drivers of extinction – Page 6 – Center for Invasive Species Prevention

Support House & Senate bills to Enhance Response to Forest Pests

white ash: a species that might be restored under the programs envisioned in the proposed bills

Bills have been introduced into both the House and Senate to enhance USDA APHIS and Forest Service programs intended to curtail introduction and spread of non-native forest pests and disease and – especially – programs aimed at restoring pest-decimated trees to the forest.

The House bill is H.R. 3174; it was introduced by Reps. Becca Balint (VT).

The Senate bill is S. 1238; it was introduced by Senators Peter Welch (VT), Mike Braun (IN), and Maggie Hassen (NH). [Both senators Welch and Braun are on the Agriculture Committee – which will write the bill.]

CISP hopes that the contents of these two bills will be incorporated in the Farm Bill that Congress is expected to adopt this year or next. The proposals have the support of the Forests in the Farm Bill coalition. [Unfortunately, neither the “Consolidated Recommendations” nor “Summarized Recommendations appears to be posted on the internet at present.]

In the last Congress, a nearly identical bill introduced by then-Representative Peter Welch was endorsed by the organizations listed below. We hope they will endorse the new bills now! If you are a member of one of these organizations, please ask them to do so.

Organizations that endorsed the previous bill: Vermont Woodlands Association, American Forest Foundation, Center for Invasive Species Prevention, Reduce Risk from Invasive Species Coalition, National Woodland Owners Association (NWOA), National Association of State Foresters (NASF), The Society of American Foresters (SAF), the North American Invasive Species Management Association (NAISMA), the Ecological Society of America, Entomological Society of America, a broad group of university professors and scientists, The Nature Conservancy (TNC) Vermont, Audubon Vermont, the Massachusetts Forest Alliance, the New Hampshire Timberland Owners Association, the Maine Woodland Owners Association, and the Pennsylvania Forestry Association.

I seek your help in generating support for incorporating these proposals into the 2023 Farm Bill. Please urge your representative and senators to co-sponsor the bills or otherwise support that action.

beech in a breeding experiment at The Holden Arboretum; photo by Jennifer Koch

Key points of the two bills:

They strengthen APHIS’ access to emergency funds. APHIS has had the authority to access emergency funds from the Commodity Credit Corporation since 2000. However, the Office of Management and Budget has often blocked its requests. See § 2, of the bills, EMERGENCY AUTHORITY WITH RESPECT TO INVASIVE SPECIES.
It creates two separate but related grant programs.
- The first grant program – in § 3. FOREST RECLAMATION GRANTS – funds research addressing specific questions impeding the recovery of tree species that are native to the US and have suffered severe levels of mortality caused by non-native plant pests or noxious weeds.
- The second grant program – in § 4. FOREST RESTORATION IMPLEMENTATION GRANTS – funds implementation of projects to restore these pest-decimated tree species to the forest. These projects must be part of a forest restoration strategy that incorporates a majority of the following components:

(1) Collection and conservation of native tree genetic material.

(2) Production of propagules of the target tree species in numbers sufficient for landscape-scale restoration.

(3) Preparation of planting sites in the target tree species’ former habitats.

(4) Planting of native tree seedlings.

(5) Post-planting maintenance of native trees.

§ 5 states that the absence of a national policy on addressing nonnative forest pests has resulted in their receiving a low priority within all Federal agencies. It then mandates a study to analyze agencies’ available resources, raise the issue’s priority, and improve coordination among agencies. This study is to be carried out by an independent institution, for example the National Academy of Sciences. The authors are to consult with specialists in entomology, genetics, forest pathology, tree breeding, forest and urban ecology, and invasive species management.
Funding for all three action components – the emergency response and both grant programs – would come from the Commodity Credit Corporation, so it would not be subject to the vagaries of annual appropriations bills.

Forest Restoration Alliance volunteers potting hemlock seedlings; photo provided by Fred Hains

Entities which could apply for the research grants (§ 3 of the bills) include Federal agencies; State cooperative institutions; academic institutions offering degrees in the study of food, forestry, and agricultural sciences; and non-profit organizations exempt from taxes under §501(c)(3) of the tax code. Types of research funded could include:

‘‘(A) biocontrol of nonnative pests & diseases or noxious weeds severely damaging native tree species [the bill does not specify, but Project CAPTURE identifies many qualifying species; see also my earlier blog];

‘‘(B) exploration of genetic manipulation of the plant pests or noxious weeds;

‘‘(C) enhancement of pest-resistance mechanisms of hosts; and

‘‘(D) development of other strategies for restoring individual tree species.

The maximum amount of such grants is $400,000 per year.

Entities which could apply for the implementation grants (§ 4 of the bills) include a cooperating forestry school; a land-grant college or university; a State agricultural experimental station; a 501(c)(3) organization. Funding would begin at $3 million for FY 2023 and rise to $10 million for FY 2026.

The Secretary of Agriculture would be guided in implementing these programs by two committees. One – the committee of experts – would constitute representatives of the USFS, APHIS, ARS & State forestry agencies. The second – the advisory committee – would be composed of representatives of land-grant colleges and universities and affiliated State agriculture experiment stations, forest products industry, recreationists, and professional forester, conservation, and conservation scientist organizations.

Port-Orford cedar seedlings at USFS Dorena Center – a model for success! Photo provided by Richard Sniezko

Please contact your Member of Congress (Representative) and senators to urge them to support inclusion of these provisions in the Farm Bill. [Remember: they work for us!] Telling them of your support for these bills is especially important if your Representative or Senator is on the Agriculture Committee. I list those legislators here:

State	HOUSE AGRIC COMM	SENATE AGRIC COMM
AL	Barry Moore	Tommy Tuberville
AR	Rick Crawford	John Boozman
CA	Doug Lamalfa John Duarte Jim Costa Salud Carbajal
CO	Yadira Caraveo	Michael Bennet
CT	Jahana Hayes
FL	Kat Cammack Darren Soto
GA	Austin Scott David Scott Sanford Bishop	Raphael Warnock
HI	Jill Tokuda
IA	Randy Feenstra Zach Nunn	Joni Ernst Charles Grassley
IL	Mike Bost Mary Miller Nikki Budzinski Eric Sorensen Jonathan Jackson	Richard Durbin
IN	Jim Baird	Mike Braun
KS	Tracey Mann Sharice Davids	Roger Marshall
KY		Mitch McConnell
MA	Jim McGovern
ME	Chellie Pingree
MI	Elissa Slotkin	Debbie Stabenow
MN	Angie Craig	Amy Klobuchar Tina Smith
MO	Mark Alford
MS	Trent Kelly	Cindy Hyde-Smith
NC	David Rouzer Alma Adams
ND		John Hoeven
NE	Don Bacon	Deb Fischer
NJ		Cory Booker
NM	Gabe Vasquez	Ben Ray Lujan
NY	Marc Molinaro Nick Langworthy	Kirsten Gillibrand
OH	Max Miller Shontel Brown	Sherrod Brown
OK	Frank Lucas
OR	Lori Chavez-Deremer Andrea Salinas
PA	Glenn Thompson	John Fetterman

SD	Dusty Johnson	John Thune
TN	Scott Desjarlais Brad Finstad
TX	Ronny Jackson Monica de la Cruz Jasmine Crockett
VA	Abigail Spanberger
VT	Peter Welch
WA	Marie Gluesenkamp Perez
WI	Derrick van Orden

Posted by Faith Campbell

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

For a detailed discussion of the policies and practices that have allowed 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

www.fadingforests.org

New Tool for Evaluating Insect Pests’ Possible Impacts: One Test Shows Great Potential for Identifying the Greatest Threats to our Forests

red spruce (*Picea rubens*) — the conifer at greatest risk; This grove is in Great Smoky Mountains National Park; photo by Famartin via Wikimedia Commons

Scientists have incorporated into the widely-used urban tree management tool, i-Tree, a tool to help predict the damage that an insect species little known in North America might cause to trees growing in a specific area if it is introduced. This tool is available to all here.

I rejoice that predictive tools are becoming widely available. The tool is obviously the result of a lot of work by participating scientists – who are listed below. I hope many of you will try it out! Perhaps you and your students can join efforts by the tool-development team, especially in analyzing insect species from Central America and Asia that have not yet arrived in North America? If you are interested in helping, contact Katheryn Thomas, Angela Mech, or Ashley Schulz; you can obtain their contact information by visiting their institution’s website. You might choose which insect species to evaluate by consulting your own or colleagues’ research, reviewing the refereed and grey literature, APHIS and CFIA interception databases, databases maintained by several countries, websites such as CABI, EPPO, etc.

The new tool might help create a more effective “early warning” system. Whether this happens depends on what others do now. Anyone – perhaps a staffer of a federal or state agency, or a city tree manager, or an academic – can apply the tool to meet his/her own objectives. If a more effective national or continental “early warning” system is to be created, someone needs to set up a process for conveying the findings to responsible federal or state/provincial agencies or even the scientific societies, e.g., Entomological Society (and, in the case of beetles transporting associated fungi, American Phytopathological Society). Perhaps the most challenging issue is to find an entity willing to receive these communications, review their accuracy, and – at a minimum – make the results accessible to phytosanitary agencies, interested public, etc. One possible entity is “PestLens”, a web-based early-warning system maintained by APHIS. The project’s objective is to provide early-warning information and facilitate a prompt, coordinated, and appropriate safeguarding response. PestLens posts alerts once a month. These are visible to anyone who subscribes. However, it remains unclear how often APHIS and state agencies act on the notices. The North American Plant Protection Organization (NAPPO) also hosts an alert system, but it records only official notices, leading to some absurdities. (E.g., NAPPO reported Mexico’s designation of the invasive shot hole borers as quarantine pests – without mentioning that they are well-established in California because neither APHIS nor California Department of Food and Agriculture has designated the insects as officially regulated.)

Those applying the tool need to have some knowledge and access to a range of scientific resources (including, in my view, people who can check the accuracy of the data entered into the system). Users must have appropriate skills to conduct some research into the insect and what it feeds on. Information required for the tool includes the following:

taxonomic information for the insect (Order, Family, Genus, Species)
the feeding guild of the insect (i.e., foliovore, gall, reproductive, root, sap, wood)
climate in the native range of the insect (i.e., Tropical, Dry, Temperate, Continental, Polar)
native range of the insect (i.e., Afrotropical, Australasian, Indomalayan, Neotropical, Oceanian, Palearctic Asia, Palearctic Europe)
the host trees of the insect in its native range (scientific name [Genus species]). The tool warns participants to include the full range of potential tree hosts – by listing either all or a representative sample. The tool will use this information to estimate the evolutionary distance between known native hosts and potential North American hosts using comprehensive phylogenetic tree of plants.

Clearly, those using the tool have their work cut out for them! The tool does provide definitions, descriptors, and drop-down lists for most of the factors, including insect orders and families, tree genera, geographic origins, and climate types. Users are now anticipated to be employees of federal and presumably state agencies; academics – even students!—and others who have the capacity to research what an insect feeds on in its native range.

This tool is intended to predict the probability that an insect species of concern – either newly detected in the country or thought likely to invade based on port detections or other reasons — will become a high impact invader. I rejoice that they are inclusive – the tool can test the vulnerability of 50+ conifer species and 360+ hardwood species native to North America. Assuming the assessor can enter accurate information for the categories outlined above, the tool can then provide a list of probabilities for each relevant North American host tree.

The tool is based on the findings of two studies, Mech et al. and Schulz et al. (full citations at the end of this blog). I discussed these studies in earlier blogs. They were also incorporated into the broader effort to identify predictive traits carried out by Raffa et al. (full citations at the end of this blog) and discussed in a separate blog. See the section titled “Potential” to see the exciting results of an application of the Mech et al. findings and methods.

To develop the tool, project scientists synthesized data on traits and factors representing four types of drivers: (1) insect traits, (2) tree traits (especially those associated with host defenses), (3) the relatedness between the insect’s native and North American tree hosts, and (4) the relatedness between the non-native insect and North American insects on the same tree. They tested key hypotheses, e.g., defense free space and enemy release. The team tested the tool with researchers from USDA APHIS and Canadian Food Inspection Agency (CFIA), Northeast Plant Diagnostic Network, and National Invasive Species Council.

Norway spruce (*Picea abies*) — host of 30 of the 62 insect species analyzed in Uden *et al*.; photo by Marzena via Pixabay

The research group hopes this tool will stimulate development of a global database of insects which will utilize the results of basic research on phytophagous insects and what they eat. Basic research on insects native to North America is also important and can benefit other countries that might want to develop a similar tool for their own phytosanitary needs.

The Tool’s Potential

Many of the scientists who developed the i-Tree tool have participated in an analysis of the threat to North American conifer species posed by insects native to Europe that have not yet been introduced to North America (Uden et al.). They applied the methodology from Mech et al., which is comparable to, although not identical to, the i-Tree system. They (1) created a list of 62 European insect species that appear to pose a risk to 47 species of North American conifers; (2) identified and compared the predicted likelihoods of high-impact invasion under each of four phylogenetic systems datasets; and (3) evaluated risk and vulnerability trends among insects & conifer hosts, respectively. In total they evaluated 2,914 insect–novel host pairs.

Fraser fir (*Abies fraseri*) in Great Smoky Mountains National Park; photo by James St. John via Flickr

Among their findings are the following:

Of the 2,914 pairs examined, 302 (10.4%) had a predicted risk of high impact. These pairs included 41 (66%) of the insect species and 20 (41.7%) of the conifer species. The proportion of potential invasions posing a significant risk is higher than those indicated by earlier studies.
The insect species posing a risk of high-impact invasion were spread among insect orders, with relatively high levels concentrated in Lepidoptera and Coleoptera, fewer in the Hymenoptera and Hemiptera.
Consistent with Mech et al., they found a “Goldilocks” period of evolutionary divergence of hosts exposing the North American tree species to the highest risk. Thus, if a North American conifer shared a common ancestor with the insect’s native European host ~2–10 million years ago, it was predicted to be more vulnerable to a high-impact invasion by a conifer specialist.
North American fir (Abies) and spruce (Picea) species are more vulnerable to the introduction of European conifer-specialist insects than are pines (Pinus). [Mech et al. found that trees with high shade tolerance and low drought tolerance are more vulnerable. These traits also fit fir and spruce; but not pine.] The most vulnerable tree species was red spruce (Picea rubens).

Uden et al. also say Fraser fir (Abies fraseri) and Carolina hemlock (Tsuga caroliniana) are highly vulnerable to European insect species. They identified 17 high-risk insect species for Fraser fir. Of course, both are already severely depleted by non-native insect pests (Balsam woolly adelgid and hemlock woolly adelgid, respectively). They have also been identified by the Potter et al. “Project CAPTURE” process as having high priorities for conservation efforts.

I worry that fir and spruce are less important as timber species than pines; I hope this does not result in agencies and important stakeholders assigning this risk finding a lower priority.

Uden et al. assert that their study shows that this system can identify vulnerable tree species in the absence of information about which particular insect might invade. This information helps managers focus biosecurity and management program programs on protecting the most vulnerable tree species. However, 57% of the North American conifers (27 species) were found to be vulnerable under at least one of the insect-host pairs. To further set priorities, they suggest combining predictions from this analysis with USFS Forest Inventory and Analysis (FIA) data to identify vulnerable biogeographic regions and vegetation communities. (Fraser fir and Carolina hemlock rank high under this process.) Scientists could also apply species importance indicators, such as the NatureServe Explorer plant community descriptions. They suggest linking these criteria to the USFS Early Detection Rapid Response surveillance program, link to website which currently targets specific insect species.

red pine (*Pinus resinosa*) – the pine species at greatest risk; photo by Charles Dawley via Flickr

Uden et al. also warn that their analysis focused on a narrow range of possible introduced species: insects from Europe that feed on conifers exclusively. They caution that no one should assume that tree species that have a low “vulnerability” rank in this study should be considered at low risk for all possible introduced insects. They suggest researchers should identify tree species from the wider Palearctic that are within the high-impact “Goldilocks” zone of divergence times in relation to specific North American tree species, and then identify the insects that feed on those Palearctic trees to determine the species that would have the highest predicted risk of causing a high impact on those North American conifers.

Of course, many North American tree species are not conifers! Applying the methods in Schulz et al. – now integrated into the i-Tree tool – would facilitate similar predictive findings for the angiosperms.

Participants

The importance of this project is seen in the impressive array of funders supporting it. They include:

U.S. Geological Survey John Wesley Powell Center for Analysis and Synthesis for a working group titled “Predicting the nest high-impact insect invasion: Elucidating traits and factors determining the risk of introduced herbivorous insects on North American native plants;”
USDA Forest Service National Urban and Community Forestry Advisory Council funded a working group titled “Forecasting high-impact insect invasions by integrating probability models with i-Tree from urban to continental scales”;
Nebraska Cooperative Fish and Wildlife Research Unit;
University of Washington;
USDA Forest Service Eastern Forest Environmental Threat Assessment;
National Science Foundation Long-Term Ecological Research program;
USDA Forest Service International Programs; and
USDA National Institute of Food and Agriculture (Hatch and McIntire-Stennis projects).

Scientists who created this tool:
Kathryn A. Thomas (USGS – Southwest Biological Research Center)
Travis D. Marsico (Arkansas State University)
Daniel A. Herms (The Davey Tree Expert Company)
Patrick C. Tobin (University of Washington)
Andrew Liebhold (U.S. Forest Service)
Nathan Havill (U.S. Forest Service)
Angela Mech (University of Maine)
Ashley Schulz (Mississippi State University)
Matthew Ayres (Dartmouth College)
Kamal Gandhi (University of Georgia)
Ruth A. Hufbauer (Colorado State University)

Kenneth Raffa (University of Wisconsin) Daniel

Uden (University of Nebraska-Lincoln)

Carissa Aoki (Maryland Institute College of Art)

Scott Maco (The Davey Tree Expert Company)

Angela Hoover (University of Arizona)

SOURCES

Mech, A.M., K.A. Thomas, T.D. Marsico, D.A. Herms, C.R. Allen, M.P. Ayres, K.J.K Gandhi, J. Gurevitch, N.P. Havill, R.A. Hufbauer, A.M. Liebhold, K.F. Raffa, A.N. Schulz, D.R. Uden, and P.C. Tobin. 2019. Evolutionary history predicts high-impact invasions by herbivorous insects. Ecol Evol. 2019. Nov; 9(21):12216-12230.

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

Raffa, K.F., E.G. Brockerhoff, J-C Gregoire, R.C. Hamelin, A.M. Liebhold, A. Santini, R.C. Venette, and M.J. Wingfield. 2023. Approaches to Forecasting Damage by Invasive Forest P&P: A Cross-Assessment. BioScience Vol. 73 No. 2: 85–111 https://doi.org/10.1093/biosci/biac108

Schulz, A.N., A.M. Mech, M.P. Ayres, K. J. K. Gandhi, N.P. Havill, D.A. Herms, A.M. Hoover, R.A. Hufbauer, A.M. Liebhold, T.D. Marsico, K.F. Raffa, P.C. Tobin, D.R. Uden, K.A. Thomas. 2021. Predicting non-native insect impact: focusing on the trees to see the forest. Biological Invasions.

Uden, D.R, A.M. Mech, N.P. Havill, A.N. Schulz, M.P. Ayres, D.A. Herms, A.M. Hoover, K.J. K. Gandhi, R.A. Hufbauer, A.M. Liebhold, T.D. M., K.F. Raffa, K.A. Thomas, P.C. Tobin, C.R. Allen. 2023. Phylogenetic risk assessment is robust for forecasting the impact of European insects on North American conifers. Ecological Applications. 2023; 33:e2761.

Posted by Faith Campbell

www.fadingforests.org

Let’s Not Dismiss Conservation of Biodiversity While Seeking Carbon Storage in Forests

red deer on farm in New Zealand; photo by Bernard Spragg via Flickr

Among the non-native species damaging forest systems are mammals – introduced deer, goats and sheep, and swine, … These animals have the greatest impacts on island systems that are sufficiently isolated that they have no native terrestrial mammals, e.g., Hawai`i and New Zealand. Several New Zealanders have published a study of their impacts (Allen et al.; full citation at end of the blog). The focus of their analysis is the native forests’ ability to sequester carbon and thus mitigate climate change. The scientists are well aware, however, that forests provide many other ecosystem values and services, including biodiversity, water supply and quality, etc.

Introduced ungulates can have many direct effects: reduction and damage to understory biomass, depletion of seedling regeneration, exacerbated soil erosion, and local nutrient imbalances. Mammals’ browsing can modify the composition of plant communities by favoring abundance of unpalatable species. Changes also can alter ecosystem functions associated with nutrient cycling, e.g., by reducing nutrient returns to the soil and altering rates of litter decomposition

In these ways, introduced ungulates exert long-term impacts on forests’ capacity to store carbon.

Allen et al. aimed to determine the extent of these effects on forests’ capacity to store carbon, both above- and below-ground, and on forest structure and diversity. The authors compared data from 26 pairs of sites across New Zealand – half with ungulate exclosures and half adjacent unfenced control plots. The ungulate exclosures had all been established for at least 20 years. All the sites were in species-rich communities of conifers and broadleaved evergreen angiosperm trees. These forests (1) cover about one-third of the country’s remaining mature natural forest; (2) contain tree species of a wide range of palatability to ungulate herbivores; and (3) have been named a conservation priority for forest carbon management. The ungulates present on the plots were European red deer (Cervus elaphus), fallow deer (Dama dama), sika deer (Cervus nippon), and feral goats (Capra hircus).

They assert that New Zealand is a good place to do this type of study because ungulate introductions are relatively recent so their impacts are well documented.

Allen et al. found that managing invasive ungulates makes valuable contributions to conserving biodiversity but not to carbon sequestration. They found little difference in total ecosystem carbon between ungulate exclosures and unfenced control plots. Most of the difference they did find was explained by the biomass of the largest tree within each plot. As they point out, these large trees have been unaffected by invasive ungulates introduced during the last 20–50 years. However, they believe ungulate-caused changes in understory biomass, species composition, and functional diversity might result in major shifts in the diversity and composition of regenerating species. Hence, longer term consequences for both ecosystem processes and storage of forest carbon storage can be expected.

Indeed, excluding ungulates did increase the abundance and diversity of saplings and small trees. The basal area of the smallest class of tree size was 70% greater. Species richness of small trees and saplings was 44% and 68% higher, respectively. This difference had little impact on overall carbon storage, however, because the small trees and saplings store only about 5%. In contrast, the largest tree size class (dbh =/>30 cm), with their roots, contributed 44% of total ecosystem carbon in both exclosure and control plots. The largest effects of exclosures on carbon stocks were in early successional stands, e.g., those affected by such major disturbances as windthrow, volcanic activity, or landslides.

Climate change is expected to cause surprising interactions among forest productivity, herbivory, disturbance. Allen et al. suggest that authorities should focus on excluding ungulates on these highly productive regenerating forests rather than old-growth forests. I am disturbed by this suggestion. It exposes the most biologically diverse forests to continuing damage.

Data gaps

New Zealand has many long-lived, slow-growing tree species. Recruitment of understory trees is already low across both main islands. This situation has been attributed to ungulate browsing. Over centuries, this might result in shifts in the canopy composition. Allen et al. call for additional research to increase our understanding of how browsing and other short-and long-term drivers affect the regeneration of large trees. Also, data on soil CO₂ emissions needs better integration.

Australian brushtail possum; photo by Peter Firminger via Flickr

The study did not consider the impact of other introduced mammals, such as feral pigs (Sus scrofa), rodents, and Australian brushtail possum (Trichosurus vulpecula). The possum is known to damage New Zealand trees. The scientists did not explain this omission; I assume it might have been the result of either lack of resources to support a broader study or differences in management strategies – or both?

I note that the study also did not address the extent to which non-native pathogens threaten these large trees. In response to my query, Kara Allen said that their plots did not include many kauri (Agathis australis) trees, so the severe dieback disease caused by Phytophthora agathidicida did not affect their results. Naturally regenerating kauri is limited to a small area of warm temperate rainforests located at the top of the North Island. So kauri potentially play a relatively small role in terms of overall carbon stocks in New Zealand’s forests. On the other hand, Allen says that myrtle rust (Austropuccinia psidii) could have a major impact on New Zealand forests’ carbon storage. Trees in the host family, Myrtaceae, are ecologically important across both islands. Also, they comprise a large portion of overall forest carbon stocks (ranked in the top 5 largest families for above- and belowground biomass). An example is southern rata (Mterosideros umbellata), which are preferentially fed on by Australian brush possum.

Bernd Blossey, (free access!) who has long studied the role of high deer populations in North American forests, praises the study’s attempt to measure data, not just rely on models, and its inclusion of soil. However, he notes other limitations of the New Zealand study:

The small exclosures (20 x 20 m) are subject to edge effects. Some of Blossey’s exclosures occupy 2 hectares.
Twenty years is too short a time for analysis of such long-term processes as carbon sequestration and regeneration of slow-growing trees. Therefore, any results must be considered preliminary. Furthermore, no one recorded any differences in carbon sequestration of the paired plots at the time the exclosures were set up.
There’s no mention of possible impacts by introduced earthworms.

Dr. Blossey recognizes that the current study’s authors cannot re-do actions taken decades in the past. Still, the data gaps reduce the value of the findings.

I conclude that uncertainties continue due to: the long timelines of species’ regeneration and growth to full sizes; the requirement for large exclosures; the complexity of factors affecting carbon sequestration; and probably other influences.. Managers trying to maximize carbon sequestration are forced to act without truly knowing the best strategy or how their actions will affect the future.

For more about invasive mammals’ impacts in U.S. forests, also see the study by USFS scientists, Poland et al. (full citation listed in sources). One can enter “mammal” in the search box for the on-line PDF.

SOURCES

Allen, K., P.J. Bellingham, S.J. Richardson, R.B. Allen, L.E. Burrows, F.E. Carswell, S.W.Husheer, M.G. St. John, D.A. Peltzer, M. Whenua. 2023. Long-term exclusion of invasive ungulates alters tree recruitment and functional traits but not total forest carbon. Ecological Applications. 2023; e2836. https://onlinelibrary.wiley.com/r/eap

Poland, T.M., Patel-Weynand, T., Finch, D., Miniat, C. F., and Lopez, V. (Eds) (2019), Invasive Species in Forests and Grasslands of the United States: A Comprehensive Science Synthesis for the United States Forest Sector. Springer Verlag. The on-line version as at https://link.springer.com/book/10.1007/978-3-030-45367-1

Posted by Faith Campbell

www.fadingforests.org

Help Fight for $$ to Protect Forests

Help Fight for Money to Protect Forests

This blog asks YOU!!! to support funding for some of the key USDA programs. This blog focuses on USDA’s Animal and Plant Health Inspection Service (APHIS). APHIS is responsible for preventing introduction of pests that harm agriculture, including forests; and for immediate efforts to eradicate or contain those pests that do enter. While most port inspections are carried out by the Department of Homeland Security Bureau of Customs and Border Protection, APHIS sets the policy guidance. APHIS also inspects imports of living plants.

Please help by contacting your members of the House and Senate Appropriations Committees. I provide a list of members – by state – at the end of this blog. APHIS is funded by the House and Senate Appropriations Subcommittees on Agriculture and Related Agencies. These Subcommittees have scheduled hearings on the topic and I’ve drafted written testimony for them. I expect CISP will be joined by additional members of the Sustainable Urban Forest Coalition in signing the testimony. You can add the crucial voice of constituent’s support.

I will blog soon about funding for USDA’s Forest Service (USFS) – I don’t yet have necessary information to suggest specific funding levels.

Your letter or email need be no more than a couple paragraphs. To make the case for greater funding, feel free to pick-and-choose from the information that follows. Your greatest impact comes from speaking specifically about what you know and where you live.

These are the specific dollar amounts we’d like you to ask for. The rationale for each is below.

Appropriations for APHIS programs (in $ millions)

Program	FY 2022 (millions)	FY 2023	FY 2024 Pres.’ request	Our ask
Tree & Wood Pest	$61	$63	$64	$65 M
Specialty Crops	$210	$216	$222	$222 M
Pest Detection	$28	$29	$30	$30 M
Methods Development	$21	$23	$23	$25 M

The Costs of Introduced Pests

Introduced pests threaten many forest products and services benefitting all Americans, including wood products, wildlife habitat, carbon sequestration, clean water and air, storm water management, lower energy costs, improved health, aesthetic enjoyment, and related jobs. Already, the 15 most damaging non-native pests threaten at least 41% of forest biomass in the “lower 48” states. In total, these 15 species have caused an additional annual conversion of live biomass to dead wood at a rate similar in magnitude to that attributed to fire (5.53 TgC per year for pests versus 5.4 to 14.2 TgC per year for fire) [Fei et al.; full citation at end of blog; see also earlier].

tanoaks killed by SOD; Oregon Department of Forestry photo

These pests also impose significant costs that are borne principally by municipal governments and homeowners. As more pests have been accidentally introduced over time, these costs have risen. A study published last year [Hudgins et al.] projected that by 2050 1.4 million street trees in urban areas and communities will be killed by introduced insect pests. Municipalities on the forefront include Milwaukee and Madison Wisconsin; the Chicago area; Cleveland; and Baltimore, Towson, and Salisbury, Maryland. Removing and replacing these trees is projected to cost cities $30 million per year. Additional urban trees – in parks, on homeowners’ properties, and in urban woodlands – are also expected to die and require removal and replacement.

Pathways of Introduction

Tree-killing pests are linked to the international supply chain. Many pests—especially the highly damaging wood-borers like emerald ash borer, Asian longhorned beetle, polyphagous and Kuroshio shot hole borers, and redbay ambrosia beetle—arrive in inadequately treated crates, pallets, and other forms of packaging made of wood. Other pests—especially plant diseases like sudden oak death and sap sucking insects like hemlock woolly adelgid—come on imported plants. Some pests take shelter, or lay their eggs, in or on virtually any exposed hard surface, such as steel, decorative stone, or shipping containers.

infested wood from a crate; Oregon Department of Agriculture photo

Wood Packaging

Imports from Asia have historically transported the most damaging pests, e.g., Asian longhorned beetle, emerald ash borer, redbay ambrosia beetle, and the invasive shot hole borers. For decades goods from Asia have dominated imports. As of February 2022, U.S. imports from Asia were running at a rate of 20 million shipping containers per year. A recent analysis [Haack et al.; see also here] indicates that at least 33,000 of these shipping containers, perhaps twice that number, are carrying a tree-killing pest. These facts have led scientists to project [Leung et al.] that by 2050, the number of non-native wood-boring insects established in the US could triple. Hudgins et al. say the greatest damage would occur if an Asian wood-boring insect that attacks maples or oaks were introduced. Such a pest could kill 6.1 million trees and cost American cities $4.9 billion over 30 years. The risk would be highest if this pest were introduced to the South – and U.S. southern ports are receiving more direct shipments from Asia after the expansion of the Panama Canal in 2016. https://www.nivemnic.us/?m=202207

After introduction of the ALB, APHIS acted to curtail further introductions in wood packaging from China. First – in 1998 – APHIS required China to treat its wood packaging. Second, it worked with foreign governments to develop the International Standard for Phytosanitary Measures (ISPM) #15. The U.S. and Canada began phasing in ISPM#15 in 2005 with full implementation in 2006. Under ISPM#15, all countries shipping goods to North America must treat their wood packaging according to specified protocols with the goal of “significantly reducing” the risk that pests will be present.

However, as I have often blogged [see blogs under “wood packaging” category on this site] ISPM#15 has fallen short. Haack et al. found that as recently as 2020, 0.22% [1/5^th of 1 percent] of the shipping containers entering the U.S. were infested by a tree-killing insect. This equates to tens of thousands of containers harboring tree-killing insects.

Worse, the data indicate that our trade partners’ compliance with the rules has deteriorated; the “approach rate” of pest-infested wood packaging fell in 2005-2006, but has since gone back up.

The most troubling offender is China. Although required since 1998 to treat its wood packaging, China consistently has one of the highest pest approach rates: it was 0.73% [or ¾ of 1%] during the 2010- 2020 period. This is three times the global average for the period. Since China supplied 40.7% of U.S. imports in 2022 [Szakonyi], or 5,655,000 containers. Thus China alone might be sending to the U.S. 30,000 containers infested with tree-killing insects. These pests threaten our urban, rural, and wildland forests and reduce forest productivity, carbon sequestration, the rural job base, water supplies and quality, and many other ecosystem services.

ISPM#15 falls short at the global level. The fact that a pallet or crate bears the mark indicating that it complies with ISPM#15 has not proved to be reliable.

You might ask your Member of Congress or Senators to ask APHIS what steps it will take to correct the problem of Chinese non-compliance. (Remind him or her that that the Asian longhorned beetle, emerald ash borer, and many other insects of so-far lesser impact were introduced in wood packaging from China.

Asian longhorned beetle

Remind them also that the Department of Homeland Security’s Bureau of Customs and Border Protection has twice enhanced its enforcement of wood packaging rules. In 2017 it began penalizing importers of non-compliant wood packaging under Title 19 United States Code (USC) §1595a(b) or under 19 USC §1592. In 2021, it incorporated the wood packaging requirements into its voluntary C-TPAC program.)

You might also urge them to ask APHIS what steps it is taking at the global level to improve the efficacy of ISPM#15 – or to replace it if necessary to ensure that pests are not being introduced.

Imported Plants (“Plants for Planting”)

Some pest types—especially plant diseases like sudden oak death and sap-sucking insects like hemlock woolly adelgid—come on imported plants. The U.S. imported about 5 billion plants in 2021 [MacLachlan]. Recent introductions probably via this pathway include several pathogens — Phytophthoras, rapid ʻōhiʻa death in Hawai`i, beech leaf disease (established from Ohio to Maine), and boxwood blight. Insects have also been introduced on imported plants recently; one example is the elm zigzag sawfly (present in North Carolina, Virginia, and New York and Ontario). https://www.nivemnic.us/?p=4115

An analysis of data from 2009 [Liebhold et al.] found that approximately 12% of plant shipments were infested by a pest. This pest approach rate is more than 50 times higher than the 0.22% approach rate for wood packaging. APHIS has adopted several changes to its phytosanitary system for imported plants in the decade since 2009. A few studies have been published, but they have focussed on insects and excluded pathogens. We have noted that pathogens continue to be introduced via the plant trade. Therefore, please ask your Member or Senators to ask APHIS to facilitate an independent analysis of the efficacy of the agency’s current phytosanitary programs to prevent introductions of pests on important plants, with an emphasis on introductions of plant pathogens.

APHIS is responsible for preventing spread of the SOD pathogen, Phytophthora ramorum, through trade in nursery plants. In recent years California has had few detections in nurseries and little expansion in forests – but the situation suggests that this good news is probably more the result of the drought than of program efficacy. In cooler, wetter conditions in Oregon and Washington, detections in nurseries and alarming detections in the forest or plantings continue.

In 2022, the APHIS SOD Program supported detection and regulatory activities in 25 states. P. ramorum was detected at 18 establishment, 12 of which were first-time detections. The California nursery regulatory program – which is funded by APHIS – saw reduced funding in 2022. We think these cuts are unwise since this year’s very wet winter will probably lead to a new disease outbreaks. Programs in Oregon and Washington continue to detect infestations in additional retailers brought in by plants bought from other nurseries. Washington responded to four separate “trace forward” incidents, one involving more than 160 residential sites. Clearly, the federal-state program is not succeeding in eradicating P. ramorum from nurseries. Please suggest that your Congressperson and Senators ask APHIS what steps it is taking to improve the efficacy of the SOD program.

SOD-infected rhodoendron on plants in Indiana; photo by Indiana Department of Natural Resources

In the East, P. ramorum was found in three of 65 streams sampled in 10 states in 2022 (reaching across the Southeast from Mississippi through North Carolina, plus Texas, Maryland, Pennsylvania, and Illinois). One stream is troubling: a first-time detection in South Carolina, with no obvious nursery source. Since stream sampling began, P. ramorum has been detected from eight streams in four states, Alabama, Mississippi, North Carolina, and now South Carolina. The pathogen has been present in some of these streams for more than 10 years.

Oregon faces particularly high risks. Three of the four known strains of P. ramorum are established in Oregon forests. One of them, the EU1 lineage, is more aggressive than the NA1 clonal lineage already present in forests. In addition, the EU1 strain might facilitate sexual reproduction of the pathogen, thus exacerbating Oregon’s struggle to contain the disease.

As we know, introduced pests do not stay in the cities where they first arrived — they spread! Often that spread is facilitated by our movement of firewood, plants, or outdoor household goods such as patio furniture.

The beech trees so important to wildlife conservation in the Northeast are under attack by two pathogens and at risk to an insect. Most alarming is the spread – in a dozen years! — of beech leaf disease DMF from Ohio to Maine. A leaf-feeding weevil is spreading south in eastern Canada. Please suggest that your Member or Senators to ask APHIS what steps it is taking to prevent the weevil’s introduction to the U.S.

‘Ōhi‘a trees make up 80% of the biomass of forests in both wet and dry areas of the Hawaiian archipelago. It is under attack by two diseases caused by introduced pathogens first detected in 2010. ‘Ōhi‘a forests support more threatened and endangered species than any other forest system in the U.S. They also play a uniquely important role in providing other ecosystem services, including water supplies.

Asking for the Money Pest Problems Deserve

To respond effectively to these pests and to the others that will be introduced in coming years, the key APHIS programs identified above must have adequate funds. The funding levels I request – and hope you will support – are lower than I would wish, but everyone expects the Congress to refuse significant increases in funding (see table at beginning of this blog).

The Tree and Wood Pests account supports eradication and control efforts targeting principally the ALB and spongy (= gypsy) moth. Eradicating the ALB normally receives about two-thirds of the funds. The programs in Massachusetts, New York, Ohio, and South Carolina must continue until eradication succeeds.

Oregon detected the EAB in 2022. Although the state and Portland have been preparing for a decade for this eventuality, there will still be significant impacts. Four percent of Portland’s street trees are ash – more than 9,000 trees. Young ash constitute three percent of young trees in parks. Loss of Oregon’s ash will also have severe ecosystem impacts. In Willamette Valley wetlands, ash constitutes up to 100% of the forest trees. Washington and California are also concerned. Indeed, the Hudgins study identified Seattle and Takoma as likely to lose thousands of ash trees. The numerous ash in riparian forests, windbreaks, and towns of North Dakota are also at risk since the EAB is established in South Dakota, Minnesota, and Manitoba.

APHIS manages damaging pests introduced on imported plants or other items through its Specialty Crops program. The principal example is its efforts to prevent spread of the SOD pathogen through the interstate trade in nursery plants. We noted above that this program is not as successful as it should be. We support the Administration’s request for $222 million; however, you might suggest that your Member or Senator urge APHIS to allot adequate funding under this budget line to management of SOD, rapid ʻōhiʻa death pathogens in Hawai`i, and beech leaf disease and elm zig-zag sawfly in the East.

The Pest Detection program is key to the prompt detection of newly introduced pests that is critical to successful pest eradication or containment. The “Methods Development” program enables APHIS to improve development of essential detection and eradication tools.

The Administration’s request include a $1 million emergency fund. This is far below the level needed to respond when a new pest is discovered. Funding constraints have hampered APHIS’ response to past pest incursions.

Please note that many of the members of the Agriculture Appropriations Subcommittee are from states where non-native pests are probably not top of mind. It is important that everyone that knows about these threats communicate with your Member/Senators!!

Members of House or Senate Subcommittees that Fund APHIS

(Names of Senators are italicized)

STATE	MEMBER	APHIS APPROP	HOUSE	SENATE
AK	Lisa Murkowski			X
AL	Jerry Carl Katie Britt	X	X	X
Calif	Barbara Lee David Valadao Josh Harder Diane Feinstein	X X X	X X X	X
FL	Debbie Wasserman Scultz Scott Franklin	X X	X X
GA	Sanford Bishop	X	X
ID	Mike Simpson		X
IL	Lauren Underwood	X	X
KS	Jerry Moran	X		X
KY	Mitch McConnell	X		X
LA	Julia Letlow Ashley Hinson	X X	X X
MD	Andy Harris Chris Van Hollen	X	X	X
ME	Chellie Pingree Susan Collins	X X	X	X
MI	John Moolenaar Gary Peters	X X	x	X
MN	Betty McCollum	X	X
MS	Cindy Hyde-Smith	X		X
MT	Jon Tester Ryan Zinke	X	X	X
NB	Deb Fischer			X
ND	John Hoeven	X		X
NM	Martin Heinrich	X		X
NV	Mark Amodei		X
OH	Marcy Kaptur	X	X
OR	Jeff Merkley	X	X	X
PA	Guy Reschenthaler	X	X
RI	Jack Reed			X
TX	Michael Cloud Jake Ellzey	X	X X
UT	Chris Stewart		X
VA	Ben Cline	X	X
WA	Dan Newhouse Derek Kilmer	X	X X
WV	Shelly Moore Capito Joe Manchin	X		X X
WI	Mark Pocan Tammy Baldwin	X X	X	X

SOURCES

Fei, S., R.S. Morin, C.M. Oswalt, and A.M. 2019. Biomass losses resulting from insect and disease invasions in United States forests. PNAS August 27, 2019. Vol. 116 No. 35 17371–17376

Haack R.A., J.A. Hardin, B.P. Caton and T.R. Petrice .2022. Wood borer detection rates on wood packaging materials entering the United States during different phases of ISPM#15 implementation and regulatory changes. Front. For. Glob. Change 5:1069117. doi: 10.3389/ffgc.2022.1069117

Hudgins, E.J., F.H. Koch, M.J. Ambrose, and B. Leung. 2022. Hotspots of pest-induced US urban tree death, 2020–2050. Journal of Applied Ecology

Leung, B., M.R. Springborn, J.A. Turner, and E.G. Brockerhoff. 2014. Pathway-level risk analysis: the net present value of an invasive species policy in the US. Front Ecol Environ 2014; doi:10.1890/130311

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

MacLachlan, M.J., A. M. Liebhold, T. Yamanaka, M. R. Springborn. 2022. Hidden patterns of insect establishment risk revealed from two centuries of alien species discoveries. Sci. Adv. 7, eabj1012 (2021).

Szakonyi, M. 2023. Sourcing shift from China pulls US import share to more than a decade low.

Imports from China down slightly, but high pest risk continues

I have blogged often about the pest risk of wood packaging associated with imports from Asia – especially China – and the shift in that risk arising from import volumes and ports at which they are arriving (increasing volumes entering country at ports along Atlantic and Gulf coasts). [See blogs posted on this site, under the “wood packaging” category (listed below the archives by date).] As noted, U.S. imports from Asia are at all-time highs: in the first three months of 2022, they reached 1.62 million TEU (shipping containers measured as twenty-foot equivalents). This was 31.1% higher than in the same period in pre-pandemic 2019 (Mogelluzzo, B. April 22, 2022).

The most recent information (Szakonyi, M. 2023) confirms that U.S. importers are shifting suppliers to countries other than China, primarily because of lengthy shutdowns in Chinese factories linked to the “0 COVID” policy and some U.S. restrictions and tariffs. Over 2022 (full year), China – including Hong Kong – supplied 40.7% of U.S. imports. This is still a huge proportion, but lower than in 2021, when it was 42.4%. The Journal of Commerce calculates that the number of containers coming from China fell by 435,000. At the current rate of infestation in wood packaging from China calculated by Haack et al. 2022, that might mean about 1,200 fewer containers from China with infested wood packaging entering the U.S.

[Explanation of calculations: I divided 435,000 by 2 to convert 20-ft TEU into 40-ft containers that CBP encounters at the ports; multiplied the result by 0.75 – based on the decade-old Meissner estimate of % of containers that have SWPM; then multiplied the result by .0073 because that is infestation rate for China during 2010-2020 period]

This might be progress. China continues to have a terrible record of non-compliant wood packaging 23 years after U.S. and Canada instituted phytosanitary requirements. According to Haack et al. (2022), packaging from China made up 4.6% of all shipments inspected under the terms of their analysis, but 22% of the 180 consignments with infested wood packaging. Thus the proportion of Chinese consignments with infested wood is five times greater than expected based on their proportion of the dataset. The rate of wood packaging from China that is infested has remained relatively steady = 1.26% during 2003–2004, 0.73% during 2010 – 2020. And the insects present belong to the group that causes the greatest damage: longhorned beetles (Cerambycids). Indeed, 78% of beetles in this family that were detected were from China.

There is some good news: some types of goods likely to be enclosed in crates have decreased notably. The proportion of furniture and other home items imported from China has declined from 71.6% of all U.S. imports in 2010 to 52.6% in 2022. As Haack et al. (2022) found, crates are the type of wood packaging where wood pests are most commonly found. While crates constituted only 7.5% of the wood packaging inspected, they made up 29.4% of the infested packaging – or four times greater than their proportion of the dataset.

The pest risk might not be changing significantly, however, because some of the new suppliers are also in Asia. Vietnam’s share of U.S. imports rose from 8.2% to 8.7%. The types of goods most often imported from Vietnam included electronics, shoes, and apparel. The U.S. has already been invaded by insect-pathogen complexes native to Vietnam, Taiwan, and other parts of southeast Asia – e.g., redbay ambrosia beetle and laurel wilt; invasive shot hole borers and Fusarium disease.

U.S. imports from South Korea, mostly electronics and autoparts, climbed from 3.8% to 4.1%. Imports from India also saw a tiny increase – from 3.8% to 3.9%. These shipments were primarily apparel and iron and steel components. These goods prompt concern because wood packaging associated with heavy materials are often infested by insects (Eyre et al. 2018). The Haack et al. (2022) analysis found two interceptions of wood packaging from Vietnam, one from Korea, and three from India.

Besides, the Journal of Commerce notes that shifts in suppliers cannot go far. These countries’ manufacturing capacity and transportation infrastructure are far below those of China (Szakonyi, M. 2023).

In February 2023, U.S. imports from Asia continued to decline from record levels in 2021 and 2022 to 1.09 million TEU. This level still exceeds by 25% the 869,091 TEU recorded in March 2020, at the beginning of the COVID-19 shutdown (Mongelluzzo, March 17, 2023).

[Reminder: higher shares of imports from Asia are going to ports along the Atlantic and Gulf coasts – spreading the risk. See earlier blogs. In early March the Port of Savannah posted an advertisement to the on-line Journal of Commerce, crowing that by July it will complete straightening the river at the Garden City Terminal (the container terminal). This fix will enable Savannah to raise its annual container processing capacity by 1.5 million TEU, to 7.5 million.]

The most hopeful finding is that imports from Mexico jumped 19.2% in the first 11 months of 2022 compared to the same period in 2021. Importers have their reasons: a desire to buy from producers closer to the U.S. market. These motivations have nothing to do with the risk of forest pest introductions. However, we can rejoice because Mexico has greatly improved the pest-infestation rates of its exports since 2009. The rate fell from 0.29% in 2003-2004 to 0.04% in 2010-2020 (Haack et al. (2022).

larval Asian longhorned beetle; Thomas Denholm, NJ Department of Agriculture; Bugwood

I remain outraged that U.S. agencies have not taken effective steps to deal with the nearly 25-year-long problem of Chinese noncompliance with our phytosanitary requirements. As I noted in my previous blog, link to blog 303 Customs and Border Protection officials are disappointed that their enhanced enforcement in 2017 and 2021 has not yet resulted in improved compliance.

I suggested that the U.S. and Canadian government agencies should penalize trade partners with high records of not complying with ISPM#15. Among steps they should consider are

U.S. and Canada should refuse to accept wood packaging from foreign suppliers that have a record of repeated violations – whatever the apparent cause of the non-compliance. Institute severe penalties to deter foreign suppliers from taking devious steps to escape being associated with their violation record.
APHIS and CBP and their Canadian counterparts should provide guidance to importers on which foreign treatment facilities have a record of poor compliance or suspected fraud – so they can avoid purchasing SWPM from them. I greatly regret that the death of Gary Lovett might put an end to the voluntary industry program he had been developing, described here.
Encourage a rapid switch to materials that don’t transport wood-borers. Plastic is one such material. While no one wants to encourage production of more plastic, the Earth is drowning under discarded plastic. Some firms are recycling plastic waste into pallets.

Haack et al. 2022 fully describes the methodology used, the structure of USDA’s Agriculture Quarantine Inspection Monitoring (AQIM) program, detailed requirements of ISPM#15, the phases of U.S. implementation, etc. Also see the supplemental data sheet in Haack et al. (2022) that compares the methods used in each analysis.

SOURCES

Eyre, D., Macarthur, R., Haack, R.A., Lu, Y. and Krehan, H., 2018. Variation in inspection efficacy by member states of wood packaging material entering the European Union. Journal of Economic Entomology, 111(2), pp.707-715.

Haack RA, Hardin JA, Caton BP and Petrice TR (2022) Wood borer detection rates on wood packaging materials entering the United States during different phases of ISPM#15 implementation and regulatory changes. Frontiers in Forests and Global Change 5:1069117. doi: 10.3389/ffgc.2022.1069117

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

Mongelluzzo, B. Q1 US imports from Asia show no slowing in consumer demand. Apr 22, 2022. https://www.joc.com/maritime-news/container-lines/q1-us-imports-asia-show-no-slowing-consumer-demand_20220422.html

Mongelluzzo, B. US imports from Asia hit three-year low in February: data. https://www.joc.com/article/us-imports-asia-hit-three-year-low-february-data_20230317.html

Szakonyi, M. 2023. Sourcing shift from China pulls US import share to more than a decade low. https://www.joc.com/article/sourcing-shift-china-pulls-us-import-share-more-decade-low_20230201.html

Posted by Faith Campbell

www.fadingforests.org

Elm zigzag sawfly invades Eastern U.S.

The characteristic zigzag pattern Picture: Kelly Oten, NC State University.

Guest blog by Kelly Oten, NC State University

The elm zigzag sawfly [EZS; Aproceros leucopoda Takeuchi (Hymenoptera: Argidae)] is the newest invasive forest insect detected in the eastern US. The colloquially-used common name, currently going through the ESA common name approval process, is not only catchy, but perfectly describes this defoliator’s unique feeding damage. As EZS feeds on elm leaves, it weaves a zigzag pattern from the margin of the leaf towards the mid-vein.

An Expansive — and Quickly Growing – Range

Native to East Asia, the first confirmation of EZS in North America occurred in August 2020 in Québec, Canada when an iNaturalist user posted a photo showing the characteristic zigzag defoliation. The observer realized it was potentially EZS and emailed local entomologists in the province who visited the site, collected specimens, and obtained species confirmation through the Canadian Food Inspection Agency Entomology Lab (Martel et al. 2021). However, this detection was not actually the beginning.

Three months before the Canadian detection, the same defoliation pattern was observed in Frederick County, Virginia, USA. Observers suspected EZS, but no specimens were recovered and therefore identification could not be confirmed. A year later, the site was revisited and this time, bingo—specimens were present and confirmed as EZS. Subsequent surveys that summer led to detections in eight additional Virginia counties. At the same time, the telltale defoliation was observed in Lehigh County, Pennsylvania, USA, but no specimen could be recovered for confirmation. In 2022, EZS popped up more widely; four additional states confirmed EZS: Pennsylvania, North Carolina, Maryland, and New York.

Though new to North America, this insect has a history of invasiveness. First detected in Europe in 2003, it now occupies areas from the United Kingdom and France in the west, to Russia and Kazakhstan in the east (Ashikbayev et al. 2018, iNaturalist 2022).

The strange and unusual biology of elm zigzag sawfly

Like all Hymenopterans, EZS goes through four life stages: egg, larva, pupa, adult. Eggs are laid along leaf margins; after hatching, larvae feed on leaf foliage in a zigzag pattern towards the mid-vein. Older larvae consume the leaf more entirely, leaving behind the mid-vein and thicker lateral veins only. Before pupating, larvae spin a cocoon within which they pupate. Cocoons are seasonally dimorphic; summer pupae (which emerge as adults in 4-7 days) are net-like and attached to leaves or twigs. Overwintering pupae are solid-walled and found in leaf litter or soil. Interestingly, overwintering pupae are not just produced from the last generation of the year. Even early in the summer, overwintering pupae may develop alongside summer pupae. Adults are able to begin oviposition immediately; not only do they not need to feed, but they don’t need to find a mate either! EZS is parthenogenetic, meaning they reproduce without mating. In fact, no male EZS has ever been recorded and it’s believed the species is entirely female.

As elm zigzag sawfly larvae (bottom left on leaf) grow, they feed more wholly on elm leaves. Picture: Kelly Oten, NCSU

The entirety of this life cycle can last ~20-36 days when not overwintering. However, the voltinism of this pest is highly variable. Papp et al. (2018) recorded up to seven generations in a year on lab-reared colonies, but in nature in Europe, anywhere between two and six generations has been recorded (Blank et al. 2010, Mol and Vonk 2015). In Virginia, two generations were recorded in 2021 and 1 in 2022. It is unknown what factors play into the number of generations per year, but it’s clear that it’s highly variable. The ability of EZS to multiply rapidly and have multiple generations per year suggest large populations can build in a relatively short time. In fact, this was observed in North Carolina in 2022 and in Europe several times before. Large populations are capable of severe defoliation and may cause long-term impacts on tree health.

This collective life cycle description is based on Blank et al. 2010, Martel et al. 2021, Martynov and Nikulina 2017, and Wu 2006.

Spread

EZS has astonished many with how it seems to be popping up all over the place in such a short amount of time. Since 2020, it has been detected in five US states and at several sites along the St. Laurence River in the Canadian province. The adults are strong fliers, capable of spreading 45-90 km (~27-55 mi) per year (Blank et al. 2014). Given the fact they’re parthenogenetic, relatively small numbers can disperse to begin new populations. Of perhaps greater concern is the potential for long-range dispersal. In heavy infestations in North Carolina, cocoons were found not just attached to leaves and stems, but also non-living objects, suggesting a possible mechanism of long-range dispersal should they become attached to vehicles or other objects transported long distances. In addition, EZS damage ranges from minor to severe defoliation. When populations are low and feeding is minor, it’s less likely to be detected unless intentional surveys are conducted. This cryptic nature might suggest it’s in more places than we are currently aware.

An elm zigzag sawfly cocoon attached to a fence post.
Picture: Kelly Oten, NCSU

So, what’s the big deal?

In short, we don’t know yet. Generally speaking, defoliation by insects causes little long-term harm to tree health but severe and/or repeated defoliation can weaken or sometimes kill a host. In Europe, trees severely defoliated by EZS are typically able to re-leaf but may suffer branch dieback and/or reduced growth (Blank et al. 2010, Zandigiacomo et al. 2011). Also of note, EZS is attacking elm, an already-threatened tree due to widespread mortality cause by Dutch elm disease in the 1900s. Defoliation by EZS could further weaken infected trees or, at the very least, present an additional threat for remaining elms (Blank et al. 2010). While it seems aesthetic damage will be the primary concern with EZS, the potential for long-term tree health impactsin the US is uncertain and should be investigated. For now, anyone that finds EZS or its characteristic defoliation pattern are encouraged to report it to their respective state agriculture or forestry agency.

A row of winged elm (Ulmus alata) in NC were severely defoliated by elm zigzag sawfly.
Picture: Kelly Oten, NCSU

[See Faith’s earlier blog about the zigzag sawfly here.]

References

Ashikbayev, N. Z., N. S. Mukhamadiyev, G. Z. Mengdibayeva, M. B. Temirzhanov, and N. K. Kuanyshbaev. 2018. Development of forest entomology in Kazakhstan, pp. 42–47. In T. I. Espolov, K. M. Tireuov, E. I. Islamov, S. B. Baizakov, K. T. Abayeva, E. Z. Kentbaev, and B. A. Kentbaeva (eds.), Actual problems of sustainable development in forestry complex, vol. 2. Aitumar Publishing, Almaty, Kazakhstan.

Blank, S. M., H. Hara, J. Mikulás, G. Csóka, C. Ciornei, R. Constantineanu, I. Constantineanu, L. Roller, E. Altenhofer, T. Huflejt, and G. Vétek. 2010. Aprocerosleucopoda (Hymenoptera, Argidae): an East Asian pest of elms (Ulmus spp.) invading Europe. Eur. J. Entomol. 107: 357–367.

Blank, S. M., T. Köhler, T. Pfannenstill, N. Neuenfeldt, B. Zimmer, E. Jansen, A. Taeger, A.D. Liston. 2014. Zig-zagging across Central Europe: recent range extension, dispersal seed and larval hosts of Aprocerosleucopoda (Hymenoptera, Argidae) in Germany. J. Hymenopt. Res. 41: 57-74.

iNaturalist. Available from https://www.inaturalist.org. Accessed August 2022.

Martel, V., O. Morin, S. Monckton, C. Eiseman, C. Béliveau, M. Cusson, and S. Blank. 2021. Elm zigzag sawfly, Aproceros leucopoda (Hymenoptera: Argidae), recorded for the first time in North America through community science. Can. Entomol. 154: E1.

Martynoz, V. V., and T. V. Nikulina. 2017. Population surge of zigzag elm sawfly (Aproceros leucopoda (Takeuchi, 1939): Hymenoptera: Argidae) in the Northern Ciz-Azov Region. Russ. J. Biol. Invasions 8: 25-34.

Mol, A. W. M., and D. H. Vonk. 2015. De iepenzigzagbladwesp Aproceros leucopoda (Hymenoptera: Argidae), een invasieve exoot in Nederland. Entomol. Ber. 75: 50-63.

Papp, V., M. Ladányi, and G. Vétek. 2018. Temperature-dependent development of Aproceros leucopoda (Hymenoptera: Argidae), an invasive pest of elms in Europe. J. Appl. Entomol. 142: 589-597.

Wu, X. Y. 2006. Studies on the biology and control of Aproceros leucopoda. Plant Prot. 32: 98-100.

Zandigiacomo, P., E. Cargnus, and A. Villani. 2011. First record of the invasive sawfly Aproceros leucopoda infesting elms in Italy. Bull. Insectology 64: 145-149.

Protecting ash & hemlock – latest information

nearly dead ash in Shenandoah National Park; photo by F.T. Campbell

I participated in the annual USDA Interagency Invasive Species Research Forum in Annapolis in January 2023; as usual, I learned interesting developments. I focus here on updates re: efforts to protect ash and hemlock

Hopeful Developments re: countering EAB to protect ash

There are hopeful results in both the biocontrol and resistance breeding programs. The overall goal is to maintain ash as a viable part of the North American landscape.

Biocontrol

Juli Gould (APHIS) reminded us that the agency began a classical biocontrol program targetting emerald ash borer (EAB) in 2003 – only a year after EAB had been detected and much earlier than is the usual practice. [Thank you, former APHIS PPQ Deputy Administrator Ric Dunkle!] By 2007 scientists had identified, tested, and approved three agents; a fourth was approved in 2015.

Nicole Quinn (University of Florida) stressed that the egg prarasitoid, Oobius — if it is effective — could prevent EAB from damaging trees. However, it is so small that it is very difficult to sample. One small study demonstrated that Oobius will parasitize EAB eggs laid in white fringe trees (Chionanthus virginicus) as well as in ash. This is important because it means this secondary host is not likely to be a reservoir of EAB.

The numbers

According to Ben Slager (APHIS), more than 8 million parasitoids have been released at 950 sites since the program began in 2007. These releases have been in 418 counties in 31 states, DC, and four Canadian provinces. Still, these represent just 28% of infested counties. Parasitoids have been recovered in 21 states and two provinces.

Rafael de Andrade (University of Maryland) specified that these releases included more than 5 million Tetrastichus in 787 sites; ~2.5 million Oobius in 828 sites in 30 states; ~500,000 Spathius agrili – lately only north of the 40^th parallel. Releases of Spathius galinae began in 2015; so far ~ 470,000 in 395 sites.

Impact

Several presenters addressed questions of whether the agents are establishing, dispersing, and – most important – improving ash survival. Also, can classical biocontrol be integrated with other management techniques, especially use of the pesticide emamectin benzoate.

Dispersal

Several studies have shown that the four biocontrol agents disperse well (with the caveat that Oobius is very difficult to detect so its status is much less certain).

Implementation considerations

De Andrade found that the longer the delay between the date when EAB was detected and release of Oobius, the less likely Oobius will be recovered. Tetrastichus surprised because the higher the numbers released, the fewer were recovered. He could determine no association between recovery of S. agrili and variations in release regime [numbers released; delay in releasing biocontrol agents; or frequency of releases]. He said it is too early to assess Sp. galinae since releases began only in 2015, but he did see expected relationship to propagule pressure – the more wasps released, the higher the number that were recovered. Sp. galinae did surprise in one way: it seemed to perform better at lower latitudes. De Andrade noted he was working data from less than half of release sites. He asked collaborators to submit data!!!!

Initial signs of ash persistence and recovery

Claire Rutledge (Connecticut Agriculture Experiment Station) determined that

More large trees were surviving in plots where the biocontrol agents were released
EAB density was lower at long-invaded sites
Parasitism rates were similar across release age treatments and release/control plots

Gould focused on protecting saplings so they can grow into mature trees which could be sources of seeds to establish future generations. She noted that there are many “aftermath” forests across the northern United States – those dominated by ash saplings.

In Michigan, at a site of green ash, as of 2015 – 2021, EAB populations are still low, parasitism rate by Tetrastichus and S. galinae high. The percentage of saplings that remained healthy was greater than 80%. There were similar findings in white ash in New York: very low EAB larval density; and more than 70% of ash saplings had no fresh galleries. Gould reported that Tetrastrichus impcts could be detected within three years of release.

So, EAB are being killed by the biocontrol agents combined with woodpecker predation; but in their fourth instar, after considerable damage to the trees.

downy woodpecker in Central Park, NYC. photo by Steven Bellovin, Columbia University

Jian Duan reported on two long-term studies in green & white ash in Michigan and New England. His team used the most labor-intensive but best approach to determine EAB larval mortality and the cause – debarking trees – to determine whether the EAB larva were parasitized, were preyed on by woodpeckers, or were killed by undetermined cause, such as tree resistance, disease, or competition. In Michigan, he linked a crash of EAB population in 2010 was caused by Tetrastichus; EAB tried to recover, but crashed again, due to S. galinae. EAB larval densities had been reduced to 10 / m². Predation by abundant woodpeckers and the native parasitoid Atanycolus was also important.

In New England, EAB has also declined from 20-30 larvae /m² to ~ 10 m².

In Michigan, healthy ash with dbh of larger than 5 inches were much more plentiful in sites where parasitoids had been released. Their survival/healthy rate also was much higher in release sites but the difference declined as years passed. In New England there were growing numbers of healthy trees in 2021-22; (almost none in 2017). Duan conceded that he could not prove a direct link but the data points to recovery.

Tim Morris (SUNY-Syracuse) found that white ash saplings continued to die in large numbers, but the mortality rate was significantly below the rate in 2017. Canopy conditions varied; some trees that were declining in 2013 were recovering in 2017. Forty percent of “healthy” ash in 2013 continued recovering in 2021. Few living trees were declining; trees were either healthy or dead. He thinks probably a combination of genetics and presence of parasitoids explains which trees recover. Morris also reported some signs of regeneration.

beaver feeding on ash saplings, Fairfax County, Va;
photo by F.T. Campbell

At this point, I noted that in parts of northern Virginia, beavers have killed ash saplings. Morris reported finding the same in some sites in New York. Perhaps others have, also; my comment was greeted by laughter.

Theresa Murphy (APHIS) looked at integration of biocontrol and insecticide treatment in urban and natural sites. A study of black and green ash in Syracuse, NY Naperville, IL, and Boulder, CO found continued high parasitism by Tetrasticus and S. galinae and woodpecker attacks in trees treated with emamectin benzoate. Researchers could not detect Oobius. By 2020, most of the untreated trees had died but treated trees remained healthy.

Murphy has begun studying integration of biocontrol and pesticides in green and black ash forests. The goal is to protect large trees to ensure reproduction; the biocontrol agents do not yet protect the large trees. This is especially important for black ash because it declines very quickly after EAB invades. Sites have been established in New York, through collaboration with New York parks, Department of Environmental Conservation, and the Mohawk tribe. She is still looking for sites in Wisconsin – where EAB is spreading more slowly than expected.

1 of the infested ash in Oregon; photo by Wyatt Williams, ODF

Max Ragozzino of the Oregon Department of Agriculture reported on imminent release of biocontrol agents targetting the recently detected outbreak there. I am encouraged by the rapid response by both the state and APHIS.

EAB resistance in ash

Jennifer Koch (USFS) said the goal is not to produce populations where every seedling is fully EAB-resistant, but to develop populations of ash trees with enough resistance to allow continued improvement through natural selection while retaining sufficient genetic diversity to adapt to future stressors (changing climate, pests, diseases). The program has developed methods to quantify resistance in individuals.. Initial field selections of “lingering ash” were shown to be able to kill as many as 45 % of EAB larvae. Already green ash seedling families have been produced by breeding lingering ash parents. This first generation of progeny had higher levels of resistance, on average, than the parent trees. Each generation of breeding can increase the proportion of resistance. Although the bioassays to test for EAB-resistance are destructive (e.g., cutting and peeling to count numbers of surviving larvae), the potted ash seedling stumps can resprout. Once the new sprouts are big enough they are planted in field trials to correlate bioassay results with field performers. Poor performers are culled; those with higher levels of resistance remain and become sources of improved seed.

To ensure preservation of local adaptive traits, this process must be repeated with new genotypes to develop many seed orchards from across the species’ wide range. To support this work, concerned scientists are building multi-partner collaborative breeding networks. These organizations provide ways for citizens and a variety of partners to engage through monitoring and reporting lingering ash, making land available for test planting, and helping with the work of propagation.

See Great Lakes Basin Forest Health Collaborative » Holden Forests & Gardens (holdenfg.org), Monitoring and Managing Ash (MaMA) – A citizen-science-driven program for conservation and mitigation (monitoringash.org), and TreeSnap – Help Our Nation’s Trees! for more information.

Resistance levels in some of the first generation progeny were high enough for use in horticulture, where it is important that trees can remain healthy in challenging environments (street trees, city parks, landscaping, etc.). Koch hopes to develop about a dozen cultivars comprising the best-performing trees, appropriate for planting in parts of Ohio, Michigan, Indiana, and Pennsylvania. Local NGO partners are planting some of these promising genotypes in Detroit to see how they withstand EAB attack.

The threat to black ash is especially severe, and this species presents unique difficulties. While scientists found several seedlings from unselected seedlots had killed high levels of larvae, those deaths did not always result in better tree survival. Koch thinks the tree’s defense response becomes detrimental to tree by blocking transport of water and nutrients. She is working with experts in genomics and others, such as Kew Royal Botanic Gardens, to try to identify candidate trees for breeding programs. The genomics work has been supported by APHIS and the UK forest research agency, DEFRA. Michigan and Pennsylvania have supported the breeding work. USFS Forest Health Protection has supported work with black and Oregon ash (see below) (J. Koch, USFS, pers. comm.).

Koch has also begun working with Oregon ash, in collaboration with the USFS Dorena Genetic Resource Center (located in Cottage Grove, Oregon) and other partners.

dead hemlock in Massachusetts; photo by Ian Kinahan,
University of Rhode Island

Hemlock woolly adelgid

Scientists are still trying to find the right combination of biocontrol, chemical treatments, and silvicultural manipulation.

For several years, hope has focused on two has been on two predatory beetles, Laricobius nigrinus and L. osakiensis. Scott Salom (Virginia Tech) reports that release of these beetles over the past 20 years has had a significant impact on HWA density and tree photosynthetic rate and growth. However, Laricobius aredifficult to rear and they attack only the sistens generation of the adelgid. Ryan Crandall (University of Massachusetts) reports it has been difficult to establish these beetles in the Northeast. He links this difficulty is caused by temporary drops in HWA populations after cold snaps.

Scientists now agree that need to find predators that attack HWA during other parts of its lifecycle. Hope now focuses on silverflies — Leucotaraxis argenticollis and Le. piniperda. While both species are established in eastern North America, the clades in the east feed almost exclusively on pine bark adelgid, and have not begun attacking HWA. Biocontrol practitioners therefore collect flies in the Pacific Northwest for release in the east. Salom is increasing his lab’s capacity to rear silverflies and exploring release strategies.

Preliminary evidence indicates that the western clades of Leucotaraxis are establishing, although data are not yet definitive (Havill, USFS).

Detecting the presence of biocontrol agents presents several challenges. Tonya Bittner (Cornell) described efforts to use eDNA analysis for this. Some puzzles have persisted; e.g., at some sites, she detected eDNA but caught no silverflies. This raised the question of long eDNA associated with the original release might persist. Another problem is that the assay cannot separate the introduced western L. nigrinus from the native congener, L. rubus (which also does not feed on HWA). She continues efforts to improve this technique.

Others explored interactions of the biocontrol agents with insecticides. Salom is studying the impact of soil-applied insecticides on Laricobius populations, which aestivate in the soil. Preliminary results showed significant reduction in the beetle’s population under soil drench application but not under soil injection. He has not yet analyzed all the data.

Michigan is trying to prevent spread of HWA from five counties along the eastern shore of Lake Michigan (where HWA was introduced on nursery stock) to widespread hemlock forests in northern part of the state. Phil Lewis (APHIS) is studying persistence of systemic insecticides in hemlock tissues, particularly twigs and needles. The pesticides involved are imidacloprid, dinotefuran, and Olefin. He has found that pesticide levels are highest 18 – 22 months after treatment, then decline. They are significantly higher after trunk injection compared to bark spray or soil treatments. Imidacloprid had higher residues in twigs; dinotefuran in needles. This difference affects the likelihood of adelgids actually ingesting the toxin.

healthy hemlock in experimental gap; Jefferson National Forest, VA; photo by Bud Mayfield, USFS

Bud Mayfield (USFS) reported on his study of silvicultural strategies to support healthier hemlocks. While hemlocks normally thrive in shade, it has been determined that sunlight assists small trees reducing HWA sufficiently to counter the tree’s leaf-level stress. Small sapling hemlocks grown in sunlight fix more carbon and convert it to growth in shoots and trunk diameter.

Mayfield found promising immediate suppression of HWA in large gaps in Georgia and Tennessee. By the third year the saplings were still growing, although their faster growth had attracted more HWA. These findings were less clear farther north in central Virginia and western Maryland – Mayfield thinks because HWA pressure there is lower. However, managers must maintain the gaps by cutting rapidly-growing competing woody species. He plans to test this strategy farther north in Pennsylvania. He is still trying to determine the optimal size of the gap.

Posted by Faith Campbell

www.fadingforests.org

Can we work together to curtail introductions of new diseases?

Phytopthora ramorum-infected potted plants; photo by Washington State University

At this year’s USDA Invasive Species Forum I will be seeking to promote a discussion of what American and other stakeholders can do to suppress spread of forest pathogens. I have raised this issue many times before. To see my blogs about the P4P pathway, scroll down below the archives to the “categories”. See especially here and here.

I note that:

Non-native invasive pathogens and pests are decimating forests worldwide, threatening biodiversity & limiting efforts to rely on forests to alleviate impacts of climate change.
Many of the most damaging non-native organisms are pathogens that are especially difficult to detect at borders or to contain or eradicate once introduced.
A principal pathway by which pathogens are introduced is the international trade in living plants, or “plants for planting” (P4P).
Forest pathologists have long advocated a more pro-active approach – but national and international plant health officials have not taken up the challenge. [think Clive Brasier, Bitty Roy, Thomas Jung, Michael Winfield …]

*Austropuccinia psidii* on *Melalecua* in Australia; John Tann via Flickr

At the global level I suggest that we need:

National agricultural agencies, stakeholders, FAO & International Plant Protection Convention (IPPC) to consider amending IPPC requirement that scientists identify a disease’s causal agents before regulating it. I think experience shows that this policy virtually guarantees that pathogens will continue to enter, establish, & damage natural and agricultural environments.
National governments & FAO / IPPC to fund greatly expanded research to identify microbes resident in regions that are important sources of origin for traded plants, vulnerability of hosts in importing countries, and new technologies for detecting pathogens (e.g., molecular tools, volatile organic compounds [VOCs]).
Researchers & agencies to expand international “sentinel plants” networks; incorporate data from forestry plantations, urban plantings, etc. of non-native trees.
Application of ISPM#36 to promote use of HACCP programs for plants in trade. (See also my discussion in Fading Forests III – link at end of this blog.)

‘ohi‘a trees killed by rapid ‘ohi‘a death; photo by Richard Sniezko, USFS

We Americans need to

Evaluate efficacy of current regulations – incorporating NAPPRA & Q-37 revision. Rely on AQIM data. Include arthropods, fungal pathogens, oomycetes, bacteria, viruses, nematodes. Include threats to U.S. tropical islands (Hawai`i, Puerto Rico, Guam, etc.) which are centers of plant endemism.
Apply existing programs (e.g., NAPPRA, Clean Stock Network, post-entry quarantine) to strictly regulate trade in plant taxa most likely to transport pests that threaten our native plants; e.g., plants belonging to genera shared between North American trees & plants on other continents.
Recognize that plant nurseries are incubators for microbial growth, hybridization, and evolution; require nurseries to adopt sanitary operation procedures regardless of whether they sell in inter-state or intra-state commerce

I will explain my sense of urgency by noting the many recent introductions of pathogens – most probably via P4P or cut vegetation:

13 outbreaks of Phytophthora-caused disease in forests and natural ecosystems of Europe, Australia and the Americas. Three of four known strains of P. ramorum are established in U.S. forests.
Myrtle rust (Austropuccinia psidii) has been introduced to 27 countries, including the U.S., Australia, and South Africa.
Two new species of Ceratocystis (C. lukohia & C. huliohia)—causal agents of rapid ‘ohi‘a death (ROD) – spreading on the Hawaiian Islands. The former species appears to have originated in the Caribbean; the latter in Asia.
Since 2012, beech leaf disease has spread from northeastern Ohio to Maine.
Boxwood blight (caused by 2 ascomycete fungi, Calonectria pseudonaviculata & C. henricotiae) introduced to at least 24 countries in 3 geographic areas: Europe / western Asia; New Zealand, North America.
ash dieback fungus (Hymenoscyphus fraxineus) has spread across Europe after introduction from Asia.

What do you think? Can we find more effective methods to curtail introductions?

Posted by Faith Campbell

www.fadingforests.org

America & Russia – Sharing the Pests

*Platanus orientalis* in Turkey; photo by Zeynek Zebeci

A current issue of the journal Forests (2022 Vol. 13) is a special issue focused on forest pests. This topic was chosen because of increased pest incursions. Choi and Park (full citations at the end of the blog) link this to climate change and increased international trade, as well as difficulties of predicting which pests will cause damage where.

The journal issue contains 15 papers. Several patterns appear throughout. First is the important role of international trade in living plants – “plants for planting” – in introductions. This is hardly news! A second pattern is that at least two North American species were introduced to Europe during the 1940s, probably in wood packaging used to transport military supplies during World War II.

This compilation provides the opportunity to review which organisms of North American origin have become damaging invaders in Eurasia — and sometimes other continents. For example, the journal carries four articles discussing pine wilt disease (PWD). It is caused by the North American nematode Bursaphelenchus xylophilus, and is vectored by wood-boring insects in the genus Monochamus. Beetles introduced from North America and those native to the invaded area are both involved. This disease is considered a severe threat to forest health globally. No apparent association with WWII exists for PWD.

Two fungal pathogens from North America cause serious damage in urban and natural forests of Europe and central Asia. Neither is discussed in the special issue:

Ceratocystis platani has devastated urban trees in the Platanus genus, especially the “London plane” hybrid, and the native European tree, Platanus orientalis. This fungus was accidentally introduced to southern Europe during WWII – as were the two insects described by Musolin et al. It was first reported in northern Italy and Mediterranean France in the early 1970s, but disease symptoms had been observed years earlier. C. platani is established across the northern rim of the Mediterranean and to the east in Armenia and Iran. The worst damage has been in Greece, especially in natural forest stands in riparian areas. Spread of the pathogen there is facilitated by root grafts and by tree wounds caused by floating wooden debris during floods (Tsopelas et al. 2017.)

*Platanus orientalis* along Voidomatis River in Greece; photo by Onno Zweers, via Wikimedia

Heterobasidion irregulare infects conifers. It has spread and killed large numbers of Italian stone pine (Pinus pinea). The disease was inadvertently introduced to central Italy in the 1940s. H. irregulare has greater sporulation potential and decays wood more quickly than the native congener H. annosum. H. irregulare appears to be replacing the European species; scientists fear it will exacerbate tree infection and mortality rates (Garbelotto, Leone, and Martiniuc. date?)

A third North American pathogen, sooty bark disease (Cryptostroma corticale) has been introduced to Europe. This disease, found on sugar maple in eastern North America, was detected in Great Britain in 1945; it is now throughout Europe (Tanney 2022). EPPO reports that it is widespread in western Europe and in some Balkan countries. The website provides no information on its impact in Europe.

Pests in Russia

A paper authored by Musolin, et al. discusses 14 species of invasive or emerging tree pests found in Russian forest and urban ecosystems. Of these, two are native to North America. Another eight pose a threat to North America if they are introduced here.

As Musolin et al. point out, Russia covers a huge territory across Europe and Asia – stretching 10,500 km, or 6,500 miles. These encompass a great variety of ecological zones. Russia is also actively involved in international trade. It is not surprising, then, numerous non-native organisms have been introduced.

As of 2011, 192 species of phytophagous non-native insects from 48 families and eight orders were documented in the European part of Russia. This number does not include the vast areas in Asian Russia. Additional introductions have probably occurred in the most recent decade. Some of these introduced species have cause significant economic losses. Still, Russia appears to rarely mount a serious control effort.

Of course, the opposite is also true: pests native to some part of Russia can be transported to new regions of Russia or beyond its borders. We North Americans have focused on various species of tussock moths (Lymantria spp., etc.). There are many others. Musolin et al. describe eight in detail. All the information in this blog are from that article unless otherwise indicated.

Two North American Species’ Damage in Eurasia

Both these introductions were detected around the year 2000. Was there some event – other than simply expanding trade – that might explain these introductions?

*Leptoglossus occidentalis*; photo by nutmeg66 via Flickr

Western Coniferous Seed Bug, Leptoglossus occidentalis

This insect from western North America has invaded Eurasia, North Africa, and Central America. The first detection in Europe was in 1999 in Italy. It spread quickly and is present now from Morocco to Japan, as well as in South Africa and South America. The seed bug is spreading northward in European Russia, including into the forest-steppe zone. Its ability to spread to the East is uncertain.

L. occidentalis attacks a wide range of Pinaceae and Cupressaceae. In the Mediterranean region it has had serious impacts on the pine nut supply (Ana Farinha, IUFRO, Prague, September 2021). In southern parts of Russia it has caused “significant damage”. L. occidentalis also vectors a pathogenic fungus Sphaeropsis sapinea (=Diplodia pinea), which causes diplodia tip blight. The cumulative damage of insect and pathogen to pines can be significant.

The introduction pathway to Russia is unknown. It might have flown from established populations in Europe, or it might have been transported on plants for planting or Christmas decorations.

Oak Lace Bug, Corythucha arcuata

This insect is widespread in the United States and southern Canada. It was first detected in Europe – again, Italy – in 2000. Twenty years later it has spread to almost 20 countries.

Russia was invaded relatively recently; the first outbreak was detected in 2015 in the subtropical zone along the Black Sea coast and Caucasus. Musolin et al. expect the lace bug to spread to natural forests of Central Asia and other countries of the Caucasus. Its spread will be assisted by air currents and movement of plants for planting. The insect is causing considerable aesthetic damage, but other impacts have not been estimated.

Hosts include many species of oak (Quercus spp.), European and American chestnuts (Castanea spp.) plus trees from other botanical families: willows and maples (Salicaceae), redbay (Fagaceae), and alder (Betulaceae).

Pests in Russia that Could Damage North America if Introduced Here

*Malus sierversii*; photo by Lukacz Szczurowski via Wikimedia

Threat to Apples — Apple Buprestid, Agrilus mali

This Asian beetle has caused extensive mortality of wild apple (Malus sieversii) forests in Xinjiang, China. Wild apple trees are important components of deciduous forests in the Central Asian mountains. The species is also an ancestor of the domestic apple tree. Consequently, the borer is considered a potential threat to cultivated apple trees – presumably everywhere. A. mali might also attack other fruit trees in the Rose family, i.e., Prunus (plums, cherries, peaches, apricots, almonds) and Pyrus (pears).

Unlike most of the other species described here, A. mali is a quarantine pest in Russia and across Europe and the Mediterranean regions – the region where phytosanitary policies are coordinated by the European and Mediterranean Plant Protection Organization (EPPO). Russia bans imports of apple seedlings from infested areas.

China is reported to be experimenting with a possible biocontrol agent, Sclerodermus pupariae (a parasitoid of emerald ash borer).

Threat to Pines and Firs, Already Under Invasive Species Threats

Small Spruce Bark Beetle, Ips amitinus

This European beetle has been considered a secondary pest of dying conifers. Over the last 100 years, it has moved farther North. The first Russian record was 100 years ago, in the region where Russia, Belarus, and Ukraine meet. (Did military action during World War I play a role? This is not discussed by the authors.) By 2022, the beetle occupies 31 million ha. It is probably spread through transport of logs by rail.

In Western Siberia, the spruce beetle has attacked a new host, Siberian pine (Pinus sibirica).

The danger to North America arises from this beetle’s preference for five-needle pines (genus Pinus section Quinquefoliae). North America’s five-needle pines are already under severe pressure from the introduced pathogen white pine blister rust (Cornartium ribicola) and the native mountain pine beetle (Dendroctonus ponderosae).

Four-Eyed Fir Bark Beetle, Polygraphus proximus

This East Asian beetle feeds on firs (Abies spp.). Less commonly, it feeds on other genera in the Pinaceae: spruce (Picea ), pines (Pinus), larch (Larix), hemlock (Tsuga).

This beetle has been spreading west; the first substantiated record in European Russia was 2006 in Moscow. The beetle was probably present in western Siberia in the 1960s, although it was not detected until 2008. Again, the probable pathway of spread is movement of lumber by railroad.

P. proximus vectors an obligate symbiotic fungus, which can rapidly weaken the host. Musolin et al. comment on the beetle’s impacts – which they rarely do in this article. (Does this signify more damaging impacts, or availability of past studies?) They note significant changes in the forests’ ecosystem structure and microclimate, vegetation cover, and local insect fauna.

The danger to North America arises from this beetle’s preference for firs from the sections Balsamea and Grandis. Many North American firs are in these sections, including Fraser fir (Abies fraseri), balsam fir (A. balsamea), subalpine fir (A. lasiocarpa), grand fir (A. grandis), white fir (A. concolor), and others. Several of these firs already are challenged by the introduced balsam woolly adelgid. Firs in central and western Europe are less vulnerable since they are in the section Abies, which the beetle prefers less.

Threats to Poplars

Spotted Poplar Borer, Agrilus fleischeri

This boring beetle is native to northern Asia. It has caused significant mortality in native and exotic Populus plantations in China. Although there have been no reports of this beetle moving beyond its native range, many other Agrilus species have. Canada has twice intercepted adult spotted poplar borers on wood packaging. Musolin et al. fear that the adoption of non-native hosts might trigger an outbreak that would facilitate spread.

Poplar Leafminer, Phyllonorycter populifoliella

balsam poplar; photo by Matt Lavin via Flickr

This micromoth is widely distributed across the Palearctic. It was recently detected on introduced poplars growing in India.

The danger to North America arises from the beetle’s preference for black and balsam poplars. Several species in these taxonomic groups are common in North America, including Populus balsamifera, P. trichocarpa, P. deltoides, and Populus × Canadensis.

Threat to Oaks — Leaf Blotch Miner Moth, Acrocercops brongniardella

This micromoth is widely distributed in Europe and expanding to the north. The pest mines the leaves of several oak species (Quercus spp.), especially English oak, Q. robur; and sometimes European chestnut (Castanea sativa). Leaf blotch miner is considered one of the most important folivore insect pests of oaks in Russia. Damage has been greater in Omsk Oblast (Siberia), where both English oak and the micromoth are introduced species, than in St. Petersburg, which is on the northern limit of their natural range. Musolin et al. fear that the warming climate will lead to the pest causing greater damage in the northern portions of its range.

Threat to Basswood — Lime Leaf Miner, Phyllonorycter issikii

This Asian moth has been moving west since the mid-1980s. It now occupies most of European Russia with some outbreaks in Siberia. In Europe, it is a conspicuous pest of Tilia species.

In these invaded regions, the leaf miner has shifted to novel hosts, including American basswood (T. americana). Basswood is a common plant in the eastern deciduous forest of North America.

Threat to Horse Chestnuts & Urban Trees — Horse-Chestnut Leaf Miner, Cameraria ohridella

This tiny moth was unknown to science before the first recorded outbreak in the late 1980s. Over the next three decades it spread to most of Europe, where horse chestnut (Aesculus hippocastanum)has been widely planted for three centuries. It has caused significant damage.

The first Russian detection was in Kaliningrad, on the shores of the Baltic Sea, in 2003. The leaf miner now occupies 69% of administrative units of European Russia. It is considered one of the Top 100 most dangerous invasive species in Russia.

In North America, the moth might attack native horse chestnuts, Ae. octandra (=flava) and Ae. glabra. Urban plantings are at particular risk because the leaf miner might attack both European horse chestnuts and two non-native maples that have been planted widely, sycamore maple (Acer pseudoplatanus) and Norway maple (A. platanoides). Data cited by Musolin et al. are contradictory regarding larval development on the maples. Once introduced, the leaf miner is difficult to contain because it spreads through natural flight of adults, wind-blown leaves, hitchhiking on vehicles, and movement of infected plants.

Shared Pests

Russia has been invaded by two species that have been introduced in many countries (beyond pine wilt nematode). These two entered the country on plants for planting being imported to landscape venues for the XXII Winter Olympic Games – held in Sochi in 2014.

First to arrive was the Box Tree Moth, Cydalima perspectalis. This East Asian species was first detected outside its native range in Germany in 2006. By 2011 it was widespread in European and Mediterranean countries. In 2021, the boxwood moth was found in North America (first Canada, then the United States). [I discuss the boxwood moth briefly here.]

In Russia, box tree moth larvae were first recorded in 2012 on the planting stock of its principal host, Buxus sempervirens. The moth quickly spread around the Black Sea region and to the North Caucasus. It spread farther, too: it reached the Kaliningrad Oblast (southeast coast of the Baltic Sea) in 2020. The main pathway of C. perspectalis invasion was the introduction of infested box-wood planting material.

Further spread of C. perspectalis is likely from Russia into the natural forests across the Caucasus (Transcaucasia) and to countries located further south. This is most distressing because the region has extensive natural forests of Buxus sempervirens. In 2015–2017, C. perspectalis almost completely destroyed the natural boxwood populationsin these regions of Russia and further eastwards in Abkhazia. Boxwood stands in Georgia and northern Iran are already suffering intensive defoliation as the result of infection by two non-native pathogens, Calonectria pseudonaviculata [synonym Cylindrocladium buxicola] and Calonectria henricotiae. Damage to these forests could lead to reductions in soil stability and subsequent declines in water quality and flood protection, changes in forest structure and composition, and declines in Buxus-associated biodiversity (at least 63 species of lichens, fungi, chromista and invertebrates might be obligate). (In December 2022, Iryna Matsiakh presented a compelling overview of threats to these forests in a webinar sponsored by the Horticulture Research Initiative; apparently no recording is available.)

The second global invader to appear was the Brown Marmorated Stink Bug, Halyomorpha halys.

This insect from southeast and east Asia invaded the United States in 1996. The first detection in Europe was in Liechtenstein in 2004. In both cases, it spread quickly across these continents.

Russia’s first detection of stinkbug was in 2014 in parks in Sochi and elsewhere along the Black Sea coast. The spread in Russia appears to have been limited to the Black Sea – Caucasus area.

The brown marmorated stinkbug is highly polyphagous, feeding on more than 300 species of plants. In southern Russia, 107 species have been documented as hosts. At times, stinkbug feeding has caused severe losses in yields of fruit and vegetable crops.

Patterns

Musolin et al. stress the importance of the pest shifting to new hosts–usually from the same or a closely related genus. They cite several examples of these shifts occurring in the pest’s native range, including Agrilus planipennis (from local Asian ash species to introduced North American ash species); Phyllonorycter populifoliella and Agrilus fleischeri (from local poplars to widely cultivated introduced North American poplars and hybrids); Agrilus mali (from cultivated to wild apples).

As I noted above, the introduction and spread pathways are the usual ones: plants for planting (three species) and shipments of logs. There is one indication of wood packaging – Spotted Poplar Borer, Agrilus fleischeri at the Canadian border.

SOURCES

Choi, W.I.; Park, Y.-S. Management of Forest Pests and Diseases. Forests 2022, 13, 1765. https://doi.org/10.3390/f13111765

Garbelotto, M., G. Lione, and A.V. Martiniuc. date? The alien invasive forest pathogen Heterobasidion irregulare is replacing the native Heterobasidion annosum. Biological Invasions https://doi.org/10.1007/s10530-022-02775-w

Musolin, D.L.; Kirichenko, N.I.; Karpun, N.N.; Aksenenko, E.V.; Golub, V.B.; Kerchev, I.A.; Mandelshtam, M.Y.; Vasaitis, R.; Volkovitsh, M.G.; Zhuravleva, E.N.; et al. Invasive insect pests of forests and urban trees in Russia: Origin, pathways, damage, and management. Forests 2022, 13, 521.

Tanney, J. Forest Health Challenges Exacerbated by a Changing Climate: Swiss Needle Cast and Sooty Bark Disease in B.C. 65th ANNUAL FOREST PEST MANAGEMENT FORUM (Canada). December 7, 2022.

Tsopelas, P., A. Santini, M.J. Wingfield, and Z.W. de Beer. Canker Stain: A Lethal Disease Destroying Iconic Plane Trees. Plant Disease 2017. 101-645-658 American Phytopathological Society

Climate Change + CO2 Levels – Can Scientists Include the Complexity in their Analyses?

Spruce budworm (*Choristoneura fumiferana*); photo by Jerald E. Dewey, USFS; via Bugwood; populations of several forest birds, including Cape May, Tennessee and Bay-Breasted warblers, become more numerous during budworm outbreaks

Now that Drs. Ziska and Aucott have educated us about the strong impact atmospheric CO₂ can have on both plants and phytopagous insects, I have asked the experts whether these interactions have been incorporated in the models scientists are using to forecast pest activity in American forests as the climate changes.

The answer is no.

bay-breasted warbler; photograph by Dave Inman at Presque Isle State Park, PA; via Flickr

Dr. Bethany A. Bradley, Co-Director, Northeast Climate Adaptation Science Center at the University of Massachusetts, says empirical models of species range shifts typically only use climate and sometimes other environmental factors (like soils or topography) as predictors of potential geography. Inclusion of demographic processes like how plant growth is affected by more or less water, CO₂, competition with other plants etc. would require a lot of data. It is currently impossible since there are tens of thousands of plant species interacting in the forests of eastern North America – and perhaps these factors have been analysed for only a hundred of them.

Mike Aucott points to the same difficulty: inclusion of CO₂ in models of the future populations of specific plants would be difficult since the impacts vary from species to species and are compounded by other factors such as soil nitrogen levels, moisture levels, temperature, presence of competing plants, etc.

Regarding insects, Dr. Aucott thinks it is clear that some orders, such as Lepidoptera, don’t fare as well when feeding on plants grown under elevated CO₂. He is not aware of efforts to model impacts of high CO₂ on specific insects or even orders or feeding guilds.

juniper geometer (inchworm); Dr. Tallamy says inchworms are hairless & good tasting – so sought by birds

Dr. Ziska concurs about the difficulties. Dr. Ziska asks why there is so little funding to study these issues, especially given their probable impact on human food supplies and health – as described in his blog and an opinion piece published in Scientific American two years ago.

I hope that scientists, decision-makers, readers of this blog … maybe even the media! – take into consideration these complexities, even if they cannot be defined.

Posted by Faith Campbell

For a detailed discussion of the policies and practices that have allowed these pests to enter and spread – and that do not promote effective restoration strategies – [but do not address climate or CO2 aspects] review the Fading Forests report at http://treeimprovement.utk.edu/FadingForests.htm