July 2022 – Center for Invasive Species Prevention

Breeding Tree Resistance: New Science and Call to Action on New Legislation

grafted beech at Holden Arboretum – for resistance breeding tests

Two USFS experts have published a chapter describing the components needed to succeessfully breed trees resistant to threatening pests. [See full citation at end of blog.]

As Sniezko and Nelson note, the threat from non-native pests and pathogens to forest health and associated economic and ecological benefits is widespread and increasing. Further, once such a pest becomes well-established – as some 400 pest species now are — few strategies to save affected species exist except a program to enhance the species’ pest resistance.

From a technical point of view, Sneizko and Nelson find reason for hope. Most tree species have some genetic variation on which scientists can build. It is likely that a well-designed and well-focused breeding program can identify parent trees with some pest resistance; select the most promising; and breed progeny from those parents with sufficient resistance to restore a species.

Furthermore, they say, progress can be made fairly quickly. Scientists can focus on developing genetically resistant populations while postponing studies aimed at understanding details of the mechanisms and inheritance of the obtained resistance.

Fifty years of breeding have revealed the techniques and strategies that work best. As a result, application of classical tree improvement procedures can lead to development of pest-resistant populations within a decade or so in some cases, several decades in others. The time needed depends on the specifics of the pest-host relationship, level of resistance required – and resources available.

In addition, advances in biotechnology can accelerate development of resistance. Tools include improved clonal propagation, marker-assisted selection, and genetic engineering to add resistance gene(s) not present in the tree species.

Port-Orford cedars in controlled breeding stage at Dorena; photo by Richard Sniezko, USFS

Sniezko and Nelson identify basic facilities needed to support successful breeding programs:

(a) growing space (e.g., greenhouses);

(b) seed handling and cold storage capacity;

(d) field sites for testing;

(e) database capability for collecting, maintaining, and analyzing data;

(f) areas for seed orchard development;

(g) skilled personnel (tree breeders, data managers, technicians, administrative support personnel, and access to expertise in pathology and entomology).

Absolutely essential is continuity of higher-ups’ and public’s support.

Sniezko and Nelson note that a resistance breeding program differs from other research projects in its objectives, magnitude and focus. It is an action-oriented effort that is solution-minded—countering the impact of a major disturbance caused by a pest (in our case, a non-native pest).

See the article for more detailed descriptions of each step in the process.

There are two basic stages:

Phase 1:exploration to assess whether sufficient genetic variation in resistance exists in the species. This involves locating candidate resistant trees, preferably across the affected geographic range impacted by the pest; developing and applying short-term assay(s) to screen hundreds or thousands of candidate trees; and determine the levels of resistance present. In addition to those objectives Phase 1 also begins to evaluate the durability and stability of resistance. It is vital to inform stakeholders of progress and engage them in deciding whether and how to proceed.

Phase 2: develop resistant planting stock for use in restoration. This stage relies on tree improvement practices developed over a century, and applies the knowledge gained in Phase 1. Steps include scaling up the screening protocol; selecting the resistant candidates or progeny to be used; establishing seed orchards or other methods to deliver large numbers of resistant stock for planting; and additional field trials to further validate and delineate resistance.

The authors argue that, at present U.S. forestry programs lack a coordinated, focused resistance breeding program based on the components described above. The Dorena Genetic Resource Center (DGRC) – established in 1966 in Oregon and supported primarily by the USDA Forest Service’s regional State and Private Forestry program and National Forest System — fits the bill. The DGRC has sufficient facilities and resources to screen simultaneously tens of thousands of seedlings from thousands of parent trees belonging to several species. Its staff have built up invaluable experience.

However, the Center is regional in scope and focus. (Staff are pleased to offer advice to colleagues working in other parts of the country.) Who will ensure that we make progress on restoring the dozens of tree species in the East under threat from invasive pests? The ashes, hemlocks, elms, beeches, oaks, Fraser fir, dogwoods, redbay and swamp bays, sassafras all need help (Profiles of these trees’ pest challenges can be found at here. [Chestnut and possibly the chinkapins have the benefit of a well-established charity …]

ash killed by EAB; photo by Nate Siegert, USFS

Three case studies illustrate how the process has worked for three groups of species: 1) five-needle pines (subgenus Strobus); 2) Port-Orford cedar (Chamecyparis lawsonii); 3) resistance to fusiform rust (Cronartium quercuum f. sp. fusiforme – a native pathogen) in southern pines.

New Possibilities

Resistance breeding programs are simplest to undertake when tree improvement facilities and experienced staff are already in place. It is most unfortunate that their number has declined significantly. However, a Congressional mandate to pursue resistance breeding as a strategy can partially retrieve and add needed resources.

Some members of Congress have taken steps to partially restore resistance breeding programs. H.R. 1389, cosponsored by Reps. Welch (D-VT), Kuster and Pappas (both D-NH), Stefanik (R-NY), Fitzpatrick (R-PA), Thompson, (D-CA), Ross (D-NC) Pingree (D-ME). Then-Rep. Antonio Delgado also co-sponsored, before resigning to become Lieutenant Governor of New York.

The bill would establish separate grant programs to fund work under the two phases outlined by Sniezko and Nelson. It relies on grants rather than setting up Dorena-like facilities in other parts of the country. Scientists are already setting up consortia to provide the needed facilities and long-term stability e.g., Great Lakes Basin Forest Health Collaborative. Will that be enough?

The most likely way to create a national tree resistance program is to incorporate these ideas into the next Farm Bill – due to be adopted next year (2023).

You can help by contacting members of the House and Senate Agriculture committees and urging them to include in the bill either H.R. 1389 or a more comprehensive program that does establish centers analogous to Dorena.

Also convey your support to USDA leadership – especially the Forest Service and Agriculture Research Service. (APHIS should be part of the team, but its focus is on strategies with more immediate effect.)

As Sniezko and Nelson state, a key component for success is a core group of stakeholders who

realize the problem (threat to a tree species’ role in the environment);
acknowledge that resistance breeding offers the best avenue for maintaining the species of concern; and
express a willingness to invest in a solution that could take one or more decades.

Will YOU be part of this team?

I note that Bonello et al., 2020 (citation below) suggested a new structure to provide the needed focus and coordination. Adoption of H.R. 1389 would partially realize this. The bill calls for a study to examine the benefits of establishing a more secure foundation within USDA for addressing tree-killing pests.

Scott Schlarbaum made similar points in Chapter 6 of Fading Forests III, published in 2014. See links below.

SOURCES

Bonello, P., F.T. Campbell, D. Cipollini, A.O. Conrad, C. Farinas, K.J.K. Gandhi, F.P. Hain, D. Parry, D.N. Showalter, C. Villari, K.F. Wallin. 2020. Invasive tree Pests Devastate Ecosystems – A Proposed New Response Framework. Frontiers in Forests and Global Change. January 2020. Volume 3. https://www.frontiersin.org/articles/10.3389/ffgc.2020.00002/full

Sniezko, R.A. and C.D. Nelson. 2022. Chapter 10, Resistance breeding against tree pathogens. In Asiegbu and Kovalchuk, editors. Forest Microbiology Volume 2: Forest Tree Health; 1^st Edition. Elsevier

Posted by Faith Campbell

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

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

www.fadingforests.org

Urgent Update on Beech Leaf Disease

banding symptoms of beech leaf disease; photo by Dr. Chagas de Freitas, Ohio State

Experts on beech leaf disease (BLD) hold conference calls every two months. I reported on the May meeting earlier in July. The July conference call of the experts emphasized not only the alarming spread of the disease but also the dilemmas frustrating efforts to slow its spread and protect beech.

Jerry Carlson, chief of forest health protection for the New York Department of Environmental Conservation called beech leaf disease “the next chestnut blight”.

Yet forestry, plant health, and conservation entities have been slow to support research needed to develop protective measures.

As was noted by participants, 10 years after scientists from Lake MetroParks (in Cleveland) first detected disease symptoms, scientists still are unsure about all aspects of BLD and how it spreads. Experts agree that the nematode (Litylenchus crenatae ssp mccannii) must be present to initiate the disease. Other possible factors, especially fungi in the genus Colletotrichum, appear to play important roles in causing the symptoms.

The lack of clarity about the causal agent means that USDA APHIS has not recognized the disease as a priority species for tracking. APHIS has provided some funds. However, scientists seeking to obtain funding through the Plant Pest and Disease Management and Disaster Prevention Program [laid out in the Plant Protection Act’s Section 7721] can’t get traction. Other funding sources also don’t quite fit. For example, the National Science Foundation funds basic, hypothesis-driven, research – not the more applied science needed to address BLD. Some participants wondered whether funding might be sought from wildlife-oriented sources, since beech are so important in providing hard mast, den and nest sites, etc., for a variety of wildlife.

Participants discussed ways to raise awareness – and alarm – in order to build a broader coalition. This effort should include Europe. Although the disease has not yet been detected in Europe, the native beech is vulnerable.

European beech in Rhode Island infected by BLD; photo by Dr. Nathaniel A. Mitkowski, University of Rhode Island

Data indicate that the disease is now significantly more widespread than was known last year. That is, BLD is more widespread from New York to Maine, with New Hampshire reporting its first detection. To the west, BLD has been detected in Michigan and in a forest fragment in western Ohio (near Toledo). Disease severity has also intensified. Of course, the disease is present at least a year before it is detected because leaf symptoms appear in the spring following infection. Therefore its presence is probably wider.

map of BLD presence as of early July 2022 (some states have not yet reported); note the many counties in fuschia – 2022 detections

While mortality of mature beech is still rarely documented, this might be related to difficulties determining the cause of mortality during standard forest health surveys. Participants discussed how to rectify this situation.

Meanwhile, concern is rising – as reflected in Dr. Carlson’s statement.

You can help by asking your state and national officials and conservation organizations to support applied research aimed at clarifying how the disease spreads, what ecological conditions are conducive to disease, improved detection and prediction tools, and possible containment strategies. Let’s overcome the roadblocks impeding protection of this magnificent and ecologically vital tree species.

Is this not worth protecting?

Posted by Faith Campbell

www.fadingforests.org

More & bigger ships, deeper ports = more pests?

Port of Houston – Bayport Container Terminal; photo by Ray Luck via Flickr

The U.S. continued to import large amounts of goods from Asia in the first three months of 2022. During this period, total volume imported from Asia increased to 1.62 million TEU — 31.1% higher than in the same period in pre-pandemic 2019 (Mogelluzzo, B. April 22, 2022).

Due to congestion in West Coast ports, the proportion of Asian goods entering the country through East Coast and Gulf Coast ports also rose in the first quarter of 2022 compared to the same period in 2021: by about 33% along the Atlantic and 6% along the Gulf (Mogelluzzo, B. April 22, 2022). Increases were particularly steep in the south: 9.2% at Savannah; 12.5% at Norfolk; 26% at Charleston; and an astonishing 52.1% through Houston.

Due to Covid-19-related port and factory shutdowns in China, a rising share of imports to the U.S. in 2022 came from other countries in Asia. Imports grew especially from Vietnam but also Thailand, Malaysia, Indonesia, and South Korea (Wallis, K. May 11, 2022).

Port of Long Beach Pier G – ITS – MOL vessel; photo by port authority

Starting in May 2022, West Coast ports began to recover their dominant role – probably because East Coast and Gulf Coast ports were now suffering their own congestion-related delays. Virtually all the restored traffic entered through the Los Angeles-Long Beach port complex; these ports imported a monthly record of 851,956 TEU from Asia in May. Imports through Seattle and Tacoma actually declined from the previous month, while Oakland’s imports from Asia remained steady (Mongelluzzo, June 15, 2022).

Thus, the “baseline” for US imports from Asia each month is now 20 to 30% higher than it was before COVID-19 disrupted supply chains (Mongelluzzo, June 15, 2022).

East Coast Ports Deepening and Expanding to Accept Larger Ships

Meanwhile, East Coast ports continue efforts to deepen their channels and expand their infrastructure so that they can service the larger container ships.

In late June 2022 the US Army Corps of Engineers approved the plan by the Port of New York-New Jersey (PANYNJ) to dredge channels to accommodate more post-Panamax ships. The largest ship that has called at NY-NJ was 16,000 TEU; port officials hope to accommodate ships up to 21,000 TEU, apparently using current capacity (Angell, June 23, 2022; Angell, May 27, 2022). PANYNJ Port Director Bethann Rooney says the port expects to see annual volumes rise to 17 million TEU by 2050, almost double its throughput in 2021 (Angell, May 27, 2022).

The Corps found the PANYNJ plan to be both environmentally and economically sound. The Corps will now seek Congressional funding for the project in the 2024 Water Resources Development Act; the Port Authority will also contribute to the project (Angell, June 23, 2022). We need to be more active in commenting on these port expansion environmental assessments!

The Port of NY-NJ is also seeking to expand storage facilities for incoming shipping containers. Several sites are at various stages of consideration and development; one – part of the “Port Ivory” site on Staten Island – includes a tidal wetland. A November 2021 application by PANYNJ a change-in-use permit is under review by New York State Department of Environmental Conservation (NYSDEC) (Angell, May 27, 2022). Can those interested in environmental protection express their opposition?

The Port of Charleston is expected to finish dredging its inner harbor and channel this year. Last year, the Port of Virginia has received initial funding for a dredging project that should be completed by 2024 (Angell, May 27, 2022).

As we know, numerous tree-killing insects have been introduced from Asia to the ecologically similar forests of eastern North America – often in wood packaging. ALB in Charleston These include Asian longhorned beetle, emerald ash borer, redbay ambrosia beetle, phytophagous and Kuroshia shot hole borers (for profiles of each visit here). Indeed, 15 of 16 non-native bark beetles in the Xyleborini (a tribe of ambrosia beetles) detected in the United States since 2000 are from Asia (Bob Rabaglia, USFS Forest Health Protection, presentation at IUFRO meeting in Prague, September 2021).

Growing numbers of containers entering Atlantic and Gulf Coast ports raises the risk of additional introductions. Insects associated with imports from semi-tropical ports in Vietnam entering the U.S. through Gulf or southern Atlantic ports might well find these regions hospitable. I worry, for example, about the polyphagous and Kuroshio shot hole borers – surely the Gulf Coast provides a more suitable environment for insects from Vietnam and Taiwan than does southern California? And known hosts are present – box elder, willows, sweetgum, mimosa, tree of heaven …

Of course, containers are then sent on from the ports to distribution centers – presenting opportunities for pest introductions in inland areas. New or expanded distribution centers include Atlanta and Appalachian Regional Port and Statesboro Airport in Georgia, Rocky Mount, North Carolina; Huntsville, Alabama; Portsmouth and Front Royal, Virginia (Ashe and Angell July 5, 2022). Front Royal is at the northern end of Shenandoah National Park!

European Trade

Meanwhile, U.S. imports from Europe continued at high levels – although they were not breaking records. In the first half of 2022, the U.S. imported just under 1.77 million TEU from Europe. The largest category of commodity from Northern Europe was foodstuffs — 410,930 TEU. Machinery and mechanical products imports – the type of good often associated with infested wood packaging – numbered 228,521 TEU. Vehicles, aircraft, and vessels imports were 107,526 TEU. “Miscellaneous manufactured articles” that include furniture, bedding, mattresses, and light fittings were 132,979 TEU. I expect – although the source does not so state – that this last category includes decorative stone and tile – again, a category often associated with infested wood packaging.

While fewer damaging pests have been introduced from Europe in recent decades, the risk remains.

Updated Haack Analysis

As has been documented repeatedly (e.g., my blogs, including 248), the current approach to curtailing pest introductions associated with wood packaging is not sufficiently effective. Customs officials continue to detect live quarantine pests in wood packaging as it enters the country. However, the exact level of this threat is unclear since the only assessment was based on data from 2009 (Haack et al., 2014). I eagerly await the results of Bob Haack’s updated analysis, which I hope will be published soon.

SOURCES

Angell, M. NY-NJ port lays groundwork for larger ships ahead of dredging. May 27, 2022. https://www.joc.com/port-news/us-ports/port-new-york-and-new-jersey/ny-nj-port-lays-groundwork-larger-ships-ahead-dredging_20220527.html

Angell, M. NY-NJ deepening study gets US Army Corps blessing. June 23, 2022. https://www.joc.com/port-news/us-ports/port-new-york-and-new-jersey/ny-nj-deepening-study-gets-us-army-corps-blessing_20220623.html?utm_campaign=CL_JOC%20Ports%206%2F29%2F22%20%20%20REDO_PC00000_e-production_E-140850_SA_0629_0900&utm_medium=email&utm_source=Eloqua

Ashe, A. and Angell, M. Rising volumes slowing port flow on East, Gulf coasts. July 5, 2022. https://www.joc.com/port-news/us-ports/rising-volumes-slowing-port-flow-east-gulf-coasts_20220705.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%207%2F6%2F22%20NONSUBSCRIBER_PC015255_e-production_E-141183_KB_0706_0617

Knowler, G. Rising US imports keep pressure on trans-Atlantic. July 18, 2022. https://www.joc.com/port-news/international-ports/rising-us-imports-keep-pressure-trans-atlantic_20220718.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%207%2F19%2F22%20NONSUBSCRIBER_PC015255_e-production_E-141796_KB_0719_0617

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

Mongelluzzo, B. U.S. imports from Asia surge to unexpected record in May. June 15, 2022. https://www.joc.com/port-news/us-ports/us-imports-asia-surge-unexpected-record-may_20220615.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%206%2F16%2F22%20NONSUBSCRIBER_PC015255_e-production_E-140076_KB_0616_0617

Wallis, K. Asia shippers plug trans-Pacific export gap from China COVID-19 disruption. May 11, 2022.

https://www.joc.com/maritime-news/trade-lanes/asia-shippers-plug-trans-pacific-export-gap-china-covid-19-disruption_20220511.html?utm_source=Eloqua&utm_medium=email&utm_campaign=CL_JOC%20Daily%205%2F12%2F22%20NONSUBSCRIBER_PC015255_e-production_E-137446_KB_0512_0617

Posted by Faith Campbell

www.fadingforests.org

Funding APHIS & USFS – speak up!

To forest pest mavens:

The House Appropriations Committee has acted on funding for APHIS & USFS in Fiscal Year (FY) 23 – which begins on October 1. While several programs have been funded at an adequate level, funding for others – e.g., APHIS’ “Tree & Wood Pests) still falls short. Please contact your senators and ask them to urge members of the Senate Appropriations Committee to increase funding for this program. Members of the Senate Agriculture and Interior Appropriations subcommittees (those with jurisdiction) are listed at the end of this blog. My rationale for the “asks” are in my earlier blog.

APHIS funding in $ millions

Program	FY 2021 (millions)	FY 2022 enacted	FY 2023 Pres’ request	Our ask	House bill
Tree & Wood Pests	$60.456	$61.217	$62.854	$70	$62.562
Specialty Crops	$196.553	$209.553	$219.533	$219	$219.698
Pest Detection	$27.733	$28.218	$29.854	$30	$29.825
Methods Development	$20.844	$21.217	$21.854	$23	$31.807

The House bill provides significant funding for many traditional agricultural concerns – livestock health, cotton pests, citrus diseases and pests. Programs we lobbied for received less than the Administration requested with the exceptions of Methods Development and Specialty Crops. I found no explanation for the $10 million increase for methods development.

The Committee Report specifies increases for several pests under Specialty Crops, e.g., citrus and grapes. The report also specifies that $18.3 million should be spent to control spotted lanternfly, which is a pest of both agriculture (especially grapes) and forests. The Committee asks APHIS to keep it informed about progress tackling this pest. (Rep. Andy Harris, ranking Republican on the Agriculture Appropriations subcommittee, has an active SLF infestation in his district.)

The report also instructs APHIS to maintain funding for Asian longhorned beetle at previous levels – within the Tree & Wood Pest account. This means that any savings arising from APHIS’ declaration that parts of the Ohio infestation have eradicated must still be spent on this pest. There are several outbreaks where such funds might be spent, including in New York, Massachusetts, remaining areas in Ohio, and South Carolina.

As in past years, the House Report reiterates members’ expectation that the USDA Secretary will use the authority provided in this bill to transfer funds from the USDA Commodity Credit Corporation to obtain funds to address animal and plant pest emergencies that threaten American agriculture. The Committee has appropriated additional money which is intended to enhance, not replace, use of CCC funds. [The Office of Management and Budget has severely curtailed APHIS access to emergency funds.]

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The House Committee has asked that USFS develop a research program that reflects priorities on, inter alia, invasive species. This falls short of my request for earmarking a specific (small) percentage of research funding for invasive species, but it does show Congressional interest in this problem.

one of the diseases needing USFS research: beech leaf disease (photo by Dr. Chagas de Freitas)

In the part of the budget that funds actual management work, Forest Health Management, apparently the $52 million appropriation reflects only a modest increase of funding for managing invasive species everywhere – on federal lands, i.e. National forests and non-federal lands, i.e., “coop” lands. I appreciate the attention to invasive species, especially emerald ash borer; but worry about allocating most funding to managing the impacts rather than pro-actively addressing introduction and spread to new areas.

USFS funding in $ millions

Program	FY 2021	FY 2022 enacted	FY 2023 Pres’ request	My ask	House bill
R&D		$296.6	$317.8	$317.8	$360.4
[FIA]					$37.7 ($15 M increase)
S&P FHM	$46,232	same?	$59.232	$82	$52.232

Research & Development – The Committee Report noted members’ interest in funding specific laboratories, programs, & projects, including several listed areas. The Committee expects USFS to develop a research program that reflects members’ priorities & other priorities critical to forest health, particularly with respect to climate change adaptation, preventing spread of insects and diseases, and watershed improvement

The report states several times that the USFS should assist in control of the emerald ash borer and other invasive pests, especially in areas where ash tree mortality has been high. Such statements are under State and Private Forestry, under both the Forest Health Management and Urban and Community Forests programs. The Committee earmarks $4 million under UCF for management & reforestation – including tree planting & removals — in communities most severely impacted by EAB and other pests. The efforts should prioritize regional, multi-organization collaborations in urban communities most severely impacted by invasive pests like EAB. The committee asks for a report from USFS on major invasive species and progress of remediation and replanting programs.

===========================

Key Members of the Senate Appropriations Committee

STATE	MEMBER	APHIS APPROP	USFS APPROP
AK	Lisa Murkowski		X
Calif	Diane Feinstein	X	X
FL	Marco Rubio		X
HI	Brian Schatz	X
IN	Mike Braun	X
KS	Jerry Moran	X
KY	Mitch McConnell	X	X
MD	Chris Van Hollen		X
ME	Susan Collins	X
MS	Cindy Hyde-Smith	X	X
MO	Roy Blunt	X	X
MT	Jon Tester	X	X
ND	John Hoeven	X
NM	Martin Heinrich	X	X
OR	Jeff Merkley	X	X
RI	Jack Reed		X
TN	Bill Hagerty		X
VT	Patrick Leahy	X	X
WV	Shelly Moore Capito		X
WI	Tammy Baldwin	X

Posted by Faith Campbell

www.fadingforests.org

Updates on 1) hemlocks 2) shot hole borers/Fusarium & 3) beech leaf disease

symptoms of beech leaf disease; photo by Dr. Chagas de Freitas

Three webinars during April and May provided updates on efforts to address three non-native, tree-killing pests: hemlock woolly adelgid (HWA), link invasive shot hole borers (ISHB), link and beech leaf disease (BLD) link. I attended each and summarize here.

Hemlock conservation in North Carolina – the NC Hemlock Restoration Initiative (HRI) see SaveHemlocksNC.org

The webinar was recorded at Hope for the Hemlocks: HWA Management Approaches on Public and Private Lands in North Carolina. You probably need to be a member of the Natural Areas Association to watch the archived version.

I was pleased to learn about the major effort under way in North Carolina, where eastern and Carolina hemlocks are extremely important components of multiple ecosystems. In 2013, the Commissioner of Agriculture decided to make protecting hemlocks a signature project. He wanted to ensure that three state agencies – the Forest Service, Wildlife Department, and State Parks – worked together to improve the efficacy of treating trees. (Treatments available at the time were expensive and time-consuming.)

HRI treatment at Conestee Falls; HRI photo

Thom Green described the result: North Carolina’s Hemlock Restoration Initiative (HRI). The initiative is administered by the Western North Carolina Communities – a non-governmental organization with strong connections to rural communities and a history of successful collaborative projects that support agriculture and forestry. It engages state agencies, local and county governments, local NGOs, and federal agencies and works on both public and private lands with the goal of ensuring that hemlocks can survive to maturity.

HRI staff work with local partners to identify priority hemlock conservation areas (HCAs). It then sends a “strike team” to guide the partners in treating as many trees as possible. (North Carolina allows non-licensed volunteers to apply pesticides under supervision; also, landowners can treat trees on their own property.) These collaborative projects can treat up to 1,000 trees per day.

The chemicals used are imidacloprid and, where poor tree health justifies emergency treatment, dinotefuran. These are usually applied as a soil drench because it is easier for people to transport the equipment into the woods. Bark spray is used in sensitive areas. They have found that imidacloprid provides five to seven years of protection. A new product, CoreTech, is even easier to transport and works much faster than imidacloprid, however, it costs more.

The HRI believes it is minimizing non-target impacts of the neonictenoid imidacloprid because:

hemlocks are pollinated by wind, not insects
- hemlocks don’t exude resins that attract insects
- pesticide applications are tightly targetted at the base of trunk, with 10-foot setbacks from water
- long intervals between treatments (5 – 7 years) allow soil invertebrates to recover

The program has treated 100,000 trees between 2016 and 2021 on state and private lands. Now they are starting the second round of treatments for trees treated at the beginning of the program.

Treatment priorities are based primarily on the extent to which the trees are able to take up the chemical, evaluated by the percentage of the crown that is alive and the density of foliage. Since imidacloprid can take a year to reach the canopy of a mature tree, it is used only on trees with greater than half the crown rated as healthy. When trees have a lower status, dinotefuran is added (because it can reach the canopy within weeks). Trees with less than 30% live crown are not treated.

The Initiative also supports biocontrol programs. It has assisted releases of Laricobius nigrinis (a beetle in the family Derodontidae) and helps volunteers monitor releases and survival. Dr. Green reports that L. nigrinis has spread almost throughout western North Carolina but that questions remain regarding its impact on tree health. He thinks biocontrol is not yet reliable as stand-alone tool; success will require a suite of predatory insects.

Forest Restoration Alliance potting hemlock seedlings; HRI photo

The HRI measures the success of various treatments (Hurray!). “Impact plots” are established at the start of treatment. Staff or volunteers return every three years to monitor all aspects of the health of a few designated trees – including untreated ones. So far, they have seen encouraging responses in crown density and new growth.

Invasive Shot Hole Borers (ISHB) in California

See www.ishb.org and video recordings of the meeting at:

https://youtu.be/RyqJYyLkshk (Day 1); and https://youtu.be/kWmtcbjTczw (Day 2)

A host of scientists from California spent two full days describing research and management projects funded by specific state legislation – Assembly Bill (AB)-2470 on two invasive shot hole borers.

Adoption of this legislation resulted largely from lobbying by John Kabashima. Additional funding was provided by CalFire (the state’s forestry agency). The agency responsible for managing invasive species – California Department of Food and Agriculture (CDFA) had designated these organisms as not a threat to agriculture. So it did not fund many necessary activities.

The Problem and Where It Is

“Fusarium dieback” is the disease caused by this insect-pathogen complex. The insects involved are two ambrosia beetles in the Euwallacea genus – the polyphagous (E. whitfordiodendrus) and Kuroshio (E. Kuroshio) shot hole borers. link to DMFAccording to Dr. Bea Nabua-Behermann, Urban Forestry and Natural Resources Advisor with University of California Cooperative Extension (UCCE), other fungi are present on both beetle species but its matching Fusarium sp. is the principal associated fungus and is required for the beetle’s reproduction. These are Fusarium euwallaceae and F. kuroshium.

As of spring 2022, the beetle/fungus complex has spread as far north as Santa Barbara /Santa Clarita; and inland to San Bernardino and Riverside (see the map here). They are very widespread in Orange and San Diego counties. At least 65 tree species in southern California are reproductive hosts (globally, it is 77 species; see full list here). The preferred and most succeptible hosts are several species in the Acer, Parkinsonia, Platanus, Quercus, and Salix genera. Box elder (A. negundo) is so susceptible that it is considered a sentinel tree.

Because the beetles spend most of their life inside trees, their life cycle leaves few opportunities to combat them. Females (only) fly but tend to bore galleries on their natal tree. Several speakers on the webinar said management should focus on heavily infested “amplifier trees”. Much spread is human assisted since the beetles can survive in dead wood for months if it is damp enough for the fungus. Possible vectors are green waste, firewood, and even large wood chips or mulch.

Management – from Trapping to Rapid Response to Restoration

Akiv Eskalen of University of California Davis discussed trapping and monitoring techniques to confirm presence of the insect and pathogen. Also, he talked about setting priorities for treating trees based on the presence of reproductive hosts, host value, infestation level, and whether the trees pose a safety hazard. The disease causes too little damage to some hosts to warrant management. He emphasized the importance of preventing spread. This requires close monitoring of infested trees to see whether beetles move to neighbors. Dr. Eskalen described a major and intensive monitoring and treatment program at Disneyland. The 600 acres of parks, hotels, and parking lots have ~16,000 trees belonging to 681 species.

Several speakers described on-going efforts in Orange County. Danny Hirchag (IPM manager for Orange County Parks) described how his agency is managing 60,000 acres of variable woodlands containing 42,000 trees, of which 55% are hosts of ISHB and their associated fungi. Of greatest concern are California sycamore and coast live oak in areas of heavy public use. The highest priority is protecting public safety; next is protecting historic trees (which can’t be replaced); third is minimizing impacts to ecosystem services. Orange County Parks is currently removing fewer than 50 trees each year. Hirchag noted the importance of collaborating in the research trials conducted by the University of California Cooperative Extension.

infested California sycamore; photo by Bea Nabua-Behermann

Maximiliano Regis and Rachel Burnap, of County of Los Angeles Department of Agricultural Commissioner/Weights and Measures, described Los Angeles County’s efforts more broadly. The challenge is clear: LA County has more than 160 parks. In 2021, they placed nearly 2,500 traps, mapped infected trees, carried out on-ground surveys to find amplifier trees, removed both amplifier and hazard trees (using funds provided by CalFire), and educated the public. Their efforts were guided by an early detection-rapid response (ED/RR) Plan (2019) developed by Rosi Dagit (see below). While London plane trees (Platanus x hispanica) and California sycamores (Platanus racemose) were initially most affected, now black locusts (Robinia pseudoacacia) and box elders (Acer negundo) are succumbing. [Note: both are widespread across North America.] The researchers are trying to determine why some areas are largely untouched, despite the presence of the same tree species. Regis and Burnap noted the increasing difficulty getting confirmation of the pathogen’s presence because laboratories are overwhelmed. They continue looking for funding sources.

Rosi Dagit, Senior Conservation Biologist, Resource Conservation District of the Santa Monica Mountains, described the creation of that ED/RR system for Los Angeles County as a whole, without regard for property lines. Participants established random study plots across the entire Santa Monica Mountains Natural Recreation Area (NRA), based on proximity to areas of particularly sensitive ecological concerns. The fact that the NRA’s forests are aging and that the risk of infestations is especially high in riparian forests helped persuade policy-makers to fund the effort. The accompanying rapid response plan informs everyone about what to do, who should do it, and who pays. This information incorporates agencies’ rules about what and where to plant. It also provides measures to evaluate whether the action was effective. It did take more than two years for the county to set staffing needs etc.

John Kabashima link discussed his criteria for replanting and ecosystem restoration following tree removal in the southern California region. He recommends prompt removal of amplifier trees – especially box elder and California sycamore. He relies on replanting guidance developed by UC-Irvine (which is on the website) – especially avoiding monocultures. Kabashima reiterated the importance of close monitoring to track beetle populations and responding quickly if they build up.

Economics of Urban Forests and Cities Most at Risk

Karen Jetter (an economist at the UC Agriculture Issues Center) has developed a model to compare the costs of an early detection program to the environmental and monetary costs of infestation by Fusarium disease. She noted that early detection and monitoring programs are often hard to justify because — when they are successful — nothing changes! She found that averted or delayed costs (including tree removals, lost ecosystem services, lost landscape asset value [replanting value] and the cost to replant) always far exceeded the cost of monitoring programs. Unfortunately, a written report about this effort (Jetter, K., A. Hollander, B.E. Nobua-Behrmann, N. Love, S. Lynch, E. Teach, N. Van Dorne, J. Kabashima, and J. Thorne. 2022. Bioeconomic Modeling of Invasive Species Management in Urban Forests; Final Report) appears to be available only through the University of California “collaborative tools” website dedicated to practitioners and stakeholders engaged on ISHB issues. If you are not a member of the list, contact me using the comment button and ask that I send it to you. Include your email address (the comment process makes determining emails difficult if not impossible.)

Shannon Lynch (UC Davis) developed a model to estimate vulnerability of urban areas based on phylogenetic structure (relationship between tree species), host abundance, and number of beetle generations/year (linked to temperature). She found that areas with less favorable host communities can become vulnerable if the climate becomes favorable. Where the host community is already favorable, climate not important.

She evaluated 170 California cities based on their tree inventories. The cities at highest risk were San Diego, Los Angeles, the San Francisco Bay area, and the Central Valley – e.g., Sacramento. For areas lacking tree inventories, she based her risk determination on the estimated number of generations of beetles per year – based on climate. This analysis posited a very high risk in the eastern half of southern California and the Central Valley. Participants all recognized the need to apply this model to cities in Arizona and Nevada.

Possible Management Strategies

Shannon Lynch (UC Davis) studied whether endophytes might be used to kill the Fusarium fungi. She reported finding 771 fungal strains and 657 bacterial strains in tree microbiomes. Some of the fungal isolates impeded growth of the Fusarium fungi in a petri dish. She began testing whether these fungi can be used to inoculate cuttings that are to be used for restoration. She also planned to test more endophytes, and more native plant species to explore creation of a multi-fungus cocktail.

Richard Stouthamer of UC Riverside is exploring possible biocontrol agents. Of three he has evaluated, the most promising is Phasmastichus sp., which is new to science. He is still trying to establish laboratory cultures so he can test its host specificity.

Beech Leaf Disease (BLD) – Ongoing Research by the BLD Research Group

See bldresearch@lists.osu.edu

At this meeting, scientists described research aimed at improving basic understanding of beech leaf disease’s causal agents, its mechanisms of spread, etc. Their findings are mostly preliminary.

These findings are of greatest importance now:

presence of the nematodes varies considerably across leaf surface – if one collects samples from the wrong site on leaf, one won’t detect nematode (Paulo Vieria, Agriculture Research Service)
- developing predictive risk maps that combines temperature, humidity, elevation, soils (Ersan Selvi, Ohio State). So far, he has found that BLD is greater in humid areas – including under closed forest canopies. The USFS is funding studies aimed at incorporating disease severity in detection apps.
- determining extent of nematode presence. Sharon Reed of Ontario has found nematode DNA in trap fluids throughout the Province. It is much more common at known disease sites. Reed is also studying the presence of arthropods on beech leaves and buds.

Longer term findings and questions

possible vectors:
- nematode DNA has been detected from birds – although it is not clear whether the DNA came from bird feces, feathers, or dust (DK Martin)
- a few live nematodes have been extracted from the excrement of caterpillars that fed on infected leaves (Mihail Kantor, ARS)
- nematode damage to leaves:
  - presence of the nematode in leaf buds before they open (Vieria and Joe Mowery, both ARS). The nematode can create considerable damage in leaf buds before they open. Nematodes are present as early as October of the preceding year.
  - damage to leaves by nematode (Mowery, ARS) Leaf epidermal cells are distorted, stomata blocked, chlorobasts are larger than normal, irregular shape
- possible management tools
  - are there parasites that might attack the nematode? (Paulo Vieria, ARS)
  - experimental treatment of infested trees using phosphite (Kandor, ARS)
- ecology: how do root microbiomes compare on infested and healthy trees? (Caleb Kime, Ohio State; and David Burke, Vice President for Science at Holden Arboretum)

infested European beech in Rhode Island; photo by Dr. Nathanial A. Mitkowski

Posted by Faith Campbell