Author: phytodoer@aol.com

Good News!!!! Treatments to Counter Beech Leaf Disease — at least for indidividual trees

beech leaf disease symptoms; photo by Matthew Borden via Flickr

Beech leaf disease (BLD) came to attention in 2012 near Cleveland. It has since spread to the Atlantic – Maine to New Jersey and northern Delaware; south into Virginia; north in Ontario; and west to eastern Michigan.

Scientists have scrambled to understand the disease – how it hijacks the tree’s metabolism;  & here its impacts on seedlings, saplings, and mature trees; how it spreads, locations at greatest risk.

(Maryland detections too recent to be shown)

Many of us have despaired.

Now Bartlett Tree Research Laboratories – the research arm of Bartlett Tree Experts – has announced development of Integrated Pest Management (IPM) strategies to treat individual trees – sadly not yet beech in the forest. The project is led by Dr. Andrew Loyd and Dr. Matthew Borden.

Seeing the disease’s impacts on a tree species with aesthetic and ecological values not easily replaced, and its rapid spread, scientists at Bartlett Tree Research Laboratories began testing fungicides and nematicides registered under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) by the U.S. Environmental Protection Agency (EPA) to see whether they might be effective against the causal nematode Litylenchus crenatae ssp mccannii.

As Drs. Loyd and Borden note, managing BLD presents numerous challenges:

1. The disease was discovered recently, so there were many unknowns, including how it spreads and the causal organism’s novel life cycle.

2. The damage occurs in leaf buds during winter dormancy. There has been little previous research on such a system. It is difficult for chemicals to reach the tissues.

3. Mature trees are large, so reaching the vulnerable leaves in the canopy is difficult.

4. Treatment efficacy cannot be evaluated until nearly a year after application.

5. Few chemicals are registered for use against foliar nematodes or for trees in forest, nursery, or landscape settings.

6. Obtaining funding is difficult because protecting beech is a low priority among many of the usual sources.

Fortunately, the leadership at Bartlett – the company’s research department, the New England Division leadership, and especially Robert A. Bartlett, Jr. (head of the family-owned company) – saw the importance of protecting beech and have supported this research. The USDA Forest Service has also funded some of studies exploring soil drenches. Cameron McIntire reports that these studies do not yet have results.

Furthermore, Bartlett has chosen to make the science easily available to all interested parties. Three posters explaining experiments to date are available at ResearchGate. They have also published a study on the early tests of Fuopyram as a foliar spray. It is open-access. Additional publications presenting data on experiments with both spray (Fluopyram) and injection (Thiabendazole/Arbotect) are in preparation.

I summarize briefly here their findings as of August 2024.

In all the trials, the scientists judged efficacy of treatments by counting the number of viable nematodes in leaves, viable nematodes in overwintering buds, and BLD symptom severity at appropriate times before and after treatment (spray or injection).

Tests of foliar sprays on small to medium sized trees

The first tests of foliar applications that resulted in BLD suppression were carried out in Ohio starting in 2021, then expanded to other field sites in Ohio and several states in New England in 2022 and 2023 seasons. In early trials, trees were sprayed four times starting in mid to late July at 21-day intervals. The scientists say that recent trials focus on application timing and rate. They hope that optimizing these factors will help generate new recommendations that are more sustainable while maintaining efficacy.

At the annual meeting of the American Phytopathological Society in July 2023, Bartlett announced that Fluopyram is an effective management tool to combat BLD – on smaller trees that can be treated using foliar application. There are several EPA-registered products, though only one, Broadform, has been so far been granted a section 2(EE) recommendation “For Control of Beech Leaf Disease on Beech Trees.”

Treatments are less effective in situations where the inoculum load is very high (for example, a very dense stand of infected trees); or where mature, untreated canopies hang over treated understory beech.

They suggest that managers focus treatments on high-value specimen beech, collection preservation, and potentially uncrowded mixed natural stands.

Treatments should be made by certified pesticide applicators who are familiar with the disease and treatment specifications. For the injection treatment, technical training and specialized equipment is needed. Bartlett arborists and plant health care specialists in locations affected by BLD have all been trained to perform the treatments, and some other arborists are doing BLD treatments as well using the same products.

Soil drench

Matt Borden said that they tested drenches with three different chemicals. The approach did not reduce nemtatode numbers sufficiently. However, as noted above, the Forest Service is funding additional tests exploring possible combinations of drenches with other actions, such as thinning. Discovering management options across a range of application methods (e.g., foliar, injection, drench) and modes of action is vital for a disease that covers such a broad range of locations and tree sizes and forms.

a macroinjection demonstration; photo by Matthew Borden via Flickr

Injections

Scientists injected Thiabendazole (TBZ) into beech on private land in three locations in Ohio and New Jersey. They tested two application rates and three application timings. They have two years of follow-up data for one site, one year for the others.

Key findings:

  • nematode numbers in buds in late winter consistently reflected foliar symptoms when the leaves opened.
  • Injections made before mid-July provided the greatest reduction in nemtatode numbers and best canopy improvement. Trees injected late in the season (30 August), after the nematode has begun dispersing from leaves to buds, exhibited some BLD symptoms the next year, but suffered less canopy dieback than controls.

Margery Daughtrey of Cornell said during a discussion of these finding that the trees’ persistence suggests that trees can tolerate some level of symptoms. Among other things, it might be possible to treat the trees less frequently than annually.

  • TBZ appears to provide at least two seasons of nematode suppression

Bartlett continues to monitor these trees to see how long the injected chemical suppresses nematode numbers and how long the tree remains healthy. They are also establishing new field sites to further optimize rate and timing.

TBZ – in a product called Arbotect 20-S – has been used to manage Dutch elm disease and sycamore anthracnose since the 1970s. However, it is also a well-known nematicide, previously used as an anti-parasitic drug in human and veterinary medicine. Once injected, TBZ protects the tree for more than one season. The injection technology (MACRO-Injection) has also been used for decades. It infuses the chemical directly into the tree’s vascular system; it does not rely on root uptake. Matt says injection does require take technical skill and the right equipment. To minimize the risk of the wound cracking and weeping, the injection should be done low on the side of the root flare, not on top.

While Arbotect 20-S has been registered for use in 48 states for many years, new labeling is required for its use in beech trees and against BLD. Special Local Needs labels, 24(C)s, have been granted by eight states – Connecticut, Massachusetts, Maine, New Jersey, New York, Pennsylvania, and Virginia. Registration in a ninth – Maryland – is in progress and Bartlett scientists are prepared to apply for several more. The problem is that only a limited number of these “special needs” labels may be issued, and BLD has expanded so far, and so rapidly, that it is already infesting beech in more states than may be covered by 24(C)s. Furthermore, 24(C) labels expire if not renewed. Most current 24(C)s will be active through 2028 – not ideal for a disease that will likely be with us long into the future. The product manufacturer (Syngenta) and distributor (Rainbow Ecoscience) are drafting a change to the main Arbotect 20-S label to add beech and the new nematode pest, but warn that EPA review and approval of amendments can take a very long time. Until then, we must resort to limited special local needs labels, and some states will miss out.

contrasting canopy transparency in beech treated with TBZ v. untreated controls; photo by Matthew Borden

One of the key scientists who developed these treatments for Dutch elm disease, R. Jay Stipes, professor emeritus at Virginia Tech, is quoted by Bartlett rejoicing that his work might help protect another tree species.

Matt believes the treatments will be effective if applied every 2-3 years. This approach would also spread out the cost – which will depend on the arborist but Dave Anderson of Rainbow Ecoscience estimated to be about $25 / inch of dbh.

It is always best to obtain an accurate diagnosis before treatment. The next step is talking through your options with a certified arborist or tree disease specialist. The “good” thing about BLD is that it is a progressive disease and will not kill a tree in a single year. Therefore, waiting until you know the disease is present or active locally is generally recommended.

Tree injection is better than foliar application where the latter is impractical (e.g., the tree is tall) or to reduce runoff, particularly near streams. Bartlett recommends treating any beech larger than 10 cm dbh by injection; smaller trees by foliar spray.

Treated trees should be sound, without serious decay, girdling roots, or other conditions that curtail uptake. Based on research results to date, they recommend treating the tree before mid-July. Bartlett is testing the results of injecting the shortly after full leaf expansion – early to mid-June. Bartlett scientists are testing several application rates to determine how long a single injection will suppress BLD. So far they have had good results from both low and moderate label rates (0.4-1.6 fl oz/inch DBH).

All the technical information re: research into treatments and recommendations for applying either the foliar or injection treatments has been provided by Dr. Matthew Borden of Bartlett Tree Research Laboratories. He can be reached at

mborden@Bartlett.com
https://www.bartlett.com/staff/matthew-borden-dpm

Dr. Borden says he is immensely grateful for the support that allows him and Dr. Loyd to travel widely to establish the BLD research sites and spend weeks collecting data each year with their team. Company founder Francis A. Bartlett established the Bartlett Tree Research Laboratories as a separate entity within the company, where capital is reinvested directly into stable, long-term support of scientific tree research and preservation. The model is well-suited to provide the flexibility and freedom needed to rapidly respond to emerging invasive species issues.


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 https://treeimprovement.tennessee.edu/

or

www.fadingforests.org

What I learned at the NPB meeting

The National Plant Board’s members are the lead plant health officials of the states and territories. Many federal officials also attend – from APHIS and DHS Bureau of Customs and Border Protection. Representatives of other North American phytosanitary entities participate – i.e., Canada, Mexico, and the North American Plant Protection Organization (NAPPO). Some stakeholder groups participate, especially the nursery industry. I have attended these meetings for over a decade because they provide an overview of pest issues and programs plus an unparalleled opportunity to network. The Nature Conservancy’s Leigh Greenwood also attends. We are the only representatives of the species conservation community to attend – others are missing great opportunities.

Here, I’ve listed 10 items that are among the most important the group discussed.

1) The funding situation for APHIS is worse than I realized

APHIS Administrator Mike Watson and Deputy Administrator (for plants) Mark Davidson both spoke about the need to cut programs to stay within the limits set by congressional appropriations. Funding for APHIS, as a whole, was cut only 1% for the current year (Fiscal Year 2024), cost-of-living salary increases mean less money for programs. (I believe Dr. Watson said $41 million less for FY24). If FY25 funding is the same, Congressionally mandated additional payraises will mean an another $20 million decrease in program funding.

Dr. Davidson said that the plant programs (Plant Protection and Quarantine) had been cut by 5% in FY24. However, Congress did not finalize the funding levels until about half-way through the fiscal year – so staying within the limits required even more severe cuts to programs in the remainder of FY24. To stay within these limits, APHIS cut several programs, among them a $3.6 million cut from the “tree and wood pest” program. This meant loss of funds to manage the polyphagous and Kuroshio shot hole borers, smaller cuts for programs managing Asian longhorned beetle and emerald ash borer, and perhaps the Asian flighted spongy moth. They anticipate additional cuts in these programs in FY25. The one bright light is the Section 7721 Plant Pest & Disease Management & Disaster Prevention Program. It provides steady funding for a range of plant health programs. The House version of the still-pending Farm Bill calls for increasing funding for this program by $15 million each year.

Nearly 100% ash trees in Oregon wetland — exposed to spreading EAB. Photo by Wyatt Williams, Oregon Department of Forestry

Remember this when I ask you to lobby for appropriations!  If we don’t advocate for funding the programs dealing with “our” pests, they will shrink.

Watkins and Davidson also worry that whoever is the next secretary of USDA might not support the agency when it seeks to withdraw funds to cover emergencies from the Commodity Credit Corporation – as Secretary Vilsack has.

APHIS and the DHS Customs and Border Protection (CBP) both praised a recent regulatory action that increases user fees for importers having goods cleared at ports. Kevin Harriger, CPB official in charge of agriculture programs, said the new funds would allow CBP to hire 700 new agricultural inspectors (currently there are 2,800 agricultural officials). That sounds great, but … when trade and passenger volumes crashed early in the COVID pandemic, things looked dicey for a while.  Plus – as I have argued repeatedly – real protection against pest introductions will come from stronger policies, not ramped-up inspections.

Pathologist Bruce Moltzan reported on the USFS Forest Health Protection program. He pointed out that the USFS has a very limited toolbox. In this fiscal year, the program has about $48 million, after salaries, to support its activities. Projects targetting insects receive 70% of the funding; those targetting pathogens 15%.

2) Invasive hornets

Washington State has not found any new nests of the Northern (formerly Asian) giant hornet (Vespa mandarinia). Miraculous!

However, Georgia detected another species, the yellow-legged hornet (Vespa velutina), near Savannah in August 2023. The Georgia Department of Agriculture, APHIS, and the University of Georgia are working to find nests – which are located at the top of tall pine trees in residential areas. Five nests were found in 2023; another four so far in 2024. Georgia hopes to place traps 100 miles out from each detection site. Like the northern hornet, V. velutina preys on honey bees. It was probably transported by ship or with its cargo.

A third species, V. tropica, has been introduced on Guam.

3) Better Federal-State Cooperation — Sometimes

APHIS and the state phytosanitary officials have set up structures –  e.g., Strategic Alliance/Strategic Initiative, or SASI – to work together more closely. CBP joins the coordinating meetings. One program described at the meeting is the effort to contain spread of the box tree moth (Cydalima perspectalis). This effort came out of discussions at last year’s Plant Board meeting, with follow-up gatherings of APHIS, the states, and the nursery industry. The moth is known to be present in New York, Massachusetts, Michigan, Ohio, and now Delaware – plus several Canadian provinces.

A second project concerns how much data to share about state detections of pests – which are recorded in the National Plant diagnostic Network database. These data have accrued over 20 years … and are sought by both other states and academic researchers. States are often reluctant to allow public review of detection data because they fear it will cause other states or private parties to avoid buying plants or other goods from the infested area. While the project team has not yet decided how to deal with these conflicts, they said they were more inclined to share “nonconsequential data” – meaning data on a pest everyone already knows is present, not a pest under regulation or a new detection. In other words, “consequential” seems to pertain to industry profits, not damage to agricultural or natural resources.

EAB-killed ash along Mattawoman Creek, Maryland. Photo by Leslie A. Brice

4) Update: 20 years of tackling the emerald ash borer

Craig Kellogg, APHIS’ chief plant health representative in Michigan, reviewed 20 years of dealing with the emerald ash borer (EAB). He is optimistic about the impact of the biocontrol agents that have now been released in 32 states and four provinces. The larval parasitoids are dispersing and EAB densities are coming down. He conceded that over-story and mature ash are still dying, but says ash in long-infested areas are regenerating well. Scientists agree (see Wilson et al. 2024; full citation at end of the blog). Woodpeckers are still the most effective biocontrol agent of EAB for over-story ash, especially in locations where introduced parasitoids are not established. So far, the growing numbers of biocontrol agents are still parasitizing too few EAB larvae to prevent decline of over-story ash trees.

5) Flighted Spongy Moths

APHIS reported on recent detections of flighted spongy moth from Asia on ships coming to U.S. ports. The program covers four closely related species of Lymantria. All have much broader host ranges than Lymantria dispar, plus the females are capable of sustained flight, so they spread more rapidly.

The principal strategy to prevent their introduction is to require ships that call at ports along the Pacific coast in Russia, China, Japan, and North and South Korea to ensure that the ships’ superstructures and cargo are clean. Before arriving at U.S. ports, the ship’s captain must inform CBP where it has called over the last 24 months. Then, CBP conducts an inspection. If CBP inspectors find a small number of egg masses, they remove the eggs and spray pesticide. If the inspectors detect a large number of egg masses, the ship is ordered to leave port, clean itself, and undergo re-inspection before it can return.

Four countries in the Americas – the U.S., Canada, Chile, and Argentina – and also New Zealand have very similar programs.

Detections follow natural changes in population levels in the exporting regions. APHIS’ program leader, Ingrid Asmundsson, reported on an unfortunate coincidence in 2014. A huge moth population outbreak occurred simultaneously with very low fuel prices in Russia. The latter attracted many ships to call there.  An even bigger population surge occurred in 2019. Asmundsson expects another high-moth period this year.

flighted spongy moths infesting a ship superstructure

APHIS is working on putting this program on a regulatory foundation; this would allow the agency to be more specific in its requirements and to impose penalties (other than expulsions from ports). I’ll let you know when the proposed rule is published for comment.

6) Regional Reports: Old Pests, New Pests

Representatives of the regional plant boards informed us of their “new pest” or other concerns.

Gary Fish, president of the Eastern Plant Board, mentioned

  • the need for additional research on management of beech leaf disease
  • concern about impact of box tree moth and vascular streak dieback on the nursery industry (the latter is a threat to dogwood and redbud)
  • spread of elm zig-zag sawfly in Vermont and Connecticut
  • awareness that laurel wilt is moving into Virginia and maybe farther north.
elm zig-zag sawfly; photo by Gyorgy Csoka via Bugwood

There was a more general discussion of beech leaf disease. What can be done, given that the disease is so widespread that no one is regulating movement of beech. Gary Fish advised outreach and efforts to reach agreement on management approaches. Chris Benemann, of Oregon, suggested informing other states so that they can decide whether to take regulatory action. A representative of CBP urged engaging stakeholders by asking for their help.

Chris Benemann, President of the Western Plant Board, expressed concern about APHIS’ reduced funding for spongy moth detection and control efforts. She also worries about the recently detected population of Phytophthora austrocedrii in an Oregon nursery. The western states are also focused on several longstanding pest problems – grasshoppers, Japanese beetle; and a new beetle from Australia that is attacking almonds, pistachios, and walnuts.

tree infested by hemlock woolly adelgid; photo by F.T. Campbell

Megan Abraham of Indiana reported that members of the Central Plant Board are concerned about

She noted that nursery stock is increasingly coming from more distant – and cheaper – producers, raising the risk of new pests being introduced.

Finally, Abraham expressed concern about decreased funding at the same time as the need is growing – and asked with whom states should collaborate in order to reverse this trend.

Kenny Naylor of Oklahoma, Vice President of the Southern Plant Board, concurred that funding levels are a major concern. He mentioned specifically the spongy moth Slow the Spread program and eradication of the Asian longhorned beetle outbreak in South Carolina. Another concern is the Georgia hornet outbreak.

7) Phasing Out Post-Entry Quarantine

APHIS and the NPB have agreed to phase out the post-entry quarantine (PEQ) program. A program review revealed several problems, some of which astound me. When examining plants in quarantine the scientists still relying on visual inspection! And they are looking for pests identified 45 years ago (1980)! While I think PEQ programs can be valuable in preventing introduction of disease agents, as implemented in recent decades it does not.  Twenty years ago, citrus longhorned beetles escaped from a “quarantine” area in a commercial nursery in Washington state. These Cerambycids are more than an inch long!

citrus longhorned beetle; photo by Art Wagner, USDA via Bugwood

Part of this phase-out is to transfer plant species harboring pests of concern to the Not Authorized for Importation Pending Pest Risk Assessment (NAPPRA). While the APHIS speaker said that NAPPRA allows the agency to act quickly when it detects evidence of pest risk, I have found lengthy delays. The third round of proposals was published in December 2019! The fourth round of species proposed for NAPPRA listing should be published soon; a fifth round is now in draft inside the agency.

8) Christmas Greens – Spreading Pests

Officials from Oregon, Maine, and Illinois described their concerns about pests being spread by shipments of various forest or plant products, especially Christmas greens. Mentioned were spongy moths, link hemlock woolly adelgid, link elongate hemlock scale, balsam woolly adelgid, link and box wood moth. Part of the challenge is that the vectoring items are often sold by unregulated outlets – multiple stores, Christmas tree lots – and through on-line or catalog outlets. There are also extreme demands on the regulatory enforcement staff during the brief holiday sales season. Several states are unsure whether they have authority over decorative products – although others pointed out that they are regulating the pest, regardless of the object for sale or type of store.

9) Pests in Firewood

Leigh Greenwood of The Nature Conservancy noted that the state agencies that issue firewood regulations – often the plant protection organization (state department of agriculture) — do a good job alerting the public about the risks and rules. However, the public looks first to state parks agencies for information about camping – and those agencies have less robust educational efforts. It is important to put the message where the public can find it when they don’t know it exists – before they include firewood from home in their camping gear.

10) Projects of the North American Plant Protection Organization

The North American Plant Protection Organization (NAPPO) is working on several projects of interest to those of us concerned about tree-killing pests. One project is evaluating risks associated with wood products, especially how well one international regulation, ISPM#15 is working for dunnage. Another projects is testing the efficacy of the heat treatment specified by ISPM#15 (50o C for 30 minutes). A third project — almost completed – is evaluating fumigants that can be alternatives to methyl bromide.

In conclusion, each annual meeting of the National Plant Board is packed with new information, updates on current pests, and comments on by the state agencies who suggest new approached to APHIS and hold the agency to account. It is well worth attending. Information about upcoming meetings of both the national and four regional plant boards is posted on the NPB website, https://www.nationalplantboard.org/

Signatories to the APHIS-NPB strategic alliance

SOURCE

Wilson, C.J., T.R. Petrice, T.M. Poland, and D.G. McCullough. 2024. Tree species richness and ash density have variable effects on emerald ash borer biological control by woodpeckers & parasitoid wasps in post-invasion white ash stands. Environmental Entomology.

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  https://treeimprovement.tennessee.edu/

or

www.fadingforests.org

APHIS Annual Report Describes Helpful Programs … Since Cut Back Because of Funding Shortfalls

Flighted spongy moths infesting a ship’s superstructure

USDA’s Animal and Plant Health Inspection Service (APHIS) has issued its annual report for Fiscal Year 2023.  The report is part of an enhanced outreach effort that I believe is an effort to persuade the Congress to provide additional funds. However, as I describe below, at this summer’s annual meeting of the National Plant Board, link APHIS’ leadership stated that funding shortfalls are forcing them to curtail many programs. These include ones important to those of us concerned about threats to North American trees. I applaud this action and hope it succeeds!

The report contains some good news but I consider the overall approach depressing. Tree-killing pests continue to receive little attention. The report also emphasizes APHIS’ efforts to facilitate export of agricultural products – an understandable stance given American politics.

The opening summarizes the agency’s activities includes:

  • Examples of programs targetting pests abroad, before they can reach the U.S. All are fresh fruits and vegetables;
  • APHIS or  staff at U.S. borders:
    • Approved (cleared) 27,235 shipmentscontaining over 1.87 billion plant units (e.g., a single plant or cutting, or vial of tissue culture plantlets) and 670,811 kilograms of seeds. They intercepted 2,176 quarantine pests. (APHIS carry out these inspections at Plant Inspection Stations – separate from the port environment where DHS Customs and Border Protection (CBP) staff inspects other cargo.)
  • Identified approximately 92,000 pestsfound during CBP inspections of cargo, mail, and express carrier shipments and took quick action to prevent those of concern from entering the U.S.
  • Facilitated entry of regulated agricultural cargo by monitoring more than 62,000 treatments of various kinds, that is, fumigations, cold or heat treatments, and irradiation.
  • Examples of APHIS’ efforts to slow pests’ spread within the country cited plant pest surveys — with coordinated responses — for approximately 45 pests. Also APHIS described funding to help citrus growers combat citrus greening.
  • The report has separate subreports on the following programs: risk analysis, pest detection, “specialty crop” pests, and tree and wood pests. The last two contain information specific to our interests.

Tree and Wood Pests

This program protects forests, private working lands, and natural resources. It targets specific pests: the Asian longhorned beetle, emerald ash borer, spongy moth, and most recently the invasive shot hole borers. The report notes that numerous native, widespread hardwood tree species are vulnerable to these pests. APHIS asserts an economic justification for the program: conserving forests enhances rural communities’ economic vitality, supports forest-related industries, and maintains the ecosystem services provided by urban trees.

Unfortunately, at this summer’s annual meeting of the National Plant Board APHIS leadership said funding shortfalls forced them to pull back on all these programs.

Programs as Described in the Report

Asian Longhorned Beetle  

ALB eradication aims to protect the 30% of U.S. trees that are ALB hosts. These trees support multi-billion-dollar maple syrup, timber, tree nursery, trade, and tourism industries. After reviewing the history of ALB detections, starting in Brooklyn in August 1996, the report describes APHIS’ eradication strategy as comprising surveys, regulatory inspections and quarantine restrictions, removal of infested and high-risk trees, and chemical treatment applications. In FY 2023, the program surveyed more than 763,000 trees across the four regulated areas: New York, Massachusetts, Ohio, and South Carolina. Each program is summarized.

Good news at two locations. On Long Island: only 11 new infested trees were found after a survey of 43,480 trees. In Worcester County, Massachusetts, no new infested trees were found after surveying nearly 360,000 trees. However, in Tate Township, Ohio, surveys detected 163 new infested trees. And in

South Carolina, the program is at an earlier stage — surveying a portion of the quarantine area. The program surveyed nearly 140,000 trees and removed 1,700 in FY 2023.

At the National Plant Board Meeting, Deputy Administrator Mark Davidson explained that the FY2024 appropriation cut $3.6 million from the “tree and wood pests” account. This required the agency to reduce funding for the ALB eradication program.

Emerald Ash Borer

The report summarizes the spread of EAB since its first detection in 2002 in Michigan to 37 states and the District of Columbia (APHIS does not mention EAB’s presence in five Canadian provinces.)

Saying that EAB has spread beyond what a regulatory program can control, the report notes that APHIS ended the regulatory program in FY 2021. In FY 2023 the agency continued the transition to a program relying primarily on biocontrol. In FY2023, APHIS provided parasitoids to 155 release sites – three in Canada, the rest in 122 counties in 25 states. APHIS and cooperators continue to assess their impacts on EAB populations and tree health at release sites and nearby areas. Field evaluations indicate the EAB parasitoid wasps and other EAB natural enemies (woodpeckers) are protecting regenerating sapling ash from EAB.

At the National Plant Board Meeting, Deputy Administrator Mark Davidson explained that the FY2024 appropriation cut $3.6 million from the “tree and wood pests” account. This required the agency to reduce funding for the EAB containment program – probably the biocontrol component.

Spongy Moths

Spongy moths (the species formerly called European gypsy moths) are established in all or parts of 20 eastern and midwestern states, plus the District of Columbia. APHIS and state cooperators regulate activities in the quarantine area to prevent the moths’ human-assisted spread to non-quarantine (non-infested) areas – primarily West coast states. To address the moths’ natural spread, APHIS PPQ monitors the 1,200-mile-long border of the quarantine area and adds newly infested areas to the regulated area. The USDA Forest Service – APHIS – Slow-the-Spread Foundation program has greatly reduced the moth’s rate of spread and has eradicated isolated populations.

Another component of the program aims to prevent introduction of members of the flighted spongy moth complex link from Asia. The Asian species have broader host ranges and the females can fly, so they could spread faster. A multi-nation cooperative program is designed to prevent the moths’ hitchhike on vessels coming from Asia. link APHIS supports this program through negotiations and support of CBP’s offshore vessel inspection, certification, and cleaning requirements. Canada participates in the same program.  

In FY 2023, APHIS and state cooperators continued efforts to delimit possibly introductions in Washington State (no additional moths detected); and California and Oregon (initial detections in FY 2020).

At the National Plant Board Meeting, Deputy Administrator Mark Davidson explained that the FY2024 appropriation cut $3.6 million from the “tree and wood pests” account. This required the agency to reduce funding for the flighted spongy moth program.

California sycamore infested by polyphagous shot hole borer; photo by Beatriz Nobua-Behrmann UC Cooperative Extension

Shot Hole Borers

The report notes that various non-native shot hole borers have been detected in several states. Their hosts include trees in forests and urban landscapes, tea plantations, and avocado orchards. The program’s focus was apparently on the polyphagous and Kuroshio shot hole borers devastating riparian habitats in southern California and urban areas in other parts of California. At California’s request, APHIS and the USDA Forest Service helped establish a working group, led by USFS, with the goal of strategically addressing both shot hole borers in California. In FY 2023, APHIS’ helped with foreign explorations for possible biocontrol agents, as well as host specificity testing.

APHIS leadership told the National Plant Board in July 2024 that it had dropped this entire program due to funding shortfalls.

Specialty Crop Pests

While much of this report concerns pests of agricultural crops (e.g., grapes, citrus, potatoes), it also summarized efforts re: Phytophthora ramorum (sudden oak death) and spotted lanternfly. APHIS says its efforts protected nursery stock production worth approximately $1.3 billion as of 2019, and tree fruit production worth approximately $1.7 billion in 2021.

map showing areas of the Eastern United States at risk to P. ramorum – developed by Gilligan of Cambridge University

Phytophthora ramorum

The report states that APHIS seeks to limit P. ramorum’s spread from affected nurseries. The agency does this via regulatory strategies. During FY 2023, 16 nurseries were governed by more stringent rules  under the federal program which are imposed on nurseries that have been determined in past years to harbor P. ramorum-infected plants.

In addition, Oregon officials continued surveys of an area outside its quarantine zone because of a detection the previous year. APHIS will adjust the federal quarantine depending on the state’s findings.

The APHIS report does not discuss several pertinent events that occurred in FY2023. [For more details, read the California Oak Mortality Task Force newsletters for 2023 – posted here.

First, APHIS does not mention or discuss the implications of detection of two new strains of P. ramorum — EU1 & NA2 — in west coast forests. The presence of EU1 in a new California county (Del Norte) was confirmed in Feb 2023.

Second, the report said that Oregon is trying to determine the extent of the P. ramorum infection detected outside the state’s quarantine zone. However, it does not mention that this outbreak involves the new NA2 lineage – and that NA2 was known to be present in nurseries in the region since 2005.

The report also does not clarify that three nurseries to added to the more stringent program were so treated because SOD-infected plants were found on their premises.

Nor does the report note that at least two new naturally-infected hosts of P. ramorum were identified:  Western sword fern (Polystichum munitum) and Arbutus x ‘Marina’.Koch’s postulates need to be completed on the latter so it has not yet been added to APHIS’ official host list.

Spotted Lanternfly

Spotted Lanternfly (SLF) was found in 16 states in FY 2023. APHIS’ program enjoyed funding provided through Specialty Crop Pests and from the Plant Protection Act’s Section 7721 link ($6 million from the latter).

The report notes that APHIS still does not have enough data to determine SLF’s impacts on agriculture. Thus far, vineyards have been the most adversely affected agricultural segment, mostly due to SLF acting as a stressor to vines. Also, the sticky, sugary “honeydew” produced by SLF attracts other insects and promotes sooty mold growth. These can ruin the fruit and further damage the plant.

SLF populations are strongly linked to major transportation pathways, such as railroads and interstate highways. APHIS targets treatments and, in some areas, removes SLF’s preferred host plant (tree of heaven [Ailanthus]), from transportation hubs. The aim is to reduce the risk of SLF’ spread to new areas and to eradicate isolated infestations. In FY 2023, APHIS and cooperators treated 4,637 properties covering 6,455 acres in affected areas. However, during the National Plant Board meeting both state and APHIS officials complained to me that managers of these transportation hubs raise many barriers to their access, sharply limiting the program’s chance of success.

Ailanthus altissima – drive of spotted lanternfly invasion

The program was expanded after National Environmental Policy Act-mandated environmental review. This allowed APHIS to conduct treatments in four additional states—Indiana, Massachusetts, Michigan, and Rhode Island. In addition, program cooperators identified three potential biological control organisms, one that targets the tree of heaven and two that target SLF. APHIS will continue to evaluate them and develop methods to rear them in the laboratory.

Finally, in fiscal year 2023, APHIS joined the National Association of State Departments of Agriculture and the National Plant Board to develop a national strategic plan outlining the future direction of the SLF program. With the strategic plan, PPQ aims to harmonize the approach across states to slow SLF’s spread, develop consistent outreach messaging for a nationwide audience, and more effectively use existing state and Federal resources. Continued spread of SLF despite the huge effort, rising costs of the program, and new scientific findings spurred reconsideration of the strategy.

To summarize, I hope that APHIS’ annual report will – in the future – help members of Congress and their staff understand the agency’s programs’ purpose and past successes. This increased understanding might make it easier to advocate for more funding. I am troubled, however, by the agency’s glossing over significant problems.  

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  https://treeimprovement.tennessee.edu/

or

www.fadingforests.org

Two new Phytophthora arrivals (plus another looming) in U.S. forests & nurseries

Breeding Port-Orford cedar for resistance to Phytophthora lateralis; photo by Richard Sniezko, USDA Forest Service

At the annual meeting of the National Plant Board in July, I learned that two new Phytophthora species have been detected in the United States. Questions remain about how each arrived.

  1. Phytophthora austrocedrii

This species was detected in a nursery in Oregon, then traced back to a supplier in Ohio. Officials are trying to determine how it entered the country – and then spread.

junipers in Great Britain killed by P. austrocedri; Forestry Research

In the United Kingdom, P. austrocedri has killed trees in the Juniperus and Cupressus genera. Damage is particularly significant at two sites in northern Scotland and in England’s Lake District. The principal host, Juniperus communis, is an important native species. It is already considered vulnerable. P. austrocedri has also been detected in Argentina, where it is killing the native Chilean or Patagonian cedar (Austrocedrus chilendris). The cedar species is the only one in the genus. Evidence indicates the pathogen was introduced to both Britain and Argentina; but its origin is unknown. Indeed, the species was first isolated by scientists as an unknown Phytopthora taxon on a juniper in an import/export nursery in Germany. All reported hosts are members of the Cupressaceae family (UK forest research website).

Of greater concern to Americans, P. austrocedri has also infected individual trees of Port-Orford cedar (Chamaecyparis lawsoniana). (UK forest research website).  

Port-Orford cedar is a species endemic to a small range in southwestern Oregon and Northwestern California.

POC populations have been severely reduced over the past century by a different non-native Phytophthora, P. lawsonii. US Forest Service scientists recently announced that they have bred trees resistant to this pathogen – and offered seedlings for widespread planting.

Possible hosts in the Pacific Northwest – other than Port Orford cedar – include Juniperus californica, Juniperus grandis, Juniperus occidentalis, and Juniperus maritima – although the junipers might be limited to arid environments, where they would presumably be less vulnerable. https://plants.usda.gov/home/classification/15147

Research in Great Britain shows that P. austrocedri spreads in water and by movement of infected plants and contaminated soil. Footwear, camping equipment, and vehicle tires can all carry the pathogen. This makes the pathogen particularly difficult to control (this is another similarity with P. lawsonii).

  • Phytophthora abietivora  

P. abietivora was originally found on a diseased Christmas tree (Fraser fir, Abies fraseri) in Connecticut in 2019. It has since been reported in Pennsylvania and Virginia; and in forest nurseries and Christmas tree plantations in Quebec and Ontario. The Canadians report that it has not caused disease (Canadian website). However, the Canadian representative at the National Plant Board meeting expressed concern and asked USDA APHIS to clarify what actions it is taking regarding this species.

(Natural populations of Fraser fir have been severely reduced over the past century by the balsam woolly adelgid.)   

Fraser fir killed by balsam woolly adelgid; Clingman’s Dome, Great Smoky Mountains National Park

Several additional hosts have been identified, including balsam fir (Abies balsamea) and eastern hemlock (Tsuga canadensis); and deciduous or hardwood species: hickory (Carya sp.), flowering dogwood (Cornus florida), American witch hazel (Hamamelis virginiana), mountain holly (Ilex montana), red maple (Acer rubrum), silver birch (Betula lenta), American beech (Fagus grandifolia); and several oaks: white (Quercus alba), chestnut (Q. montana) and northern red oak (Q. rubra) (Canadian fact sheet).

According to the Canadian website, P. abietivora causes root rot and subsequent foliar chlorosis, discoloration, stem cankers, and sometimes tree decline and death. Determining which Phytophthora species is the causal agent of a tree’s symptoms requires laboratory testing. The Canadian fact sheet reports that wet, cool conditions provide ideal environments for P. abietivora. Like other Phytophthora species, P. abietivora can be spread through soil and water, as well as via infected plant material or pots or trays (particularly if soil remains on the equipment). The Canadian fact sheet has several photographs illustrating symptoms and additional sources.

Liriodendron tulipifera; photo by Evelyn Simak via Geograph

  • Phytophthora kernoviae 

P. kernoviae was first detected in southwestern England in 2003. link In England, this pathogen has caused significant diseases in native Fagus sylvatica (European beech) and lesions on trunks of a European oak, Quercus robur. More worrying are the trunk lesions on the North American native yellow or tulip poplar (Liriodendron tulipifera) and lesions on foliage of Monterey pine (Pinus radiate), giant sequoia(Sequoiadendron giganteum), and several North American native shrubs, Rhododendron macrophyllum (Pacific rhododendron), R. occidentale (western rhododendron), R. catawbiense (Catawba rosebay) and Umbellularia californica (California bay laurel).

Phytophthora kernoviae on R. ponticum in Cornwall

The infestation in Cornwall is sustained by heavy sporulation on the non-native shrub Rhododendron ponticum, which is invasive in woodlands. Worrying for Americans is the fact that P. kernoviae sporulates on three plant species native to West coast forests — Rhododendron macrophyllum, R. occidentale, and Umbellularia californica – as well as on R. catawbiense, which is native to the southern Appalachians.

USDA APHIS requested adoption of a “response plan” targetting P. kernoviae under the National Plant Disease Recovery System (NPDRS). This plan was adopted in 2008 and updated in 2015.

The recovery plans found the areas at highest risk are eastern slopes of the Appalachian Mountains because this area combines a native sporulating host and residential landscaping choices that are likely to include hosts that could transport the pathogen. A lower risk was identified for West Coast forests.

Because of this status, P. kernoviae is also a “priority” pest for surveys under the Cooperative Agricultural Pest Survey (CAPS) program. According to Purdue University’s “pest tracker” website four states have reported carrying out surveys for P. kernoviae in one or more years since 2016: Oregon, Tennessee, Pennsylvania, and Virginia. Surveys in Oregon were carried out in 2018 – 2020. In 2020 the counties surveyed included Curry County, where three strains of P. ramorum link have become established. The Purdue list is not certified as accurate or complete. To date, no surveys have detected P. kernoviae in the United States or – I believe – in Canada.

SOURCES

Canadian fact sheet at https://inspection.canada.ca/en/plant-health/invasive-species/plant-diseases/p-abietivora/fact-sheet; accessed July 2024

Canadian website at https://inspection.canada.ca/en/plant-health/invasive-species/plant-diseases/p-abietivora  accessed July 2024

Purdue University’s “pest tracker” website at pesttracker.org. Survey Status of Phytophthora leaf blight – Phytophthora kernoviae . (2023)  accessed July 2024

UK research website at https://www.forestresearch.gov.uk/tools-and-resources/fthr/pest-and-disease-resources/phytophthora-austrocedri-disease-of-juniper-and-cypress/  accessed July 2024

For details on existence of two clonal lineages of Phytophthora austrocedrii, see Henricot, B. A. Perez-Sierra, A.C. Armstrong, P.M. Sharp, and S. Green. Phytopathology 2017. 107:12, 1532-1540.

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  https://treeimprovement.tennessee.edu/

or

www.fadingforests.org

Congress is considering the Farm Bill – help improve it!!!

Senator Peter Welch of Vermont

The House and Senate Agriculture committees are edging toward adopting the next Farm Bill, which   is a year past due. Farm bills set policy, funding levels, and more, for 5 years. Each covers a wide range of subjects, including crop subsidies and insurance; food stamps; rural development (including wifi access); forestry policy; and research.

As you might remember, CISP aims to improve USDA’s programs — not only to prevent introductions of non-native tree killing pests and pathogens but also to better respond to those that enter the US and become established. I summarize here what the Senate and House bills have in common and how they differ on these issues.

I understand that the minorities, that is, House Democrats and Senate Republicans, have not accepted all aspects of the majorities’ drafts. So let’s take the opportunity to ask for better bills.

Both the House and Senate bills would “simplify” the USDA Forest Service’s obligations to prepare environmental assessments under the National Environmental Policy Act (NEPA). I have not analyzed which bill weakens NEPA more.

The Senate Bill: The Rural Prosperity and Food Security Act of 2024

The Senate bill addresses forest pest species in several places: Title II — Conservation, Title VII — Research, and Title VIII — Forestry. Here, I describe relevant sections, beginning with the section that partially addresses CISP’s proposal.  

Title VIII — Forestry. Section 8214 requires the USDA Secretary to establish a national policy to counter threats posed by invasive species to tree species and forest ecosystems and identify areas for interagency cooperation.

This mandate falls far short of what we sought in a previous bill (S. 1238). However, depending on the exact wording of the bill and accompanying report, perhaps we can succeed in building a stronger program.

It is most important to obtain funding for applied, directed research into resistance breeding strategies, “bulking up,” and planting seedlings that show promise. Please contact your senators and ask them to work with the sponsors – Peter Welch [D-VT], Maggie Hassan [D-NH], and Mike Braun [R-IN] – to try to incorporate more of S. 1238 in the final bill.

The Senate bill contains other provisions that might be helpful for invasive species management – although not part of what CISP and our partners asked for.

‘ōhi‘a trees killed by rapid ‘ōhi‘a death; photo by Richard sniezko, USFS

Title VIII — Forestry. In Section 8506, the Senate bill would require that the US Departments of Agriculture and Interior continue working with Hawai`i to address the pathogen that causes rapid ‘ōhi‘a death. The section authorizes $5 million for each of the coming five fiscal years to do this work. Unfortunately, authorization does not equal funding. Only the Senate and House Appropriations Committees can make this funding available. Hawai`i’s endemic ‘ōhi‘a trees certainly face a dire threat. CISP is already advocating for funding to support resistance breeding and other necessary work.

Title VIII — Forestry. Sections 8247 and 8248 support USDA Forest Service’s nursery and tree establishment programs. My hesitation in fully supporting these provisions is that I fear the urge to plant lots of trees in a hurry will divert attention for the need to learn how to propagate many of the hardwood tree species that have been decimated by non-native pests. However, I agree that the U.S. lacks sufficient nursery capacity to provide anything close to the number of seedlings sought. Perhaps this program can be adjusted to assist the “planting out” component of our request.

Title VII — Research. Section 7208 designates several high-priority research initiatives. On this list are spotted lanternfly, and “invasive species”.  A number of forest corporations have been urging Members of Congress to upgrade research on this broad category, which I believe might focus more on invasive plants than the insects and pathogens on which CISP focuses. How the two ideas are integrated will be very important.

Another high-priority initiative concerns the perceived crisis in failed white oak regeneration.

Title VII — Research.  Section 7213 mandates creation of four new Centers of Excellence at 1890 Institutions. These are historically Black universities that are also land-grant institutions]. These centers will focus on: 1) climate change, 2) forestry resilience and conservation; 3) food safety, bioprocessing, and value-added agriculture; and, 3) food and agricultural sciences and the social sciences.

Title II — Conservation. Section 2407 provides mandatory funding (which is not subject to annual appropriations) of $75 million per year to the national feral swine eradication/control program (run by USDA APHIS’ Wildlife Service Division). I discuss this program in a separate blog.

The Senate bill also mandates use of several conservation and other programs to address the causes and impacts of climate change. This requirement is directly countered by the House Agriculture Committee’s bill (see below).

The House Bill

Title VIII — Forestry. This section contains none of the provisions CISP’ sought to  USDA’s management of tree-killing non-native insects and diseases.

Instead, the House bill calls on the USFS to establish a comprehensive approach to addressing the demise of the giant sequoia trees.

Title VII — Research The House bill, like the Senate’s, lists the invasive species and white oak research initiatives as high priority. The House, unlike the Senate, does not include spotted lanternfly.

Title II — Conservation. As I noted above, the House bill explicitly rescinds all unobligated conservation funding from the Inflation Reduction Act. It reallocates these funds to the traditional conservation programs, e.g., the Environmental Quality Incentive Program and Watershed Protection and Flood Prevention. The bill would use these funds to support “orphan” programs – naming specifically the national feral swine eradication/control program. The House bill provides $150 million – apparently across the five years covered by the Farm Bill, so $30 million per year.  Finally, the House allocates 60% of the hog management funds to APHIS, 40% to the Natural Resources Conservation Service.

spotted lanternfly – target of at least 11 projects funded through APHIS’ the Plant Pest and Disease Management and Disaster Prevention Program in FY24. Photo by Holly Raguza, Pennsylvania Department of Agriuculture

Title X —Horticulture, Marketing, and Regulatory Reform. The House’s summary says it is taking steps to protect plant health. It does this by increasing funding for the grant program under the Plant Pest and Disease Management and Disaster Prevention Program – §7721 of the last (2018) Farm Bill. The increase would raise the amount of money available each year from the current level of $70 million to $90 million. These funds are mandatory; they are not subject to annual appropriations. Research, development, and outreach projects funded by this program have certainly added to our understanding of plant pests, hence to their effective management. However, they are usually short-term projects. Therefore they are not suitable for the long-term commitment required for resistance breeding programs. See here  and here.  

Title III — Trade. Here, the House bill exacerbates the current imbalance between trade promotion and phytosanitary protection. The bill doubles the authorized funding for USDA’s Market Access and Foreign Market Development programs. I concede that this measure probably does reflect a bipartisan consensus in the Congress to support robust programs for promoting agricultural exports.

Also under this Title, the House bill requires the USDA Secretary to conduct regular assessments to identify risks to critical infrastructure that supports food and agriculture sector. This might be helpful – although it is not clear that this assessment would include to threats to forest or urban trees not used commercially (e.g., for timber).

At a recent forum on biological control sponsored by the National Association of State Foresters (NASF), it was reported that participants noted several problems: insufficient funding, significant delays in refilling positions, inadequate research capacity, lack of brick-and-mortar infrastructure, and declining college enrollments in biocontrol-related studies. The NASF Forest Science Health Committee is developing a “Statement of Needs” document that NASF and others can use to lobby for funding to fill these gaps. I hope you will join them in doing so!

salt cedar (Tamarix sp.) attacked by biocontrol agent; photo by J.N. Stuart via Flickr

However, as I note above, empowering resistance breeding programs requires a long-term commitment, that is, a comprehensive alteration of policies and infrastructure – beyond annual appropriations.

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

or

www.fadingforests.org

Feral pigs – 20 years of APHIS engagement

feral hogs in state wildlife area, Florida; photo by Craig Oneal via Flickr

Most invasive species detection and control programs suffer from inadequate funding. Feral hogs (Sus scrofa) are the exception. True, feral hogs are widely considered among the most damaging of invasive species. They are conspicuous. And they cause damage to agricultural crops – thus energizing a politically powerful constituency. (The extent of that damage is open to question; see my discussion below.) Can we learn from the political success of this program to build support for countering other invasive species?

[Several forest pests are also listed as among the “100 worst” invasive species: Asian longhorned beetle, chestnut blight, gypsy or spongy moths, Dutch elm disease, Phytopthora cinnamomi. Many invasive plant species present in the United States are also listed. These bioinvaders have not elicited the same level of response.]

According to a US Department of Agriculture report (USDA 2018), feral hogs only recently spread throughout the United States. In 1982, they were thought to inhabit only a small percentage of counties in 17 states. As of 2018, they were recognized as present in ~ 43% of all counties in the country; those counties were in 38 states and three US territories. USDA APHIS lists the following impacts from feral hog activities: damage to crops (including tree seedlings), livestock pastures and feed supplies, other kinds of property, and natural resources. In addition, feral pigs might transmit disease to the human food supply and possibly to livestock, and occasionally threaten public safety. In response, APHIS proposed to develop a national response. The goal was to reduce the risks and damages and encourage better coordination among the states and with Canada and Mexico. Since environmental conditions and laws vary among states, APHIS provides resources and expertise while allowing operational flexibility. The early focus was on primarily northern states where eradication was considered viable. By 2019, Idaho, Iowa, Maine, New Jersey, and New York had been declared “pig free”.

The Feral Swine Eradication and Control Pilot Program was officially established as by the 2018 Farm Bill. It was funded at $75 million over the five-year life of the 2018 Farm Bill – or ~$15 million per year. The program is implemented jointly by USDA Natural Resources Conservation Service (NRCS) and APHIS. According to the website, USDA focused these efforts where feral swine pose the highest threat.

APHIS has published a report covering the initial 2014 – 2018 program. I expect they will shortly publish a report covering 2018- 2023. My quick review of the available but outdated report shows that nearly all the pig removal projects funded by the program aimed to protect property, particularly agriculture. Protection of natural resources benefited from far fewer projects. The states funding natural resource  projects most generously were Washington (92% of projects!); Illinois (62%); Nevada (48%); Florida (47%); Idaho and Missouri (both at 44%); Wisconsin and New Hampshire (both at 41%); Ohio (35%); Utah (34%); and Arizona (32%). Some of the Western states have considerable land managed by federal agencies; this might explain their relative focus on natural resources. Pennsylvania allocated only 1% of its projects to protecting natural resources. West Virginia and the U.S. Virgin Islands allocated none. I hope this tilt lessens in more recent years – although the program will clearly always be focused on agriculture.

There were no programs in five states: Massachusetts, Montana, Nebraska, South Dakota, and Wyoming.

Note that the summary of the draft Senate Farm Bill says this program would be funded at $75 million per year in future. This would increase funding 15 fold. I think this is probably a mistake in writing the summary; that the total funding would continue to be $75 million over five years.

I also reviewed the annual report issued by the APHIS Wildlife Services program’s National Wildlife Research Center (NWRC). The Center lists 17 publications by NWRC staff and cooperators dealing with various aspects of feral pig management [other than swine fever transmission]. Topics included feral pigs’ social structure; factors that influence reproductive rates; factors that influence efficacy of bait/trap programs; in-field methods to determine animal’s weight; and the extent to which hunters, farmers and the public accept various control techniques.

feral hog damage in a corn field; photo by Craig Hicks, USDA APHIS

Two of the studies – Didero et al. and VerCauteren et al. – aim to answer a fundamental economic question of feral hog management: how to determine the level of damage feral hogs cause to agricultural crops. Interestingly, authors of both studies conclude that existing data do not allow that determination. According to VerCauteren et al., understanding of wild pig damage is limited largely to one kind of damage — rooting – as it affects some natural resources (e.g., wetlands), some crops (e.g., grains, nuts, and beans), and some property (e.g., golf courses and cemeteries). They found few reports documenting damage from other behaviors or effects on pasture, livestock, sensitive species, public recreation spaces, and historical sites. Furthermore, they could not generalize the findings of even those studies that attempt to link the level of damage to pig population density. This is because these studies use many different metrics. They say that designing studies to capture the full scope of damage even in a local area will be complex because of the variety of resources at risk and of mechanisms by which damage might occur (e.g., rooting, consuming plants or animals, wallowing …). VerCauteren et al. suggest specific approaches that should be applied in future studies so that economic estimates will be consistent, shareable, and repeatable. I encourage you to read the articles to learn details of what is known about feral hog damage.  

I rejoice that one set of NWRS studies focuses on Missouri.  As I have blogged previously, Missouri has operated an aggressive program since the 1990s. I appreciate that APHIS is trying to learn how Missouri officials determined which approaches work best, and built support for the program among farmers, landowners, hunters, etc.

NWRC staff and cooperators also studied some other issues relating to invasive species impacts.  One study sought to predict the level of suppression of brown treesnakes that must be achieved to protect birds that might be reintroduced on Guam. A second study sought to find out whether invasive coqui frogs can survive in the colder climates of high elevations in Hawai`i. There is concern that the frogs might compete with native birds for food.  

SOURCES

Didero, N.M., K.H. Ernst, S.C. McKee, and S.A. Shwiff. 2023. A call and suggested criteria for standardizing economic estimates of wild pig damage. Crop Protection 165:106149. doi: 10.1016/j.cropro.2022.106149

United States Department of Agriculture National Feral Swine Damage Management Program Five Year Report FY14 – FY18

United States Department of Agriculture Animal and Plant Health Inspection Service Wildlife Services. 2024. Innovative Solutions to Human Wildlife Conflicts. National Wildlife Research Center Accomplishments, 2023.

VerCauteren, K.C., K.M. Pepin, S.M. Cook, S. McKee, A. Pagels, K.J. Kohen, I.A. Messer, M.P. Glow,  N.P. Snow. 2024. What is known, unknown, and needed to be known about damage caused by wild pigs. Biol Invasions (2024) 26:1313–1325          https://doi.org/10.1007/s10530-024-03263-z

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

or

www.fadingforests.org

Disappearing Floristic Diversity – Should Some of the Attention to Extinctions be Refocused on Invasive Plants?

Sakhalin knotweed (Fallopia (Reynoutria) sachalinensis) – an invasive plant widespread in Europe; photo by Katrin Schneider [korina.info] via Wikimedia

There is growing evidence that invasive plants – as distinct from invasive species of animals, microbes, etc. – play a significant role in causing the loss of floristic uniqueness at the local or regional level. I provide full citations of all sources at the end of this blog.

Less Diversity. More Similarity

Several studies show that plant invasions have a bigger impact than extinction in the homogenization of Earth’s flora. A major driver is sheer numbers. Daru et al. point out that 10,138 plant species have become naturalized to a region outside their native ranges while only 1,065 species have gone extinct. Even under a scenario in which all species currently included in IUCN Red List as “threatened” become extinct, non-native plant species naturalizations are by far the stronger contributor to biotic reorganization.

Winter et al. report that in Europe since AD 1500, plant invasions have greatly exceeded extinctions, resulting in increased taxonomic diversity (i.e., species richness) on the Continent but increased taxonomic and phylogenetic similarity among European regions. In other words, floras of individual European countries became phylogenetically and taxonomically impoverished. This situation is likely to worsen in the future because introductions continue.

Winter et al. conclude, more broadly, that a focus on species richness can be misleading because it does not capture the important effects of taxonomic or phylogenetic distinctiveness.

Yang et al. (2021) considered the situation globally. They divided most of Earth’s ice-free land surface into 658 regions. They found that introduction of non-native plants has increased the taxonomic similarity between any two of these regions in 90.7% of the time. Introductions increased phylogenetic similarity in 77.2% of those pairs. Australasia illustrates the situation. The region has a large proportion of endemic species, reflecting its unique evolutionary history and exhibiting high floristic diversity. However, the region has also received large numbers of non-native plants from other regions. The result is that the Australasian flora has lost much of its original uniqueness.

rubbervine (Cryptostegia madagascariensis) – one of the worst invasive plants in Australia; photo by Tatters via Flickr

Introduced plant species rarely cause outright extinction of members of the native flora of the receiving ecosystem – at least at the scale of a continent. Winter et al. found that in Europe, extinction usually occurs to plant species with small numbers that are limited to localized habitats. Often, however, the same species continue to thrive elsewhere on the continent. The “losing” country finds its flora becoming more similar to that of other European countries. It loses some uniqueness because it lost one or more components of its flora. However, for Europe as a whole, there is no loss. The homogenization of the “losing” country’s flora is exacerbated by the fact that more than half of plant species listed as invading a particular European country are from other European regions. Winter et al. say a similar pattern has been found in North America.

The picture is more complex for small isolated ecosystems. Carvallo and Castro (2017), writing about isolated volcanic islands in the southeastern Pacific Ocean, introduction of large numbers of non-native plant species has not caused extinction of native plant species. It has, however, resulted in the homogenization of the islands’ floras.

These authors worry that this reduction in phylogenetic diversity could have detrimental impacts for ecosystem function and ecosystem services.  (Interestingly, at the level of order or family rather than species or genus, the combined effects of species introductions and extinctions did not change the islands’ taxonomic diversity. They don’t explicitly say whether that fact might mitigate effects on ecosystem function.)  

What is the situation in Hawai`i? The Islands are the “capital” of both extinction and invasion. I know the Hawaiian flora has very high levels of endemism and of endangerment. In addition, naturalized non-native plant taxa constitute up to 54% of the archipelago’s flora (Potter et al. 2023). However, it is probably extremely difficult to distinguish the impacts of introduced plants separate from the impacts of the many non-native animals, e.g., feral hogs. 

Extinction by Introduction

It has been reported that invasive species have caused the extinction of at least seven species of plants on the Cape of Good Hope and endangered another 14% (Houreld 2024). Unfortunately, the report doesn’t specify whether the non-native species are plants or animals. Either way, this is a tragedy. I remind you that the Cape Floral Kingdom is Earth’s smallest Plant Kingdom in geographic size (78,555 km2), and extremely important in uniqueness. According to the article in The Washington Post, two-thirds of the 20,400 plant species growing in South Africa are endemic – found nowhere else on Earth.

Nearly a decade ago, Downey and Richardson objected to measuring the impact of introduced plant species by considering only total extinction of native plant species. They complain that this approach fails to recognize that plants experience a long decline before reaching extinction. They divide this decline into six “thresholds”. Downey and Richardson say there is abundant evidence of invasive plants driving native plants along this extinction trajectory. For example, increases in non-native plant cover or density that result in decreased native plant species diversity or richness equates, under their hierarchy, to the native species crossing from the first to second threshold. They note there are also examples of species causing “extinction debts”. That is, the extinction occurs long after the invader is introduced and initiates a native species’ decline. They call for conservationists to intervene earlier in that trajectory.

The Global Assessment on Biodiversity and Ecosystem Services was recently published by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.  This report notes that there are at least 1,061 invasive plants on Earth. In terrestrial systems, invasive plants are the taxonomic group most frequently reported as having negative impacts, especially in cultivated areas, plus temperate and boreal forests. As I have noted above, non-native plant taxa constitute a particularly high proportion of the flora on islands. The assessment found that the number of non-native plants exceeds the total number of native plants on more than one quarter of the Earth’s islands. However, this report does not distinguish the number of species endangered by plant invasions from the number of species endangered by invasive species of all taxonomic groups.

Tiburon mariposa lily (Calochortus tiburnensis) – a federally Threatened species in California; photo by T.J Gehring via Flickr

None of the experts denies the impact of extinction on biodiversity. Extinction represents the loss of phylogenetically and taxonomically unique organisms. This loss is exacerbated if some taxonomic groups are at disproportionately higher risk of extinction. Introduced non-native species compensate for these losses only to a point (Daru et al.). In Europe, Winter et al. found that extinctions usually befall specialized endemic or rare species, often from species-poor families. On the other hand, successful invaders are often ecological generalists with large ranges, often belonging to species-rich families. This results in the pronounced decrease of phylogenetic and taxonomic ß-diversity within and between regions to which the rare species are unique.  

All these experts agree that species declines — short of extinction — have severe impacts on ecosystem functions, and even evolution.

Yang et al. emphasize that the rapid and accelerating loss of regional biotic uniqueness changes biotic interactions and species assemblages, with probable impairment of key ecosystem functions. Daru et al. stress that biotic homogenization— declining ß-diversity—reduces trait and phylogenetic differences between regions. Conceding that the consequences of this global biotic reorganization on ecosystems are poorly understood, Daru et al. cite increasing evidence that biotic heterogeneity provides insurance for the maintenance of ecosystem functioning in a time of rapid global change. They assert that declining ß-diversity is a more characteristic feature of the Anthropocene than species loss.

Winter et al. also state that the phylogenetic structure of a species assemblage represents the evolutionary history of its members and reflects the diversity of genetic and thus morphologic, physiologic, and behavioral characteristics. High phylogenetic diversity might enable rapid adaptation to changing environmental conditions.

According to Daru et al., the loss of 14 billion years of evolutionary history has affected some regions particularly. The most disturbed biotas include those of California and Florida; Mesoamerica; the Amazon; the Himalaya-Hengduan region; Southeast Asia; and Southwest Australia. These are regions that experienced spectacular taxonomic radiation over time, and now have both high levels of threat and also species invasion.  

Carvallo and Castro, focused on the Pacific islands, call for integrating the two parallel channels of conservation that currently operate separately: those focused on reversing plant extinctions and those focused on reducing invasions. They call for a biogeographical approach that addresses all causes of phylogenetic homogenization.

Tetragonia tetragonoides – the most widespread invasive plant on these Pacific islands; photo by Jake Osborn via Flickr

I believe all these experts, in all their papers, have made the case for such integration world-wide.

Invasive plants’ impact on non-plant species

While I have focused here – and in most of my blogs more broadly — on impacts on wild, native plant communities, it is clear that alterations to floristic communities influence other taxonomic groups. A couple of years ago I summarized findings by Douglas Tallamy and colleagues on what happens to insects – and their predators – when a landscape is dominated by introduced plant species.

In short, domination by non-native plants – whether invasive or just widely planted – suppresses the numbers and diversity of native lepidopteran caterpillars. One study cited in the blog found that 75% of all lepidopteran species were found exclusively on native plant species. Non-native plants in the same genus as native plants often support a similar but depauperate subset of the native lepidopteran community. Tallamy and colleagues conclude that a reduction in the abundance and diversity of insect herbivores will probably cause a concomitant reduction in the insect predators and parasitoids of those herbivores – although few studies have measured this impact beyond spiders, which are generalists. Tallamy focuses on birds.

In the same blog I reviewed publications by Lalk and colleagues, which examined interactions between invasive woody plants and arthropod communities more broadly. They decried the insufficient data about most of these interactions.

A few weeks ago I saw a report of an unexpected impact of invasive plants: roots of beach naupaka [beach cabbage or sea lettuce] (Scaevola sericea) are penetrating sea turtle nests so aggressively that they kill the unhatched turtles. Apparently this is happening at several sites in the Caribbean, where the plant is not native (Houreld 2024). I could find no scientific reports of this phenomenon. One reference noted that a related species (S. taccada) can form large, dense stands that might prevent adult sea turtles’ access to nesting areas (Swensen et al. 2024).

Sources:

Daru, B.H., T.J. Davies, C.G. Willis, E.K. Meineke, A. Ronk, M. Zobel, M. Pärtel,  A. Antonelli,  and C.C. Davis. 2021. Widespread homogenization of plant communities in the Anthropocene. NATURE COMMUNICATIONS (2021) 12:6983. https://doi.org/10.1038/s41467-021-27186-8 

www.nature.com/naturecommunications

Downey, P.O. and D.M. Richardson. 2016. Alien plant invasions and native plant extinctions: a six-threshold framework. AoB Plants, 2016; 8: plw047 DOI: 10.1093/aobpla/plw047; open access, available at http://aobpla.oxfordjournals.org/

Houreld, K. 2024. “Parched Cape Town copes with climate change by cutting down trade.”. The Washington Post. February 29, 2024.

Potter, K.M., C.Giardina, R.F. Hughes, S. Cordell, O. Kuegler, A. Koch, and E. Yuen. 2023. How invaded are Hawaiian forests? Non-native understory tree dominance signals potential canopy replacement.  Landsc Ecol https://doi.org/10.1007/s10980-023-01662-6

Swensen, S.M., A. Morales Gomez, C. Piasecki-Masters, N. Chime, A.R. Wine, N. Cortes Rodriguez, J. Conklin, and P.J. Melcher. 2024. Minimal impacts of invasive Scaevola taccada on Scaevola plumieri via pollinator competition in Puerto Rico. Front. Plant Sci. 2024; 15: 1281797.

Yang, Q., P. Weigelt, T.S. Fristoe, Z. Zhang, H. Kreft, A. Stein, H. Seebens, W. Dawson, F. Essl, C. König, B. Lenzner, J. Pergl, R. Pouteau, P. Pyšek, M. Winter, A.L. Ebel, N. Fuentes, E.L.H. Giehl, J. Kartesz, P. Krestov, T. Kukk, M. Nishino, A. Kupriyanov, J.L. Villaseñor, J.J. Wieringa, A. Zeddam, E. Zykova. and M. van Kleunen. 2021. The global loss of floristic uniqueness. NATURE COMMUNICATIONS (2021) 12:7290.

https://doi.org/10.1038/s41467-021-27603-y

Winter, M., O. Schweiger, S. Klotz, W. Nentwig, P. Andriopoulos, M. Arianoutsou, C. Basnou, P. Delipetrou, V. Didz.iulis, M. Hejdah, P.E. Hulme, P.W. Lambdon, J. Pergl, P. Pys.ek, D.B. Roy, and I. Kuhn. 2009. Plant extinctions and intros lead to phylogenetic and taxonomic homogenization of the European flora  PNAS Vol 106 # 51 December 2009

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

or

www.fadingforests.org

Too Many Deer; Too Few Forest Seedlings & Wildflowers

white flowered trillium (Trillium grandiflorum); via PICRYL One of the “charismatic wildflowers” mentioned by Blossey and colleagues

Bernd Blossey, Darragh Hare, and Don Waller have published a plea that America’s federal government take the lead in formulating a new national program on managing deer. Otherwise, they fear that deer populations will not be reduced to ecologically sustainable levels. I find their argument convincing and well-sourced. I agree that Americans need to figure out how to address this threat. (The full citation is at the end of this blog).

First, Blossey and colleagues describe the damage caused by overabundant deer:

  • severe declines in populations of many native forest herbs and shrubs, probably including disappearing wildflowers;
  • their replacement by non-native species that are less palatable;
  • poor regeneration of many canopy hardwood species;
  • decreased forest resilience, lowering  forests’ ability to adapt to stressors, especially climate change;
  • decreased ability of forests to deliver benefits that are of increasing value to many people;
  • increased prevalence of wildlife and human diseases associated with the spread and size of  growing tick populations; and
  • people – and deer — killed vehicle accidents on roads.

The widespread impacts of white-tailed deer (Odocoileus virginianus) in forests of the East are well-documented (see my previous blogs for a few examples; scroll below the “Archives” to find “Categories”). Blossey and colleagues note examples of similar impacts in the West, attributed to elk (Cervus elaphus) and black-tailed and mule deer (Odocoileus hemionus).

The authors review the decimation of deer populations in earlier centuries and the efforts of state wildlife agencies to rebuild their populations during the 20th Century. The problem, in their view, is that federal and — especially — state wildlife agencies have retained their traditional focus on managing wildlife for recreational hunters. However, recreational hunters make up a small and shrinking proportion of all Americans. Many more people now engage in “non-consumptive” enjoyment of wildlife.

lack of regeneration in Rock Creek Park, Washington D.C.; photo by Sam Sheline, NatureServe, via Flickr

State agencies’ narrow focus might partly arise from fragmented authorities. Agencies other than wildlife departments are responsible for addressing some repercussions of overabundant deer. These include threats to human health, loss of agricultural crops.

For several reasons, Blossey and colleagues call for federal leadership.  They think that only a national strategy can address, in a holistic way, the interrelated deer, human health, forest, and biodiversity crises. The strategy’s goal should be to protect species that are in decline because of over-browsing by deer and to avoid further declines in environmental and human health.

The authors reason that states are tied to traditional constituencies. Also, they have difficulty acting across jurisdictional boundaries. Second, few state wildlife agencies have authority to protect plant and invertebrate species. Yet these are the taxa most directly affected by overabundant deer. Blossey and colleagues point out that, of the ~1,300 species listed under the federal Endangered Species Act, 942 are plants and 287 are invertebrates.

They point out that deer also suffer the effects of overpopulation. Chronic wasting disease is spreading. It causes a slow, agonizing death of affected animals. Another 2.1 million deer are killed each year in vehicle crashes. [According to the World Animal Foundation, the current number of deer killed in traffic crashes is 1.8 million — 300,000 fewer.) Again, these deaths are often gruesome. Finally, the principal population “control” now is death by starvation in winter. This, too, is cruel. 

Blossey and colleagues say that return of large predators, even where feasible, will not result in sufficient reduction in deer populations. Nor will encouragement of greater hunting pressure on does.

They note that the federal government owns nearly 30% of the United States’ terrestrial surface area. Management is divided among many agencies – National Park Service, Fish and Wildlife Service, Bureau of Land Management, USDA Forest Service, Department of Defense, and many smaller agencies.  Management approaches vary. However, it would be possible to bring them into agreement – although, in some cases, this would require new legislation.

Another issue requires resolution:  federal agencies’ authority to manage wildlife on federal land.. The states have repeatedly claimed constitutional and legal authority to manage (vertebrate) wildlife on the federal lands within their borders. This assertion was countered years ago by Nie et al. (2017):

‘Federal land management agencies have an obligation, not just the discretion, to manage and conserve fish and wildlife on federal lands. … [M]ost states have not addressed the conservation obligations inherent in trust management; rather, states wish to use the notion of sovereign ownership as … a source of unilateral power but not of public responsibility. Furthermore, the states’ trust responsibilities for wildlife are subordinate to the federal government’s statutory and trust obligations over federal lands and their integral resources.’

Blossey and colleagues assert that managing wildlife (typically defined as mammals, birds, and fish) is much broader than establishing hunting seasons or methods. Furthermore, the concept of “public trust resources” means resources should be managed for all citizens, not just the fewer than 10% of US residents who hunt. A growing proportion of society expects this management to support healthy and diverse environments.

The authors stress that reducing deer overpopulations is necessary to meet numerous policy goals. These include fulfilling obligations under international treaties related to climate change, invasive species, and threatened species; restoring and conserving the nation’s forests to provide habitat; and adopting “nature-based” climate adaptations, such as carbon sequestration. They express the hope that recent presidential mandates to better quantify and value natural assets will increase awareness of the harm caused by deer overpopulation. Their proposed national strategy would develop goals and metrics to match specific environmental and human health outcomes.

Of course, management of deer must extend beyond federal property lines. This will require cooperation among states, Tribes, and private landowners.

The paper proposes the North American Waterfowl Management Plan as a model. Under this scheme the US Fish and Wildlife Service works with states, tribal governments, Mexico, and Canada to ensure accurate information on waterfowl populations a to calculate harvest levels. States implement their assigned quotas through their own regulations. Waterfowl hunters purchase Duck Stamps to fund the monitoring efforts. This program has worked well for most species covered by the program. Waterfowl are one of the few bird groups that have not declined dramatically.

Reducing deer populations will probably require lethal control. Studies indicate that at least 60% of does must be removed from a population to reduce herd sizes over time. Other means have been attempted at regional or larger landscape levels, such as sterilization, fertility control. These methods have failed even when paired with recreational hunting. Lethal approaches will probably distress many people. However, Blossey, Hare, and Waller believe the program would be supported if it is understood to be undertaken with the goal of improving the health of both humans and also the environment.

In the end, Blossey, Hare, and Waller say they are not willing to leave the killing to cars, disease, and starvation. They emphasize our moral responsibility to protect humans and the many other species that rely on diverse ecosystems. Our policies and choices created the problem, so we must try to correct it.

SOURCES

Blossey. B., D. Hare, and D.M. Waller, 2024. Where have all the flowers gone? A call for federal leadership in deer management in the US. Front. Conserv. Sci. 5:1382132. doi: 10.3389/fcosc.2024.1382132

Nie, M., C. Barns, J. Haber, J. Joly, K. Pitt and S. Zellmer. 2017. Fish and Wildlife Management on Federal Lands: Debunking State Supremacy. Environmental Law, Vol. 47, no. 4 (2017).

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

or

www.fadingforests.org

Forest Regeneration Again … Deer!

photo by Eli Sagor via Flickr

I have recently recent blogged several times about threats to regeneration of eastern forests. Most of the underlying studies stress the role of deer browsing as a major driver of suppression of native plant species and proliferation of non-native ones. Most studies discussed at a recent Northern Hardwood research forum (USDA, FS 2023b Proceedings) found that deer browsing overwhelms other disturbances, such as fire and canopy gaps that typically promote seedling diversity. Miller et al. also stressed the importance of the deer-invasive plant complex in interrupting regeneration in National parks. Reed et al. found that, on the Allegheny Plateau of western Pennsylvania, high deer densities at the time stands formed reduced tree species diversity, density, and basal area – changes that were still detectable decades later.

On the other hand, Hovena et al. found that at their study sites in Ohio, interaction between non-native shrubs and soil wetness overshadowed even the impact of deer herbivory on the species richness and abundance of seedlings.

Unlike the others, Ducey et al. don’t mention deer as a factor in their analysis of regeneration in a forest in the northern half of New Hampshire. They focus on the minimal impact of silvicultural management. Its effect is secondary to overall forest development as the forest ages. Is it possible that overabundant deer are not a factor in the Bartlett Experimental forest.

American elm (Ulmus americana); photo by F.T. Campbell

Some of the studies acknowledge the impacts of non-native insects and pathogens. The most thorough discussion is in Payne and Peet. They note that specialist pathogens have caused the loss of important tree species, specifically elms and dogwoods plus the impending widespread mortality of ash. Such mortality is resulting in drastic and long-lasting shifts in community dynamics.

Ducey et al. anticipate pest-driven reversals of increases over the decades of eastern hemlock (Tsuga canadensis) and American beech (Fagus grandifolia). Also, they expect that white ash (Fraxinus americana), which has a minor presence, will disappear.

Miller et al. also stressed the importance of emerald ash borer-induced suppression of ash regeneration in some National parks . The authors also noted the threat to beech trees from beech leaf disease in other parks. Hovena et al. state that the interaction between non-native shrubs and soil wetness was more influential than ash mortality in shaping woody seedling communities.

Reed et al. considered the role of non-native earthworm biomass on plant species’ growth.

But too many of the studies, in my view, make no mention of the probably significant role of non-native insects and pathogens.

It is perhaps understandable that they don’t address emerging pests that either have not yet or have barely reached their study sites. For example, Hovena et al. and Yacucci et al. [see below] noted growth of one native shrub, Lindera benzoin, in the face of the challenges presented by deer and invading plants. Neither acknowledges the approach of laurel wilt disease, which has not yet become established in Ohio (it has been detected on the Kentucky-Indiana border). Similarly, neither mentions beech leaf disease, although some of the plots studied by Hovena et al. are just east of Cleveland – where BLD was first detected. The location of the Yacucci et al. study is less than 50 miles away. The North Carolina forests studied by Payne and Peet are apparently too far east to be affected by beech bark disease and beech leaf disease is not yet established nearby.

Less understandable is the failure to mention loss of elms – which were abundant in riparian areas until killed off by Dutch elm disease – which was first detected in Cleveland!); or to discuss the impact of dogwood anthracnose. Their focus on the deciduous forest might explain why they don’t mention hemlock woolly adelgid – which is just now invading the area discussed by Reed et al. I suppose the demise of American chestnut was so many decades ago that it is truly irrelevant to current forest dynamics.

A new study raises anew these questions about whether inattention to the role of non-native pests has skewed past studies’ results. Yacucci et al. compared regeneration in a military installation (Camp Garfield), to the results in the surrounding second-growth forest. This choice allowed them to overcome one drawback of other studies: using deer exclosures that are small and of short durations. The military facility covers 88 km2. Inside it, deer populations have been controlled for 67 years at a density of 6.6 – 7.5 deer/km2. Outside, deer have been overabundant for decades. Populations have grown to densities estimated (but not measured) to be at least 30 deer/km2 – more than four times as high.

These authors established 21 experimental gaps in the low-deer-density area and 20 gaps outside the installation where deer densities are high. Some of the gaps in both low- and high-deer-density environs were located on wetter, seasonally flooded soils, some on drier sites. None of the forest sites had experience fire in recent decades.

Their findings support the importance of deer browsing as driver of changes to forest regeneration.

northern spicebush (Lindera benzoin); photo by R.A. Nonemacher via Wikimedia

They found that at low deer densities, gaps develop a vigorous and diverse native sapling layer, including oaks. Total stem density of red and pin oaks was 13 times higher in these gaps than in gaps in high-deer-density locations. Oak saplings were growing into the subcanopy – that is, above deer browse heights. Saplings of other species – i.e., tuliptree (Liriodendron tulipifera), red maple, and ash (Fraxinus spp.) were also flourishing. Also present were dogwood (Cornus florida) and two native shrubs — Lindera benzoin and Rubus allegheniensis. One non-native shrub, buckthorn (Rhamnus frangula), also thrived at low deer densities. Other non-native plant species were far fewer; their cover was 80% lower. Overall, abundance, richness, and diversity of native herbaceous and woody species were 37–65% higher at the low-deer-density study sites. On average tree species were more than twice as tall as in high-deer-density plots.

In high-deer-density plots, non-native species were six times more abundant while native species richness was 39% lower. Diversity was 27% lower. Most native tree species were short in stature and in low abundance. The one exception was black cherry (Prunus serotina), which deer avoid feeding on. The cherry was 95% more abundant in these high-deer-density plots.

There were several surprising results. In most cases, neither years since gap formation nor habitat type (wet vs. dry) had a significant impact on plant diversity, richness, or abundance. The exception was that non-native plant species were more abundant in older gaps where deer densities were high. Yacucci et al. warn that this phenomenon is a potential threat to biodiversity since high deer density is now the norm across eastern forests.

The authors also note that fire has probably never been a factor in these forests, which are primarily beech-maple forests. Certainly there have been no fires over the past 70 years, either inside or outside the military installation.

Yacucci et al. did not discuss past or possible future impacts of non-native insects or pathogens. They did not mention emerald ash borer or dogwood anthracnose – both of which had been present in Ohio for at least two decades when they completed their study. Although they said their study forest was a beech-maple forest, they did not discuss whether beech are present and – if so – the impact of beech bark disease or beech leaf disease. Both of these are spreading in Ohio. The latter was originally detected in 2012 near Cleveland, just 50 miles from the location of Camp Garfield (between Youngstown and Cleveland, Ohio). As noted above, they also did they mention that Lindera benzoin is susceptible to laurel wilt disease.

beech seedlings in Virginia; photo by F.T. Campbell

Proposed solutions to deer over-browsing

Given the combined threat from widespread deer overpopulation and invasions by non-native plants, Yacucci et al. propose enlisting those military posts that regularly cull deer into efforts to conserve and regenerate native plants. Otherwise, they say, the prognosis for regeneration is poor.

Bernd Blossey and colleagues propose a more sweeping solution: implementation of a national policy to reduce deer populations on all land ownerships. They point out that overabundant deer:

  • disrupt the plant communities of affected forests – from spring ephemerals to tree regeneration;
  • promote disease in wildlife and people; and
  • lead to miserable deaths of deer on our highways, through winter starvation, and disease.

They call for federal leadership of coordinated deer-reduction programs. I discuss their proposal in detail in a separate blog.

SOURCES

Ducey, M.J, O.L. Fraser, M. Yamasaki, E.P. Belair, W.B. Leak. 2023. Eight decades of compositional change in a managed northern hardwood landscape. Forest Ecosystems 10 (2023) 100121

Hovena, B.M., K.S. Knight, V.E. Peters, and D.L Gorchov. 2022. Woody seedling community responses to deer herbivory, intro shrubs, and ash mortality depend on canopy competition and site wetness. Forest Ecology and Management. 523 (2022) 120488

Payne, C.J. and R.K. Peet. 2023. Revisiting the model system for forest succession: Eighty years of resampling Piedmont forests reveals need for an improved suite of indicators of successional change. Ecological Indicators 154 (2023) 110679

Miller, K.M., S.J. Perles, J.P. Schmit, E.R. Matthews, and M.R. Marshall. 2023. Overabundant deer and invasive plants drive widespread regeneration debt in eastern United States national parks. Ecological Applications. 2023;33:e2837. https://onlinelibrary.wiley.com/r/eap  Open Access

Reed, S.P., D.R. Bronson, J.A. Forrester, L.M. Prudent, A.M. Yang, A.M. Yantes, P.B. Reich, and L.E. Frelich. 2023. Linked disturbance in the temperate forest: Earthworms, deer, and canopy gaps. Ecology. 2023;104:e4040. https://onlinelibrary.wiley.com/r/ecy

United States Department of Agriculture, Forest Service. 2023a. Proceedings of the First Biennial Northern Hardwood Conference 2021: Bridging Science and Management for the Future. Northern Research Station General Technical Report NRS-P-211 May 2023

Yacucci, A.C., W.P. Carson, J.C. Martineau, C.D. Burns, B.P. Riley, A.A. Royo, T.P. Diggins, I.J. Renne. 2023. Native tree species prosper while exotics falter during gap-phase regeneration, but only where deer densities are near historical levels New Forests https://doi.org/10.1007/s11056-023-10022-w

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

or

www.fadingforests.org

Funding of tree pest programs through §7721

spotted lanternfly – target of many projects funded by USDA’s Plant Pest & Disease Management & Disaster Prevention Program; photo by Holly Raguza of Pennsylvania Department of Agriculture

I am belatedly reporting on the forest-pest projects funded by annual grants under the Plant Pest & Disease Management & Disaster Prevention Program ( of the Plant Protection Act). As usual, APHIS funded projects totaling $62.975 million in FY24. In total, 353 projects were funded. These projects represented 70% of the 504 project proposals submitted (the total funding sought was $106 M).  

APHIS reserved $11 million for responding to P&P emergencies. I applaud this choice since the agency’s annual appropriation provides only a completely inadequate $1 million (or less) to cover emergencies.

APHIS notes that since initiation of the Plant Pest & Disease Management & Disaster Prevention Program in 2009, it has funded more than 5,500 projects with a total of nearly $870 million.

In FY24 the program funded 30 more projects than the 322 projects funded in FY23. blog 320 The FY24 allocation provides more than $1 million more for goal area 1S — Enhance Plant Pest/Disease Survey (from $14.4 million to $15.7 million). This was balanced by small decreases for the other goal areas: enhancing mitigation capabilities received $13.6 million; inspections at domestic sites important in invasive species’ spread received $6.3 million; pest identification and detection received $5.3 million; and outreach and education received $4.1 million.  Projects safeguarding nursery production and those improving pest and disease analysis each received about $2 million.

By my calculation – subject to error! – about $7.5 million went to projects clearly dealing with forest pests [12% of total funding]. This is a welcome increase from FY23 – when funding of such projects reached about $6.5 million (a little over 10%). blog 320 Funding for tree pest projects might be higher. Some $1.9 million is allocated to surveys of grapevines and orchards — hosts of the spotted lanternfly (SLF). However, it is not clear whether these projects are focused on detecting and managing SLF; they might have a much broader goal. If we do include these projects, the total for tree-killing pests rises to $9.4 million — nearly 15% of the total.

Over both FY23 and FY24, the majority of funds went to similar topics: survey and management of sudden oak death in nurseries; surveys for bark beetles, Asian defoliators, and forest pests generally; and outreach programs targetting the spotted lanternfly. In FY24, just under $100,000 paid for efforts to develop tools for rapid detection of laurel wilt link to DMF in avocados – that is, in a crop rather than the natural environment.

No projects addressing tree or forest pests were funded in seven states or territories: Guam, Idaho, Nebraska, New Mexico, Rhode Island, South Dakota, and Utah. This was three fewer states than in FY23. In neither year do I know whether these states submitted proposals in this category that ended up not being funded.

In FY24, spotted lanternfly is by far the pest addressed by the most projects. As noted above, I can’t be precise about the number because of the lack of information about the 23 projects that fund pest surveys of grapes and/or tree crops that are SLF hosts. Eleven projects named SLF specifically. A final project (not included in above) is one funding registration of Verticillium nonalfalfae as a biocontrol for Ailanthus altissima – an invasive tree that is the preferred host of SLF.

The District of Columbia, Kansas, Missouri, and Oklahoma each had one tree pest project funded. In the cases of Kansas and Missouri, the single project was surveys for thousand cankers disease of walnut. Three other states — Iowa, Maryland, and Pennsylvania — also obtained funding to survey for TCD.

The single Oklahoma project concerned efforts to ensure that the sudden oak death pathogen(Phytopthora ramorum) is not present in nurseries. (An Oklahoma wholesaler was one of the hubs of this pathogen’s spread to 18 states in 2019). Eleven other states were also funded to survey their nurseries for P. ramorum: Alabama, Kentucky, Louisiana, Nevada, North Carolina, Ohio, Pennsylvania, South Carolina, Virginia, and West Virginia. P. ramorum is a “program pest” in 2024. That is, APHIS had designated it as a regulated pest for which the agency wished to fill knowledge gaps about its distribution. I note that last year APHIS published a risk assessment that downplayed the likelihood that P. ramorum would establish in the eastern states. Is APHIS seeking more information to test this conclusion?

In a separate case, Oregon received $76,000 to evaluating the threat to nurseries and forests arising from the presence in the state’s forests of two strains or lineages of P. ramorum that previously had not been extant in the environment of North America.

Another approximately 53 projects fund surveys for tree pests other than spotted lanternfly; these are often fairly general surveys, such as for woodborers or “Asian defoliators”. About ten projects fund management efforts – including evaluation of the efficacy of emerald ash borer biocontrol programs.

Last year I noted that two states – Mississippi and Nevada — had projects to survey the “palm commodity”. Hawai`i joined this group in FY24. The project descriptions don’t specify which pests are the targets. The South American palm weevil (Rhynchophorus palmarum) seems most probable; it is established in far southern California and neighboring Mexico. APHIS prepared a risk assessment on the species in 2012. link? In Hawa`ii, concern probably focuses on the coconut rhinoceros beetle (Oryctes rhinoceros). link? There are other threats to palms, e.g., the red palm weevil (Rhynochophorus ferrugineus), link? and a deadly Fusarium wilt. link?

native palms in the desert at Anza-Borrego, California; photo by F.T. Campbell

California has native palms (Washingtonia filifera); southern states from Texas to at least South Carolina have native palmettos. Of course, many species of palms are important ornamental plants in these states, and dates are raised commercially.

Another “program pest” that I have blogged about in the past is box tree moth. link to blog 287 In FY24 five projects addressed this pest, including surveys and efforts to develop better control tools.

beavertail cactus (Opuntia basilaris) in Anza-Borrego, California; photo by F.T. Campbell

I am pleased by continued funding of projects trying to utilize biocontrol agents to protect two groups of cactus severely threatened by non-native insects: lepidoptera that attack flat-padded prickly pear cacti (Opuntia spp.) link to DMF and the mealybug that attacks columnar cacti of Puerto Rico and the Virgin Islands. link to DMF

vulnerable cactus on St. John, US Virgin Islands; photo by F.T. Campbell

I applaud the decision to fund projects focused on determining the efficacy of biocontrol projects. As noted above, three projects are asking these questions in the case of the emerald ash borer. link to DMF  Another project funds production, release, and efficacy evaluation of biocontrol agents targetting Brazilian peppertree in Florida & Texas.

I am also pleased that three projects assist Washington State in its efforts to eradicate the invasion by giant hornets from Asia. link to blogs & Hornet Herald – no detections in 2023 … A company in California also received funding to developing hornet detection tools.

Nineteen projects funded outreach efforts, including continued funding for the “Don’t Move Firewood” program. In addition to those focused on spotted lanternfly, such projects also included other firewood programs, Asian longhorned beetle awareness, and the nursery industry.

I note that while California received funding for 27 projects, none dealt with any of several deadly tree pests extant in the state – goldspotted oak borer, polyphagous and Kuroshio shot hole borers, Mediterranean oak borer, and the palm weevils.  Nor did Hawai`i obtain funding to address rapid ohia death.  Did no one submit proposals to address any of the many issues impeding management of these killers?

South American palm weevil; photo by Allan Hopkins via Flickr

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

or

www.fadingforests.org