plant in the Southern region.
Additional Studies Needed
The USFS Northern and Southern regions should coordinate their reports so that at least some use compatible methods and combine their findings so can see the picture for the entire Eastern forest.
USFS scientists should collaborate with other programs that map invasive plants – e.g., EDDMapS, the National Park Service, and Invasive Plant Councils – in both selection of species to target and developing an overall picture. As noted in Faith’s earlier blog, the Mid-Atlantic Invasive Plant Council has a list of 285 invasive plants in the region. Does the subset of 50 species selected for the FIA inventories provide an accurate picture of plant invasions in this sub-region?
Scientists should cooperate to evaluate the relative importance of propagule pressure v. forest fragmentation as factors in facilitating invasions. Their relative roles probably vary by species, receiving forest, etc.
We welcome the attention to invasions of interior forests – a topic previously neglected. Nevertheless, forest “edges” are also important ecologically – and – based on what we see in the Mid-Atlantic region – are even more heavily invaded. What impact does a wall of vines have on wildlife and plant species that evolved to live in area of greater light and temperature variation of trees, shrubs, herbaceous species that made up the edge before invasion?
Actions to Counter Plant Invasions
Those who sell plants for any use – ornamental horticulture, ground cover, livestock forage, soil amelioration, wildlife habitat management, biofuels – should commit to avoiding species that are known or suspected to be invasive in the region.
Voluntary efforts to limit sales of invasive plants have fallen by the wayside. The various Invasive Plant Councils should work with industry groups and others to renew this effort. Also, the Councils should propose a joint list of additional plants for APHIS regulation under NAPPRA (see below).
Those who buy plants for these various uses should make a similar commitment – especially large, institutional buyers like state highway departments.
Concerned citizens should lobby their state governments and the Congress to fund “noxious weed” programs and to ensure that these programs include plant species that threaten natural areas, not just weeds of agriculture.
Concerned citizens should lobby the Congress to increase funding for federal agencies’ invasive plant control programs, especially those addressing natural areas, and especially in Hawai’i and the eastern United States. Also, the U.S. Department of Agriculture needs to adopt procedures that enable APHIS to act more quickly to curtail introduction and human-assisted spread of invasive plants.
In June 2017, APHIS finalized its May 2013 proposal to restrict importation of 22 potentially invasive plant species – as provide by its NAPPRA program. (For a description of this program and the recent action, visit Faith’s blog here. APHIS should be empowered to use this program more aggressively to list additional plant taxa that appear likely to be invasive.
Source
Christopher M. Oswalt, Songlin Fei, Qinfeng Guo, Basil V. Iannone III, Sonja N. Oswalt, Bryan C. Pijanowski, Kevin M. Potter 2016. A subcontinental view of forest plant invasions. NeoBiota. 24: 49-54 http://www.srs.fs.usda.gov/pubs/48489
posted by Faith Campbell & guest Jil Swearingen
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.
Numbers of non-native pests in counties of the 49 continental states; Map prepared by Andrew Liebhold, USFS in 2014. More recent introductions are not represented; nor are insects native to some part of North America
Currently, the Northeast and Midwest have the highest number of non-native, tree-killing insect and pathogen species (see map above). However, Pacific coast states have two-thirds the numbers of pest species of the Northeast – and are catching up. Two articles modeling the likelihood of new pest introductions point to the particular vulnerability of the Pacific Coast states – especially California – to pest introductions from Asia.
Koch et al. 2011 (see reference at the end of the blog) utilized various sources of information about volumes of imports likely to be associated with wood-boring pests — stone; raw wood and wood products (including crates & pallets); metals; non-metallic minerals; auto parts; etc. From this, the authors estimated both a nationwide establishment rate of wood-boring forest insect species and the likelihood that such insects might establish at more than 3,000 urban areas in the contiguous U.S. While their estimate was based on 2010 imports, they also projected rates for 2020.
See my blog from March 10 for various scientists’ estimates of the overall, nationwide rate of introduction. Koch et al. estimated the nation-wide introduction rate at between 0.6 and 1.89 forest insects and pathogen species per year for the period 2001–2010 and 0.36 and 1.7 species per year for 2011–2020. In other words, we should expect a new alien forest insect species to become established somewhere in the United States every 2–3 years. If one-tenth of these new introductions turn out to cause significant damage, then we can expect a “significant” new forest pest every 5–6 years.
Pacific coast states – especially California – are at highest risk.
Koch et al. evaluated the introduction risk for 3,126 urban areas across the country. The metropolitan area with the highest risk is Los Angeles–Long Beach–Santa Ana, California. For both 2010 and 2020, the predicted rates for a new pest establishing there is every 4–5 years.
Looking ahead to 2020, the situation worsens for three California metro areas – Los Angeles–Long Beach–Santa Ana; San Diego; and Riverside-San Bernardino. At San Francisco-Oakland, the predicted establishment rates remain steady. Most of the rest of the top 25 urban areas show decreases in establishment rate between 2010 and 2020.
This rising risk to California urban areas is driven by the growth of imports from Asia. For the four California urban areas, the establishment rate of Asian species is projected to increase 6–8% between 2010 and 2020. The Los Angeles–Long Beach–Santa Ana area could potentially expect the establishment of an alien forest insect species originating specifically from Asia alone (not the entire world) every 4–5 years.
[The polyphagous and Kuroshio shot hole borers are examples of recently introduced pests from Asia. Both are described, inter alia, here; a distribution map for PSHB is available here.]
Koch et al. note that the Los Angeles metropolitan area has a dense human population with corresponding high demand for goods and materials, so a substantial proportion of imports clearing the port remains in the areas. Furthermore, widespread planting of non-native plants provides a range of potential hosts that can support invaders that would not otherwise become successfully established.
A second source also indicates a heightened risk to Pacific Coast states. Yemshanof et al. used similar modeling techniques to evaluate the risk of tree pest introductions to Canada … and to the U.S. in the form of transshipped goods. (See my earlier blog.)
The Yemshanof et al. model showed that 8% of all forest pests introduced to the U.S. on imported wood or wood packaging — as estimated by Koch et al. — would come through goods transshipped through Canada. The risk is highest to the Pacific Coast states since they are the most likely to receive Asian goods transiting through Canada.
Note that the phytosanitary agencies in both the U.S. and Canada proposed in 2010 that wood packaging originating in one of the countries and shipped to the other be required to meet the international regulations under ISPM#15. However, APHIS was unable to adopt this regulation under the Obama Administration, and such an action seems even less likely under the Trump Administration. Canada is unlikely to adopt the new rules without a coordinated U.S. action.
Southern California also imports lots of plants – another pathway for pest introductions.
Koch et al. suggest that authorities use these models to prioritize border control efforts (e.g., commodity inspections), post-border surveillance, and rapid-response measures. I see some problems with these suggestions. First, enhanced commodity inspections are not likely to measurably diminish the risk of introduction to the region. Second, rapid-response measures require both increased funds – which are expected to decrease; and political will. I have blogged several times about California’s decisions to not implement official, regulatory responses to recently detected pests.
Instead, people in the region should actively build alliances and press their regional political leaders – governors, mayors, senators, members of Congress – to demand that the U.S. Department of Agriculture and the Congress adopt policies that will strengthen protection for the region’s trees.
New pest detected in California!
California authorities have detected a new woodboring beetle – the olive wood borer (Phloeotribus scarabaeoides). It was detected in an olive tree in a grape vineyard in Riverside County. This is the first detection of the species in the Western Hemisphere. Known or suspected hosts include several trees in the olive family (Oleaceae), including olive trees, privet, ash, and common lilac; as well as oleander (Apocynaceae).
Since this new pest is native to the Mediterranean region, it does not appear to be an example of the risk to California from Asia … The source (Diagnostic Network News; see below) does not speculate on the pathway by which the introduction occurred.
What Can We Do?
Ask your state’s Governor to
Communicate to the USDA Secretary the need to amend policies & regulations
(Coordinate this effort with governors of other states.)
Put forest pest issue on the agenda of National Governors’ Association
Ask your state’s Congressional delegation to pressure USDA Secretary to amend policies and regulations
Communicate concern about these pests to the media — and propose solutions.
Ask your state’s agricultural and forestry agency heads to
Ask their national associations to support proposals to USDA Secretary & Congress. These associations include
National Association of State Departments of Agriculture (NASDA)
National Association of State Foresters (NASF) or its Western regional group, the Council of Western State Foresters
Communicate to the media both the agency’s concern about tree pest threats and proposed solutions.
We can also act directly.
Ask mayors and officials of affected towns and counties to
Push proposals at regional or National Conference of Mayors or National Association of Counties
Instruct local forestry staff to seek support of local citizen tree care associations, regional and national associations of arborists, Arbor Day & “Tree City” organizations, Sustainable Urban Forest Coalition, etc.
Reach out to local media with a message that includes descriptions of policy actions intended to protect trees — not just damage caused by the pests
Ask stakeholder organizations of which you are a member to speak up on the issue and support proposed solutions; e.g.,
Professional/scientific associations
Wood products industry
Forest landowners
Environmental NGOs
Urban tree advocacy & support organizations
Encourage like-minded colleagues in other states to press the agenda with their state & federal political players, agencies, & media.
Communicate to the media both your concern about tree pest threats and proposed solutions.
What Specific Actions Should We Suggest be Taken?
I suggest a coordinated package. However, you might feel more comfortable selecting a few to address each time you communicate with a policymaker. Choose those on which you have the most expertise; or that you think will have the greatest impact.
Make specific proposals, not vague ideas (see below for suggestions)
Always include information about how the pests arrive/spread (pathways such as imports of crates & pallets, or woody plants for ornamental horticulture) and what we can do to clean up those pathways (Don’t just describe the “freak of the week”)
Always point out that the burden of pest-related losses and costs falls on ordinary people and their communities. (Aukema et al. 2011 provides backup for this at the national level; try to get information about your state or city.)
We need to restore a sense of crisis to prompt action – but not leave people feeling helpless! We need also to bolster understanding that we have been and can again be successful in combatting tree pests.
Specific actions that will reduce risk that pests pose to our trees:
Importers switch from packaging made from solid wood (e.g., boards and 4”x4”s) to packaging made from other materials, e.g., particle boards, plastic, metal …
Persuade APHIS to initiate a rulemaking to require importers to make the shift. This can be done – although international trade agreements require preparation of a risk assessment that justifies the action because it addresses an identified risk (see my earlier blogs about wood packaging).
Create voluntary certification programs and persuade major importers to join them. One option is to incorporate non-wood packaging into the Department of Homeland Security Bureau of Customs and Border Protection’s (CBP) existing Customs-Trade Partnership Against terrorism (C-TPAT) program.
Tighten enforcement by penalizing shipments in packaging that does not comply with the current regulations
Persuade CBP and/or USDA to end current policy under which no financial penalty is imposed until a specific importer has been caught five times in a single year with non-compliant wood packaging. APHIS has plenty of authority to penalize violators under the Plant Protection Act [U.S.C. §7734 (b) (1)].
Restrict imports of woody plants that are more likely to transport pests that threaten our trees
In 2011, APHIS adopted regulations giving it the power to temporarily prohibit importation of designated high-risk plants until the agency has carried out a risk assessment and implemented stronger phytosanitary measures to address those risks. Plants deserving such additional scrutiny can be declared “not authorized for importation pending pest risk assessment,” or “NAPPRA”. A list of plants posing a heightened risk was proposed nearly 4 years ago, but it has not been finalized – so imports continue. APHIS should revive the NAPPRA process and utilize prompt listing of plants under this authority to minimize the risk that new pests will be introduced.
APHIS should finalize amendments to the “Q-37” regulation (proposed nearly 4 years ago) that would establish APHIS’ authority to require foreign suppliers to implement integrated programs to minimize pest risk. Once this regulation is finalized, APHIS could begin negotiating agreements with individual countries to adopt systems intended to ensure pest-free status of those plant types, species, and origins currently considered to pose a medium to high risk.
Strengthen early detection/rapid response programs by
Providing adequate funds to federal & state detection and rapid response programs. The funds must be available for the length of the eradication program – often a decade or more.
Engage tree professionals & citizen scientists more effectively in surveillance programs.
SOURCES
Koch, F.H., D. Yemshanov, M. Colunga-Garcia, R.D. Magarey, W.D. Smith. Potential establishment of alien-invasive forest insect species in the United States: where and how many? Biol Invasions (2011) 13:969–985
Western Plant Diagnostic Network First Detector News. Winter 2017. Volume 10, Number 1.
Yemshanov, D., F.H. Koch, M. Ducey, K. Koehler. 2012. Trade-associated pathways of alien forest insect entries in Canada. Biol Invasions (2012) 14:797–812
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.
A new film demonstrating the impact of non-native tree-killing insects and diseases will be shown on or around Arbor Day (April 20). You can help ensure that lots of people see the film!!! Contact the program manager at your local PBS channel to ask that the channel broadcast the film.
ash tree killed by EAB; Ann Arbor, MI; courtesy of Major Hefje
“Trees in Trouble: Saving America’s Urban Forests” focuses on emerald ash borer in Cincinnati. The film explores our connections to the trees and forests in our communities – and the threats to those trees. The film’s website links viewers to resources for taking action.
To see clips from the film and other resources go to this site.
The film was produced by Torrice Media. Featured experts and speakers include Prof. Dan Herms of Ohio State, Jenny Gulcik, a community forestry consultant, and Cincinnati Council member Wendell Young.
As we all know, killer pests threaten trees across the country, not just in southern Ohio! Such pests are usually introduced first in cities – not necessarily ports! – because that is where crates and pallets, imported ornamental plants, and other articles to which pests attach arrive. Furthermore, trees along streets and in yards and parks are often more vulnerable than forest trees to such introduced pests because they are often subject to other stresses such as soil compaction, air pollution, elevated temperatures, and salt exposure. Finally, city trees are often planted as multiple individuals of the same species; when a pest that attacks that species arrives, entire neighborhoods can lose their tree canopy – and the real values that canopy provides.
Because of the high value of urban trees, these pests’ greatest economic damage is in urban and suburban areas. The study by Julianne Aukema and others documented that municipalities spend more than $2 billion annually to remove trees killed by non-native pests. Homeowners spend $1 billion a year removing trees killed by non-native pests, and another $1.5 billion is lost in property values due to tree mortality.
Thus, it is vitally important that American city dwellers learn about the values that trees provide to them, the threat to those values from introduced pests, and what they can do to minimize this threat. “Trees in Trouble” is a tool to advance citizens’ understanding of these issues through a combination of broadcasts, compelling video presentations and active civic engagement efforts linked to the film.
goldspotted oak borer
Some people – less familiar with the issue than we are – do not immediately understand the relevance of Cincinnati’s story to other cities. We know that while the trees and killers differ across the country, the cost to the communities is the same: destruction of trees that provide shade and other important ecosystem services and create our sense of home. Plus, the ways these pests are introduced are the same – and so are the steps we can take to reduce this threat.
[The goldspotted oak borer illustrates the universality of this threat – trees in southern California are being killed, too!]
You can help overcome this roadblock! If you would like to help promote the film to your local PBS station or to local viewers, contact Andrea Torrice at 513-751-7050 or here
If you would like to obtain a copy of the film to screen to your group, contact Andrea Torrice at the same phone number or website. (Andrea is Italian; her name is pronounced “to re chay”, with the accent on “re”.)
Source:
Aukema, J. E., B. Leung, K. Kovacs, C. Chivers, K. O. Britton, J. Englin, S. J. Frankel, R. G. Haight, T. P. Holmes, A. M. Liebhold, D. G. McCullough, and B. Von Holle. 2011. Economic Impacts of Non-Native Forest Insects in the Continental United States. Plos One 6.
Experts have recognized for two decades that funding of federal programs intended to prevent or respond to introductions of invasive species is inadequate. As regards tree-killing insects and pathogens, there have been spikes in the past, spurred by, first, detection of Asian longhorned beetle and emerald ash borer, then by federal spending increases to support recovery from the Great Recession.
But with renewed pressure to reduce the federal budget, programs operated by APHIS and the USDA Forest Service have suffered significant cuts in spending. For a history of these cuts, read Chapter 3 in Fading Forests III .
Funding for key programs continue. Most alarming is that these cuts are suggested by the Administration! in its annual budget sent to Congress. I don’t know whether the cuts are suggested by the agencies, or instead are imposed by higher-ups in the Department of Agriculture or at the President’s Office of Management and Budget.
Certainly there is competition for the available funds. APHIS is funded by the Agriculture Appropriations bill, which also funds agriculture programs that enjoy strong lobbying support as well as food stamps. The Forest Service is being squeezed by the ever-higher costs of managing wildfires.
Still, these cuts threaten to expose our wildland, rural, and urban forests to permanent destruction by non-native, tree-killing insects and pathogens.
Congress determines the final funding levels through the appropriations process.
Members of Congress work for us!!
Ask your member of Congress & senators to support adequate funding for APHIS & USFS programs that counter invasive, non-native tree-killing pests.
Congress’ actions are at the following stage as of the third week in July:
APHIS
The House Subcommittee on Agricultural Appropriations bill had cut funding for “tree and wood pest” group – although the bill did increase funding for the “specialty crops” program.
In both cases, groups with which I work had asked to maintain the FY15 level.
The Senate bill, adopted by the full Appropriations Committee on 16 July, has restored funding to the “tree and wood pest” line! Possibly because of this increase, it holds the “specialty crops” program funding to the FY15 level.
Funding specifics:
HOUSE Agriculture appropriations bill maintains overall funding for APHIS at the FY15 level ($871 million). This is $15 million above the President’s request in his budget; and about the same as the level of funding for the current fiscal year (FY 2015). Within this amount, the following is allocated to programs that address tree-killing pests:
$158,000,000, to remain available until expended, for specialty crop pests
(a very small proportion of this account, about $5 million, goes to sudden oak death management)
$45,500,000, to remain available until expended, for tree and wood pests (e.g., ALB, EAB)
SENATE Agriculture appropriations bill raised overall funding for APHIS to $876 M — $20 million above the President’s budget request and $5 M above both the current year and House level. Within this amount, the following is allocated to programs that address for tree-killing pests:
$156,000,000, to remain available until expended, for specialty crop pests
$54,000,000, to remain available until expended, for tree and wood pests
As I said above, it is disturbing that these programs do not enjoy sufficient support within the Administration. We all need to increase our lobbying of USDA – both at the APHIS level and above; and at OMB.
USDA Forest Service
Both the House and Senate Interior Appropriations subcommittee bills cut USFS funding for both research and forest health management.
The House interior appropriations bill provides only $207 million for research other than Forest Inventory and Assessment. The Senate interior appropriations bill provides $211 million for research other than FIA. Both figures are below the $220 million allocated for the current year (FY2015) and higher levels in previous years.
The House bill provides only $99 million for forest health management (on both federal and non-federal or “coop” lands). The Senate bill provides $100.7 million. Again, both figures are below the $104.6 million provided in FY15 and higher levels in previous years.
Funding for all USFS programs is under extreme pressure by the growing cost of fighting wildfires. Until this problem is resolved, it will be extremely difficult to obtain additional funds for other programs – even in the face of rising numbers of tree-killing pests across the country. There are also questions within OMB and among some advocacy groups about whether the USFS should assist states and cities in containing tree-killing pests. Some argue that the USFS should confine its efforts to pests that are attacking trees in National forests. My reply: if you wait for ALB or other pests to reach National forests before responding, you have thrown away any chance of containing the outbreak.
