plants as pest vectors – Page 5 – Center for Invasive Species Prevention

Thirty Years of Tree Pest Analysis, Continued – Risks of New Introductions

It is widely recognized that invasions of non-native species occur as a consequence of international trade (see Seebens et. al. 2017 – full citations at the end of this blog). This is as true for non-native forest pests as for any other bioinvader – see Aukema et al. 2010; Liebhold et al. 2012, Lovett et al. 2016. In fact, gross domestic product – as an indicator of levels of trade — is a better predictor of the number of forest pest invasions in a given country than the country’s amount of forested land (Roy et al. 2014).

shipping containers at port of Long Beach, California

As I noted in my previous blog, I began studying and writing about the threat to North America’s forests from non-native insects and pathogens in the early 1990s. I reported my analyses of the evolving threat in the three “Fading Forests” reports – coauthored by Scott Schlarbaum – in 1994, 2003, and 2014. These reports are available here.

I document here that both introduction and spread of pests within the country have continued apace. While significant efforts have been made to prevent introductions (described briefly under the “Invasives 101” tab of the CISP website), they have fallen short. As I noted in Fading Forests III, programs aimed at preventing spread of pests within the country remain fragmented and often are unsuccessful.

The Challenge: Huge Volumes of goods are moving, providing opportunities for pests

Since 1990, volumes of imported goods more than quintupled. Within the U.S., a total of 17,978 million tons of goods were transported in 2015; 10,776 million tons of this total by truck. About one-third of this total – 5,800 million tons – was moved farther than 250 miles. These vehicles moved on a public roads network of 4,154,727 miles (US DOT FFA). Consequently, once a pest enters the U.S., it can be moved quickly into every corner of the country.

Introductions

By and large, establishment of tree-killing pests has occurred at a fairly steady rate of about 2.5 per year, with “high-impact” insects and pathogens accumulating at 0.43 per year (Aukema et al. 2010). Since introductions did not rise commensurately with rising import volumes, Lovett et al. (2016) concluded that the recently adopted policies for preventing introductions referenced above are having positive effects but are insufficient to reduce the influx of pests in the face of ever-growing global trade volumes. The study’s authors went on to say that absent more effective policies, they expect the continued increase in trade will bring many new establishments of non-native forest pests.

One group of forest pests did not enter at a steady rate, but rather entered at a higher rate since 1985 – wood-boring insects. Experts concluded that the increase probably reflected increases in containerized shipping (Lovett et al. 2016). At the global level, the rate of fungal invasions has also recently been reported to be increasing rapidly (Roy et al. 2014).

Asian longhorned beetle

Geography of trade patterns also matters. Opening of trade with China (in 1979) offered opportunities for pests from a new source country which has a similar climate and biology. Roy et al. describe the importance of phylogenetic relatedness of pests and of tree hosts in explaining tree species’ vulnerability to introduced pests. The most vulnerable forests are those made up of species similar to those growing in the source of the traded goods – i.e., the temperate forests of the northeastern U.S. – when goods are imported from similar forested areas of Europe and Asia. Chinese-origin wood-boring pests began to be detected around 1990. This already short interval probably underestimates how quickly pests began arriving; detection methods were poor in those years, so a pest was often present for close to a decade before detection.

Between 1980 and 2016, at least 30 non-native species of wood- or bark-boring insects in the Scolytinae / Scolytidae were newly detected in the United States (Haack and Rabaglia 2013; Rabaglia et al. 2019). Over the same period, approximately 20 additional tree pests were introduced to the continental states (Wu et al. 2017; Digirolomo et al. 2019; R. Haack, pers. comm.) plus about seven to America’s Pacific islands. Not all of the new species are highly damaging, but enough are. See my previous blog here.

Many of the tree-killing pests were probably associated with pathways other than wood packaging. These include 6 of the 7 Agrilus species, sudden oak death pathogen, three pests of palm trees, the spotted lanternfly, beech leaf disease; and the pests introduced to America’s Pacific Islands.

HIGH-RISK PATHWAYS OF INTRODUCTION

Already in the 1990’s it was evident that better preventing pest introductions would depend on shutting down the variety of pathways by which they move around the world. At that time, attention focused on imports of logs and nursery stock (nursery stock makes up one component of a broader category called by phytosanitary agencies “plants for planting”). Both logs and “plants for planting” had well-established histories of transporting pests and import volumes were expected to grow. We have since learned that there are many more pathways!

Plants for Planting

Imports of “plants for planting” (phytosanitary agencies’ term, which encompasses nursery stock, roots, bulbs, seeds, and other plant parts that can be planted) have long been recognized as a dangerous pathway for introduction of forest pests. For example, this risk was the rationale for adopting the 1912 Plant Quarantine Act. Charles Marlatt, Chairman of USDA’s Federal Horticultural Board (see “Then and Now” in Fading Forests III here), wrote about the risk in National Geographic in April 1911 (urging adoption of the 1912 law) and again in August 1921. See also Brasier (2008), Roy et al. (2014), Liebhold et al. (2012), Jung et al. (2016).

Japanese cherry trees being burned because of scale infestation
January 28, 1910; Agriculture Research Service

Of the 91 most damaging non-native forest pest species in the U.S. (Guo et al. 2019), about 62% are thought to have entered North America with imports of live plants. These include nearly all the sap-feeding insects, almost 90% of the foliage-feeding insects, and approximately half of the pathogens introduced during the period 1860-2006 (Liebhold et al. 2012). Specific examples include chestnut blight, white pine blister rust, Port-Orford-cedar root disease, balsam woolly adelgid, hemlock woolly adelgid, beech scale, butternut canker, dogwood anthracnose, and sudden oak death. In more recent years, introductions via this pathway possibly include ‘ōhi‘a rust, rapid ‘ōhi‘a death pathogens, and beech leaf disease. The gypsy moth, while a foliage feeder, was not introduced via imports of live plants.

The APHIS annual report for 2018 reported that in that year we imported 18,502 shipments containing more than 1.7 billion plant units (plants, bulbs, in vitro materials, etc.).

Liebhold et al. 2012, relying on 2009 data, found that about 12 percent of incoming plant shipments had symptoms of pests – a rate more than 100 times greater than that for wood packaging. Worse, a high percentage of the pests associated with a shipment of plants is not detected by the federal inspectors. The meaning of this finding is unclear because the study did not include any plant genera native to temperate North America and APHIS points out that infestation rates varied considerably among genera in the study. However, APHIS has not conducted its own analysis to document the “slippage rate” on imports of greatest concern to forest conservationists, i.e., imports of woody plants. I provide details on pests detected on imports of woody plants in recent in my blog here.

Clearly the risk of pest introductions continued at least until recently. I reviewed an APHIS database listing pests newly detected in the country during the period 2009-2013. I concluded that approximately 37 of the 90 “new” pests listed in the database (viruses, fungi, aphids and scales, whiteflies, mites) were probably introduced via imports of plants, cuttings, or cut foliage or flowers. I discussed these matters in greater detail here.

Adoption of a new regulatory regime governing imported plants for planting (Q-37 regulation) in 2018 is too recent to for us to see its impact. But the new regulation sets up a process under which APHIS can impose more protective regulations on specific types of plants or plants from certain countries of origin to counter a perceived concerning level of risk. Until APHIS begins activating its new powers by negotiating more protective regulations governing plant imports from high-risk sources, it seems unlikely there will be any meaningful change in the introduction rates.

Crates, Pallets, and Other Forms of wood packaging (solid wood packaging, or SWPM)

Recognition of the risk associated with wood packaging is much more recent. In 1982, a USDA risk assessment concluded that the wood boring insects found in crates and pallets were not of great concern (USDA APHIS and Forest Service, 2000). However, contradictory indications were quickly documented – including from APHIS’ own port interception data – which the agency began collecting in 1985. Over the 16-year period 1985-2000, 72% of the 6,825 bark beetles (Scolytidae) intercepted by APHIS were found on SWPM (Haack 2002). Cerambycids (longhorned beetles) and buprestids (jewel beetles) make up nearly 30% of insects detected in wood packaging over the last 30 years (Haack et al. 2014).

Detection of outbreaks of the Asian longhorned beetle and other woodborers in the mid-1990s made it clear that wood packaging was, indeed, a high-risk pathway.

Of the 91 most damaging non-native pest species in the US, 30% probably arrived with wood packaging material or other wood products (Liebhold et al. 2012). This group includes many of the most damaging pests, the deadly woodborers – Asian longhorned beetle, emerald ash borer, redbay ambrosia beetle, possibly the polyphagous and Kuroshio shot hole borers.

As noted above, introductions of wood borers have risen in recent decades, widely accepted as associated with the rapid increase in containerized shipping after 1980. In 2009 it was estimated that 75% of maritime shipments were packaged in crates or pallets made of wood (Meissner et al. 2009). A good history of the global adoption of containerized shipping is Levinson, M. The Box: How the Shipping Container Made the World Smaller and the World Economy Bigger (Princeton University Press 2008)

The simultaneous opening of trade with China (in 1979) offered opportunities for pests from a new source country which has a similar climate and biology. Chinese-origin wood-boring pests began to be detected around 1990. This already short interval probably underestimates how quickly pests began arriving; detection methods were poor in those years, so a pest was often present for close to a decade before detection.

I have already documented numerous times that, despite the U.S.’ implementation of the International Standard of Phytosanitary Measures (ISPM) #15 in 2006, live quarantine pest woodborers continue to enter the U.S. in wood packaging. The best estimate is that 0.1% of wood packaging entering the United States is infested with wood-borers considered to be quarantine pests (Haack et al. 2014). More than 22 million shipping containers entered the U.S. via maritime trade in 2017 (US DoT). As noted, an estimated 75% of sea-borne containers include wood packaging. Applying the 0.1% estimate to these figures results in an estimate that as many as 17,650 containers per year (or 48 per day) transporting tree-killing insects enter the U.S.

Over a period of nine years – Fiscal Years 2010 through 2018 – U.S. Customs and Border Protection (CBP) detected more than 28,600 shipments with wood packaging that did not comply with ISPM#15 (Harriger presentations to the annual meetings of the Continental Dialogue on Non-Native Forest Insects and Diseases). While most of the non-compliant shipments were wood packaging that lacked the required mark showing treatment per ISPM#15, in 9,500 cases the wood packaging actually harbored a pest in a regulated taxonomic group.

Disturbingly, 97% of the shipments that U.S. CBP found with infested wood packaging bear the ISPM#15 mark certifying that wood had been fumigated or heat-treated (Harriger 2017). CBP inspectors tend to blame this on widespread fraud in use of the mark. On the other hand, one study found that larvae can survive both treatments – although the frequency of survival was not determined. It was documented that twice as many larvae reared from wood treated by methyl bromide fumigation survived to adulthood than larvae reared from heat-treated wood; the reason is unclear (Nadel et al. 2016).

The APHIS’ record of interceptions for the period FYs 2011 – 2016 contained 2,547 records for insect detections on wood packaging. The insects belonged to more than 20 families. Families with the highest numbers of detections were Cerambycids – 25% of total; Curculionidae – 23% (includes Dendroctonus, Ips, Orthotomicus, Scolytinae, Xyleborus, Euwallacea); Scolytidae – 17% (includes true weevils such as elm bark beetles); Buprestids – 11%; and Bostrichidae – 3%. Not all of the insects in these groups pose a threat to North American plant species.

One encouraging data point is that since 2010, there have been no detections of species of bark and ambrosia beetles new to North America in the traps deployed by the USDA Forest Service Early Detection and Rapid Response program (Rabaglia 2019). The 2014 recognition of the Kuroshio shothole borer apparently did not result from this trapping program.

There have been several changes in the wood packaging standard and its implementation by CBP since 2009, the year Haack et al. 2014 analyzed the “pest approach rate”. APHIS has not carried out a study to determine whether these recent changes have reduced the approach rate below Haack’s estimate of 0.01%. Consequently, we do not know whether these changes have reduced the risk of pest introductions.

Other Pathways That Transport Fewer Pests – Some of Which Have High Impacts

Insects that attach egg masses to hard surfaces can be transported by ship superstructures, containers, and hardsided cargoes such as cars, steel beams, and stone. While relatively few species have been moved in this way, some have serious impacts. The principal examples are the gypsy moths from Asia, which feed on 500 species of plants (Gibbon 1992).

The United States and Canada have a joint program – under the auspices of the North American Plant Protection Organization (see RSPM #33) aimed at preventing introduction of species of Asian gypsy moths. The NAPPO standard originally went into force in March 2012. Under its terms, ships leaving ports in those countries during gypsy moth flight season must be inspected and cleaned before starting their voyage.

Gypsy moth populations rise and fall periodically; it is much more likely that egg masses will be attached to ships during years of high moth population densities. These variations are seen in U.S. and Canadian detection reports – as reported here.

While most AGM detections are at West Coast ports, [here; and here] the risk is not limited to that region. AGM have been detected at Wilmington, NC; Baltimore, MD; Charleston, SC; Savanna and Brunswick, GA; Jacksonville, FL; New Orleans, LA; Houston and Corpus Christi, TX; and even McAlester, OK.

Nor is the risk limited to the ships themselves. In 2014, more than 500 Asian gypsy moth egg masses were found on four shipments of imported steel slabs arriving at ports on the Columbia River in Washington.

Between 1991 and 2014, AGM was detected and eradicated on at least 20 occasions in locations across the United States (USDA AGM pest alert). Additional outbreaks have been discovered and eradication efforts undertaken in more recent years.

A second example is the spotted lanternfly (SLF) (Lycorma delicatula), which was first detected in southeast Pennsylvania in autumn 2014. It is native to Asia; it is believed to have entered the country as egg masses on imported stone.

While SLF is clearly a pest of agriculture – especially grapes and tree fruits – its importance as a forest pest is still unclear. Many native forest trees appear to be hosts during the insect’s early stages, including maples, birches, hickories, dogwoods, beech, ash, walnuts, tulip tree, tupelo, sycamore, poplar, oaks, willows, sassafras, basswood, and elms. Adult lanternflies strongly prefer the widespread invasive species tree of heaven (Ailanthus altissima).

As of August 2019, SLF was established in parts of five states: Delaware, Maryland, New Jersey, Pennsylvania, and Virginia. It was detected as having spread to a 14^th county in Pennsylvania; five new counties in New Jersey. APHIS is working with state departments of Agriculture in these states, as well as supporting surveys in New York, North Carolina, and West Virginia (USDA APHIS DA-2019-20, August 7, 2019). Apparently the detections of a few adults – alive or dead – in Connecticut and New York had not evolved into an outbreak. See description and map here.

Imports of logs – roundwood – seem inherently risky. Certainly Dutch elm disease was introduced via this pathway. However, there have been few pest introductions linked to this pathway in recent years, probably because we import most of our unprocessed lumber from Canada. (I provide considerable data on U.S. roundwood imports in Fading Forests III here.)

Decorative items and furniture made of unprocessed wood certainly have the potential to transport significant pests (USDA APHIS 2007). Examples include boxes and baskets; wood carvings; birdhouses; artificial Christmas trees or other plants; trellises; lawn furniture. To date, apparently, no high-impact pest has been introduced via this pathway, although pests intercepted on shipments have included Cerambycids from Asia, e.g., velvet longhorned beetle and here.

Alarmed by high numbers of infested shipments from China, APHIS first suspended imports of such items temporarily; then adopted a regulation (finalized in March 2012 – USDA APHIS 2012).

APHIS has not taken action to prevent introductions on such items imported from other countries – although the North American Plant Protection Action adopted a regional standard making the case for such action and outlining a risk-based approach (NAPPO RSPM#38).

Snails on Shipping Containers

Snails have been detected on shipping containers and wood packaging for decades. In 2015, APHIS stepped up its efforts to address this risk through bilateral negotiations with Italy and launching regional and international efforts to develop guidance for ensuring pest-free status of shipping containers (Wendy Beltz, APHIS, presentation to National Plant Board, 2018 annual meeting).

SPREAD WITHIN THE UNITED STATES

Major pathways for human-assisted spread of pests within the country are sales of plants for planting, movement of unprocessed wood – especially firewood, and hitchhiking on transport vehicles. Since most forest pests are not subject to federal quarantine, any regulatory programs aimed at preventing spread depend on cooperation among the 50 states. None of these pathways is regulated adequately to prevent pests’ spread. See Chapter 5 of Fading Forests III here.

And since neither federal nor state agencies do significant enforcement of existing regulations, preventing spread often depends upon pest awareness of, and voluntary compliance by, individuals and companies.

Even pests subject to a federal quarantine are not prevented from spreading. Plants exposed to the sudden oak death pathogen were shipped to 18 states in spring 2019.

SOD-infected rhododendron plant; Indiana Department of Natural Resources

A collaborative effort by the nursery industry, APHIS, and states (Systems Approach to Nursery Certification, or SANC) is striving to close gaps linked to the standard practice of inspecting plants at the time of shipping, but full implementation of this voluntary program is still years away.

Transport of firewood has been responsible for movement of pests both short distances, e.g., goldspotted oak borer in southern California; and long distances – e.g., emerald ash borer to Colorado. APHIS attempted to develop a certification program but the industry was unable to put one together (see Chapter 5 of Fading Forests III). Current federal and state regulations of firewood are tied to the emerald ash borer quarantine, which APHIS has proposed to terminate. Wood for turning and woodworking has also been linked to movement of pests, e.g., walnut twig beetle/thousand cankers disease from the west to Pennsylvania.

Truck transport of a variety of goods has transported European gypsy moths from the infested areas in the east to the west coast. Transport of stone probably moved spotted lanternfly from southeastern Pennsylvania to Winchester, Virginia.

SOURCES

Aukema, J.E., D.G. McCullough, B. Von Holle, A.M. Liebhold, K. Britton, & S.J. Frankel. 2010. Historical Accumulation of Nonindigenous Forest Pests in the Continental United States. Bioscience. December 2010 / Vol. 60 No. 11

Brasier, C.M. 2008. The biosecurity threat to the UK and global environment from international trade in plants. Plant Pathology (2008) 57, 792-808

Bray, A.M., L.S. Bauer, T.M. Poland, R.A. Haack, A.I. Cognato, J.J. Smith. 2011. Genetic analysis of emerald ash borer (Agrilus planipennis Fairmaire) populations in Asia and North America. Biol. Invasions (2011) 13:2869-2887

Gibbon, A. 1992. “Asian Gypsy Moth Jumps Ship to United States.” Science. Vol. 235. January 31, 1992.

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

Haack R. A. and J.F. Cavey. 1997. Insects Intercepted on Wood Articles at United States Ports-of-Entry and Two Recent Introductions: Anoplophora glabripennis and Tomicus piniperda. In press in International forest insect workshop proceedings, 18 – 21 August 1997, Pucon, Chile. Corporacion National Forestal, Santiago, Chile.

Haack, R.A., F. Herard, J. Sun, J.J. Turgeon. 2010. Managing Invasive Populations of Asian Longhorned Beetle and Citrus Longhorned Beetle:A Worldwide Perspective. Annu. Rev. Entomol. 2010. 55:521-46.

Haack, R.A. and R.J. Rabaglia. 2013. Exotic Bark and Ambrosia Beetles in the USA: Potential and Current Invaders. CAB International 2013. Potential Invasive Pests of Agricultural Crops (ed. J. Peña)

Haack R.A., Britton K.O., Brockerhoff, E.G., Cavey, J.F., Garrett., L.J., 2014. Effectiveness of the International Phytosanitary Standard ISPM No. 15 on Reducing Wood Borer Infestation Rates in Wood Packaging Material Entering the United States. PLoS ONE 9(5): e96611. doi:10.1371/journal.pone.0096611

Haack, R.A., F. H´erard, J. Sun, and J.J. Turgeon. 2010. Managing Invasive Populations of Asian Longhorned Beetle and Citrus Longhorned Beetle: A Worldwide Perspective. Annu. Rev. Entomol. 2010. 55:521–46

Harriger, K. Department of Homeland Security Bureau of Customs and Border Protection, presentation to the Continental Dialogue on Non-Native Forest Insects and Diseases, November 2017.

Jung T, Orlikowski L, Henricot B, et al. 2016. Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora diseases. Forest Pathology 46: 134–163.

Liebhold, A.M., E.G. Brockerhoff, L.J. Garrett, J.L.Parke, and K.O Britton. 2012. Live plant inports: the major pathway for forest insect and pathogen invasions of the US. Frontiers in Ecology.

Lovett, G.M., M. Weiss, A.M. Liebhold, T.P. Holmes, B. Leung, K.F. Lambert, D.A. Orwig, F.T. Campbell, J. Rosenthal, D.G. McCullough, R. Wildova, M.P. Ayers, C.D. Canham, D.R. Foster, S.L. LaDeau, and T. Weldy. 2016. Non-native forest insects and pathogens in the United States: Impacts and policy options. Eological Applications, 26(5) pp. 1437-1455.

Meissner, H., A. Lemay, C. Bertone, K. Schwartzburg, L. Ferguson, and L. Newton. 2009. EVALUATION OF PATHWAYS FOR EXOTIC PLANT PEST MOVEMENT INTO AND WITHIN THE GREATER CARIBBEAN REGION. Caribbean Invasive Species Working Group (CISWG) and Plant Epidemiology and Risk Analysis Laboratory (PERAL) / CPHST. June 4, 2009

Morin, R. presentation at Northeastern Forest Pest Council 81st Annual Meeting, March 12 – 14, 2019, West Chester, Pennsylvania

Nadel, N., S. Myers, J. Molongoski, Y. Wu, S. Linafelter, A. Ray S. Krishnankutty, and A. Taylor. 2016. Identificantion of Port Interceptions in Wood Packaging Material: Cumulative Progress Report, April 2012 – August 2016

North American Plant Protection Organization Regional Standard for Phytosanitary Measures#24 https://www.nappo.org/english/products/regional-standards/regional-phytosanitary-standards-rspms/rspm-24/

North American Plant Protection Organization Regional Standard for Phytosanitary Measures#38 https://www.nappo.org/english/products/regional-standards/regional-phytosanitary-standards-rspms/rspm-38/

Rabaglia, R.J., A.I. Cognato, E. R. Hoebeke, C.W. Johnson, J.R. LaBonte, M.E. Carter, and J.J. Vlach. 2019. Early Detection and Rapid Response. A Ten-Year Summary of the USDA Forest Service Program of Surveillance for Non-Native Bark and Ambrosia Beetles. American Entomologist Volume 65, Number 1

Roy, B.A., H.M. Alexander, J. Davidson, F.T. Campbell, J.J. Burdon, R. Sniezko, and C. Brasier. 2014. Frontiers in Ecology 12(8): 457-465

Seebens et. al. 2017. No saturation in the accumulation of alien species world wide. Nature Communications. January 2017 http://www.nature.com/articles/ncomms14435

U.N. Food and Agriculture Organization International Plant Protection Convention. 2012. International Standards for Phytosanitary Meaures No. 36 Integrated Measures for Plants for planting. Rome. Online at https://www.ippc.int/ Accessed December 7, 2012.

United States Department of Agriculture Animal and Plant Health Inspection Service and Forest Service, 2000. Pest Risk Assessment for Importation of Solid Wood Packing Materials into the United States.

United States Department of Agriculture Animal and Plant Health Inspection Service 2009. Proposed Rule Importation of plants for planting: establishing a category of plants for planting not authorized for importation pending pest risk assessment. Federal Register 74(140): 36403-36414 July 23, 2009.

United States Department of Agriculture Animal and Plant Health Inspection Service 7 CFR Parts 318, 319, 330, 340, 360, and 361. Federal Register Rules and Regulations Vol. 83, No. 53. Monday, March 19, 2018

United States Department of Agriculture, Animal and Plant Health Inspection Service. 2014. Asian gypsy moth pest alert https://www.aphis.usda.gov/publications/plant_health/content/printable_version/fs_phasiangm.pdf and pers. comm.

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United States Department of Agriculture Animal and Plant Health Inspection Service. 2012. Importation of wooden handicrafts from China. Final rule. Federal Register 77(41): 12437-12444. March 1. Online at http://www.gpo.gov/fdsys/pkg/FR-2012-03-01/pdf/2012-4962.pdf. Accessed August 2, 2013.

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https://www.bts.dot.gov/sites/bts.dot.gov/files/docs/FFF_2017.pdf accessed 19/8/13

United States Department of Transportation, Maritime Administration, U.S. Waterborne Foreign Container Trade by U.S. Customs Ports (2000 – 2017) Imports in Twenty-Foot Equivalent Units (TEUs) – Loaded Containers Only

at https://ops.fhwa.dot.gov/freight/freight_analysis/nat_freight_stats/docs/06factsfigures/fig2_9.htm

Williams, L.H. and J.P. La Fage. 1979. Quarantine of Insects Infesting Wood in International Commerce. in J.A. Rudinksy, ed. Forest Insect Survey and Control Fourth Edition 1979

Wu,Y., N.F. Trepanowski, J.J. Molongoski, P.F. Reagel, S.W. Lingafelter, H. Nadel1, S.W. Myers & A.M. Ray. 2017. Identification of wood-boring beetles (Cerambycidae and Buprestidae) intercepted in trade-associated solid wood packaging material using DNA barcoding and morphology Scientific Reports 7:40316

Updates: SOD-infested Plants Shipped Widely; Possible Detections of Beech Leaf Disease in Connecticut and New York

rhododendron infected by P. ramorum;
photo by Indiana Department of Natural Resources

Sudden oak death (SOD) (Phytophthora ramorum)

As I reported in June, Indiana officials had detected the pathogen that attacks more than 100 plant species and that causes sudden oak death in shipments of rhododendron plants from two nurseries in Washington State and British Columbia.

After an unexplained delay, USDA APHIS finally issued an official statement (reported on here) on the situation. Shipments of potentially infected plants already had been sent to 18 states — Alabama, Arkansas, Iowa, Illinois, Indiana, Kansas, Kentucky, Michigan, Missouri, Nebraska, North Carolina, Ohio, Oklahoma, Pennsylvania, Tennessee, Texas, Virginia, and West Virginia. Through “trace forward” inspections, eight of those states have confirmed that their plant retailers received infected plants — Iowa, Illinois, Indiana, Kansas, Missouri, Nebraska, Oklahoma, and Washington.

Plants that test positive for P. ramorum are being destroyed. All plants that have been kept within a two meter radius of an infected plant are also being destroyed. Host plants outside the two meter radius will be sampled intensively.

In addition, several major retailers have agreed to initiate a voluntary recall of plants from their stores.

APHIS advises people in these eighteen states who have bought a rhododendron from a retail outlet to monitor the plant for signs of disease, including leaf spots and shoot dieback. (APHIS provides no reference to a reliable on-line source of information on symptoms.) If people suspect their plant(s) might have the disease, they are advised to contact their local state department of agriculture or a county extension office.

Meanwhile, states are taking steps to inform their citizens. I described the rapid and extensive effort in Indiana in my earlier blog. In Kansas, the Department of Agriculture announced the presence of the pathogen on rhododendron containerized plants on June 7. As in Indiana, most of the plants were being sold by Walmart stores; also one by Home Depot.

In Illinois, state officials announced the pathogen’s presence on July 2^nd. Infected plants were detected at ten Walmarts and at one Hy Vee. Walmart and Rural King are participating in voluntary recalls.

It is unlikely that all the infected plants have been or will be detected and destroyed according to protocols. First, some plants had undoubtedly been sold to people who remain unaware of the issue. Second, other plants were destroyed before they could be inspected by authorities. For example, Virginia authorities told me that the “original suspect plants” at a retail store had been destroyed before they arrived. As a result, authorities cannot know whether infected plants entered the state.

So, is this response adequate? Who will continue outreach to possible purchasers of the plants? Who will enhance monitoring of native vegetation in vulnerable areas, e.g., the Ozarks of Missouri (see the risk maps on pages 86-88 of Fading Forests III, available here.

The Washington State nursery was operating under the program adopted by Federal Order in 2014 and formalized by the regulatory change last year. Because the Washington state nursery had not previously been detected to have infested plants, it was subject only to the standard state phytosanitary inspections with no special attention to possible sources of Phytophthora ramorum inoculum (on plants, in soil or water, in pots that have been used previously, …). Clearly this system was insufficient in this case – as it had been 15 years ago. I do not know what regulations governed the British Columbia nursery or whether plants from BC are inspected more closely by APHIS when they are imported.

I repeat – what lessons will APHIS learn from this disturbing event, and how will it adjust its program? Will the states – 18 of which had to carry out expensive trace-forward programs – demand a more rigorous program?

Beech leaf disease (BLD)

beech leaves with symptoms;
photo by John Pogacnik, Cleveland Metroparks

In January I posted a blog about beech leaf disease. In May and June, two people commented, raising the question of whether BLD was killing trees on their properties in Connecticut. Connecticut’s authorities have visited at least one of these sites, but I have heard nothing about their findings. Photographs from the first site, however, greatly worried Ohio’s experts.

More recently, a person in Westchester County, NY (which borders Connecticut) also raised the alarm. I don’t know whether New York authorities (some of whom have viewed symptomatic trees in western New York and Ohio) have checked this site.

Although these reports have not yet been verified by authorities, I think it would be wise for people throughout the range of American beech – or who have bought European beech trees in recent years from Ohio nurseries – to closely monitor their trees and report any suspicious findings to state authorities.

Posted by Faith Campbell

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Phytophthora ramorum spreads in nursery trade – again!

Rhodendron infected by P. ramorum
photo by Jennifer Parke, Oregon State University

It might be déjà vu all over again.

Fifteen years ago, in the spring of 2004, officials discovered that the disease called “sudden oak death” or “ramorum blight” was present on camellias at a large California nursery that shipped $30 million worth of plants interstate on an annual basis. The nursery was in southern California, far from the wetter areas of northern California where the disease is established in the wild and where regulatory efforts were focused. By the end of 2004, 176 nurseries in 21 states had received infected plants, 125 of which were linked to the California supplier. APHIS and the affected states and nurseries had to spend millions to find and destroy infected plants and conduct intensive surveys to try to ensure this situation was not repeated.

APHIS had begun regulating P. ramorum in nurseries in northern California and Oregon in February 2002. These regulations went through several rounds of change after the 2004 outbreak – discussed in Chapter 5 of Fading Forests III, available here.

Beginning in 2014, APHIS issued two Federal orders that relaxed some of the regulatory requirements for nurseries.

Just this past May, APHIS completed the process of integrating these changes into its formal regulations. (See my blog from May and the text of the new regulations here.) APHIS stated in replying to comments on the rulemaking that it was confident that the new regime provided sufficient protection.

Even as APHIS was finalizing this rule change, Indiana officials discovered that rhododendron plants imported into the state were infected with Phytophthora ramorum!!

Indiana authorities reported that potentially infested plants were received at more than 70 WalMart stores and 18 Rural King stores. By the end of May, state inspectors have destroyed more than 1,500 rhododendrons and have put another 1,500 other plants on hold [source: Indianapolis Star website 29 May, 2019]

Indiana authorities also said that the same source nurseries had shipped plants to nine other states – unnamed.

In mid-June – more than a month after Indiana’s initial detection [Indianapolis Star website 23 May] – APHIS issued a statement. In an email to me, Evelia Sosa, Assistant Director of Pest Management, reported that potentially infested plants from the original suppliers were sent to 18 states! These states are Alabama, Arkansas, Iowa, Illinois, Indiana, Kansas, Kentucky, Michigan, Missouri, Nebraska, North Carolina, Ohio, Oklahoma, Pennsylvania, Tennessee, Texas, Virginia, and West Virginia. State officials Agriculture officials in these States are currently visiting nursery locations to sample plants received from the originating nurseries. Plants that test positive for P. ramorum will be destroyed. All plants that are within a 2 meter radius of an infected plant will also be destroyed. Host plants outside the 2 meter radius will be sampled intensively. Other hosts in the impacted facilities will be monitored for signs of the disease.

Homeowners who might have purchased infected plants are advised by APHIS to monitor them carefully for symptoms; a website is provided — ironically (see below), it is the website of the California Oak Mortality Task Force!

Several of the states which received potentially infected plants have already been through this routine because infected plants were shipped to their nurseries in the 2004 – 2008 period. These include Alabama, North Carolina, and Texas. P. ramorum has been found multiple times in streams or ponds associated with the receiving nurseries (see my blog from May here)

There are several reasons for particular concern. First, the source nurseries were in Washington State and British Columbia. How did the inspection system fail to detect the outbreaks before the plants were shipped? Inspections now include testing of soil and standing water, not just visual inspection of plants. Second, at least some of the infected plants are rhododendrons – which are taxa well known to be vulnerable to the pathogen and the specified focus of detection efforts!

This would seem to verify concerns raised in its comments on the proposal (see the above website) by the California Oak Mortality Task Force, whose members have been studying and managing the outbreak for close to twenty years. COMTF said:

“The revised framework, in many ways, matches the rule structure present in 2004, when the pathogen was inadvertently, potentially shipped to over 1,200 nurseries in 39 states from a few nurseries in Southern California, Oregon and Washington. At that time, the APHIS P. ramorum regulation restricted shipments in the quarantine area, defined as the known infested counties in California and part of Curry Co., Oregon; however, the source nurseries were located in counties where P. ramorum was not present in wildlands. This revised framework does not adequately protect against the reality, that any nursery with host plants, anywhere, is a potential source for infested plants

How is APHIS going to respond – not just in leading efforts to detect and destroy infected plants but also to review its regulatory program? Why did APHIS wait so long to inform me – and presumably others in the public – about this most recent outbreak. (Although as of the time of posting, APHIS had not issued an announcement to the people registered on its stakeholder registry.)

It is not a surprise that APHIS is backing away from regulations. As I document in my blog here, the agency began some years ago to stress collaborative approaches rather than regulations. But there are risks and costs associated with these decisions.

There are troubling situations applying to other forest pests that I hope to blog about soon.

Posted by Faith Campbell

Recent Developments on Sudden Oak Death (Phytophthora ramorum)

tanoak killed by SOD; photo by F.T. Campbell

In recent months there have been several developments affecting efforts to manage the sudden oak death infestation in West Coast states and to prevent its spread to other parts of the country.

1) APHIS regulations

Most notably, APHIS has formalized revisions to its regulations governing nursery stock. This revision was proposed last June (see my blog about this here). The revisions largely implement changes to practices that APHIS had adopted in 4014 and 1015 through Federal Orders. The final regulation is posted here. The new regulation goes into effect on May 20^th.

APHIS received only 10 comments (posted here) on the proposal – from researchers, State agriculture and conservation agencies, environmental advocacy groups, research foundations, and private citizens. I summarized points raised in their comments by CISP and others in an earlier blog.

APHIS responded to most of these comments by reiterating that it has been operating under the current program since 2014 and believes the existing testing protocols and conditions are sufficient to mitigate the risk. The measures to monitor nurseries for infections include testing soil and water, that is, they do not rely exclusively on visual inspection of the plants. This is a step forward. In response to comments by CISP and California Oak Mortality Task Force that all nurseries that grow host plants are a potential source of contamination, APHIS points out that it is not authorized to regulate nurseries that don’t ship plants interstate. This limitation is a serious problem arising from the underlying statute – the Plant Protection Act. APHIS said it would continue to monitor detection of the pathogen, and would reevaluate program protocols “should the need arise” – but it made no promise on how frequently it would reevaluate the program.

APHIS did make some adjustments, based on comments. It agreed to one state’s request that it clarify the minimum number of samples that must be taken during annual inspection of nurseries that had not previously tested positive for the pathogen when those nurseries are located in counties that have SOD infestations in the environment. (Such counties are found only in California and Oregon.)

The agency also said it plans to restructure the list of host species so that it can be updated more quickly. APHIS plans to remove the lists from formal regulations (which require public notice and comment to amend) and post them on the APHIS website. APHIS also expects to merge the lists of proven and associated hosts into a single host list. However, these plans would, themselves, constitute rulemaking and require another public comment period.

APHIS also agreed to reinstate its quarterly program updates, beginning in April of 2019. I have not yet seen an alert telling me how to find the first such update, though.

2) P. ramorum in California and Washington

According to the most recent (April 2019) newsletter of the California Oak Mortality Task Force, tanoak (Notholithocarpus densiflorus) mortality in California attributed to Phytophthora ramorum increased by more than 1.6 million trees across 106,000 acres in 2018. The dead trees are concentrated west of the coastal range.

In the meantime, P. ramorum continues to be detected in nurseries shipping plants from West Coast nurseries. As of April, the California Department of Food and Agriculture had detected P. ramorum in nine nurseries – six from previous years, three new in 2019. (Sixty-four additional infected plants were found in one nursery that had been confirmed positive in an earlier year – raising questions in my mind about the efficacy of the Confirmed Nursery Protocol for eliminating the pathogen.)

As I noted in a previous blog, Washington is finding it difficult to eliminate P. ramorum from the soil of a botanical garden in Kitsap County. For the third time in less than a year, a pond that is downhill from previously “mitigated” sites has tested positive for P. ramorum.

I remind you that scientists do not believe that P. ramorum persists in water – it must be surviving on some plant tissue in both Washington and the Eastern states (see below).

3) P. ramorum in Oregon

The Oregon Department of Forestry (ODF) commissioned a study of the economic impact of Phytophthora ramorum in the state. The study found that to date, sudden oak death has caused minor impacts on the regional economy. There was no impact on timber harvest, export or log prices or recreation or tourism revenues and only anecdotal reports of losses to real estate transaction values in some areas. Meantime, the state and several federal agencies are spending $1.5 million per year to try to contain the outbreak.

However, sudden oak death has the potential to cause harm to core values that elude economic quantification, particularly to tribal cultural values and the “existence value” of tanoak-dominated forests. SOD may be an existential threat to tanoak and associated obligate species (e.g., dusky-footed woodrats, Northern flying squirrels, and Allen’s chipmunks – which are important prey items for northern spotted owl, cougar, coyote, and Pacific fisher. More widespread wildlife — e.g., deer, elk, bear, Coho salmon, and a variety of bird species – might also be harmed.)

Immediate termination of the ODF treatment regime might lead to serious impacts due to more rapid expansion of sudden oak death into Coos County, Oregon. These could include Asian governments restricting timber and fiber exports from southwest Oregon and resulting loss of 1,200 jobs and forest products harvest tax. There might also be a collapse of residential property value and real estate transaction revenues. Finally, there might be a decline in recreation and tourism in affected areas. Maintaining the current treatment regime was expected to delay the spread of SOD north of the Rogue River until 2028, and prevent infestation of Coos County beyond 2038. Continued funding SOD treatments for a total cost of $30 million over the next 20 years could offset loss of 1,200 jobs by 2028 and $580 million in wages from 2028 to 2038.

The study authors note that other factors – such as major wildfires or trade wars – could render these impacts moot.

4) P. ramorum in the East

According to the most recent newsletter of the California Oak Mortality Task Force, over the nine years since 2010, the pathogen has been detected from 11 streams in six eastern states – four in Alabama; one in Florida; two in Georgia; one in Mississippi; one in North Carolina; and two in Texas. P. ramorum has been found multiple times in eight of these streams; it is consistently present in two steams in Alabama, one each in Mississippi and North Carolina.

In 2018, seven states participated in the stream survey (which is operated by the USDA Forest Service): (AL, GA, MS, NC, PA, SC, and TX). This was the smallest number of participating states, which has fallen from14 in 2010 to seven in 2018.

The number of streams surveyed annually has ranged from 45 to 95. The number of streams sampled in 2018 was also close to the smallest number: 47. P. ramorum was detected from six streams – four in Alabama, one each in Mississippi and North Carolina. All positive streams were associated with previously P. ramorum-positive nurseries.

Remember that P. ramorum continues to be detected in West Coast nurseries that ship plants interstate (see the second section of this blog).

Posted by Faith Campbell

Promising Biocontrol to Protect Some Cacti

Photo of infested cactus at Cabo Rojo National Wildlife Refuge, Puerto Rico. Taken August 20, 2018 by Yorelyz Rodríguez-Reyes

Three and a half years ago, I blogged about the threat to columnar cacti in Puerto Rico from the Harrisia cactus mealybug. The mealybug clearly threatens the endemic cacti of the Caribbean islands, and possibly some of the hundreds of other columnar cacti growing across two million square miles of desert ecosystems that straddle the U.S.-Mexico border region.

I am pleased to report that scientists continue efforts to find biocontrol agents to reduce this insect’s damage on Caribbean islands. Much of this work is being done by the Center for Excellence in Quarantine and Invasive Species at University of Puerto Rico. The team consists of Michael West Ortiz, Yorelys Rodrígues Reyes, Ferdinand Correa and Jose Carlos Verle Rodrigues.

As of February 2019, the Center is conducting host specificity tests on a primary parasitoid of the Harrisia Cactus mealybug — Anagyrus cachamai. This wasp was found as a result of almost a decade of searching in South America and other locations. It is native to Argentina and Paraguay (Triapitsyn et al. 2018; sources listed at the end of the blog).The Center also continues surveys and studies of other primary and secondary parasitoids of the mealybug.

The work to develop a biocontrol agent for the mealybug continues despite continuing uncertainty about the true species of the mealybug. At the time of its discovery on Puerto Rico, the mealybug was believed to belong to a species used as a biocontrol agent for invasive cacti in Australia and South Africa, designated as Hypogeococcus pungens. However, H. pungens is now thought to be a species complex, and the species in Puerto Rico differs from the earlier designation (Triapitsyn et al. 2018).

Apparently the mealybug was introduced in Puerto Rico around 2000 — probably on the ornamental common purslane (Portulaca olerácea), an annual succulent. (Note: the introduction was on a host different from the vulnerable cacti.) Within five years of the first detection in San Juan, the mealybug was sighted on cacti on the other side of the island in the Guánica State Forest and Biosphere Reserve. By 2010, the mealybug was widely distributed in most dry districts. Surveys found it in all 11 municipalities surveyed in southern Puerto Rico. At some locations, infestation levels were extremely high – e.g., 86% of stems surveyed were infested at Guánica. Infestation rates were lower in other municipalities. As of 2010, infestations were estimated to be present on about 1,400 km² on the southern coast; the rate of new infestations suggests that the mealybug was spreading rapidly (Segarra-Carmona et al. 2010). I have been unable to obtain more recent estimates.

The mealybug impacts seven of 14 native cactus species occurring in dry forests of the island, including three endemic and two endangered species in the subfamily Cactoideae. The two endangered species are Harrisia portoricensis and Leptocereus grantianus (USDA ARS). The tissue damage caused by the mealybug interferes with sexual reproduction and can cause direct mortality of the plant (Triapitsyn et al. 2018). These cacti provide food or shelter for endemic bats, birds, moths and other pollinators (Segarra & Ramirez; USDA ARS). The mealybug is also now killing native cacti on the U.S. Virgin Islands (H. Diaz-Soltero pers. comm. August 2015).

USDA Funds Conservation Efforts Despite Apparent Absence of a Constituency Calling for Such Action

Efforts to identify and test possible biocontrol agents targetting the Harrisia cactus mealybug received significant funds from the Plant Pest and Disease Management and Disaster Prevention Program. This is a competitive grant program managed by APHIS. It is permanently funded and thus not subject to the vagaries of annual appropriations. Until last year, this program operated under Section 10007 of the 2014 Farm Bill. With passage of a new Farm Bill, it is now designated as Section 7721 of the Plant Protection Act.

Since Fiscal Year 2018, APHIS has had authority to spend more than $60 million per year on this program. In Fiscal Year 2017, , the program provided $120,000 to an unspecified federal agency, $70,000 to an academic institution in Puerto Rico (presumably the Center), $15,000 to another academic institution in California, and $3,000 divided among two APHIS facilities – for a total of $208,000. The next round of funds came in FY19, when the program provided $277,267 to an unspecified federal agency to continue work on biocontrol. In addition, the program provided $78,507 to an unspecified federal agency to “safeguard[e] genetic diversity of native and listed cacti threatened by Harrisia cactus mealybug in Puerto Rico”.

No Apparent Action on Threats to Opuntia Cacti

In my earlier blog, I also described the threat to flat-padded Opuntia (prickly pear) cacti from the cactus moth Cactoblastis cactorum. Various federal, state, and academic entities received $463,000 from the permanent fund in Fiscal Year 2016 and another $100,000 in FY2017. No cactus moth programs have received funds in more recent years.

SOURCES

Segarra-Carmona, A.E., A. Ramirez-Lluch. No date. Hypogeococcus pungens (Hemiptera: Pseudococcidae): A new threat to biodiversity in fragile dry tropical forests.

Segarra-Carmona, A.E., A. Ramírez-Lluch, I. Cabrera-Asencio and A.N. Jiménez-López. 2010. FIRST REPORT OF A NEW INVASIVE MEALYBUG, THE HARRISIA CACTUS MEALYBUG HYPOGEOCOCCUS PUNGENS (HEMIPTERA: PSEUDOCOCCIDAE). J. Agrie. Univ. RR. 94(1-2):183-187 (2010)

Triapitsyn, Aguirre, Logarzo, Hight, Ciomperlik, Rugman-Jones, Rodriguez. 2018. Complex of primary and secondary parasitoids (Hymenoptera: Encyrtidae and Signiphoridae) of Hypogeococcus spp. mealybugs (Hemiptera: Pseudococcidae) in the New World. Florida Entomologist Volume 101, No. 3 411

USDA Agriculture Research Service, Research Project: Biological Control of the Harrisia Cactus Mealybug, Hypogeococcus pungens (Hemiptera:pseudococcidae) in Puerto Rico Project Number: 0211-22000-006-10 Project Type: Reimbursable

West Ortiz, M. pers. comm. February 2019

Posted by Faith Campbell

Beech Leaf Disease Update

A year ago, I alerted you to a new threat to American beech (Fagus grandifolia). In that blog I reported that conservation and park managers in northeastern Ohio had begun noticing troubling decline and mortality of beech saplings beginning in 2012. The problem was spreading: we now know that over the four years between 2012 and 2016, the apparent disease spread from an estimated 84 ha to 2,525 ha within Lake County, Ohio (Ewing et al. 2018; full citation provided at end of the blog).

By 2018, trees with symptoms had been detected in 24 counties across three states and one province: 10 counties in Ohio, 8 counties in Pennsylvania, 1 county in New York, and 5 counties in Ontario). A map is provided in Ewing et al.

The rate of decline within beech stands varies, suggesting that trees differ in susceptibility. This is a promising for breeding resistance (Ewing et al.).

Symptoms

A number of organizations have produced fact sheets and related material. I recommend the fact sheet available here.

Disease Progression

In Northeast Ohio, Cleveland Metroparks’ intensive monitoring program revealed a 4% mortality rate from 2015 to 2017. More than half of the plots now have dead trees that had previously been only symptomatic. Most of the dead trees are small – less than 4.9 cm dbh. However, some larger trees have died and others bore only a few leaves this past summer. Leaves with light, medium, or heavy symptoms of infection – as well as asymptomatic leaves – can occur on the same branch of an individual tree.

The disease seems to spread faster between the stems of trees growing in beech clone clusters by spreading along the interlocking roots.

Serious science effort finally initiated – and funded!

The cause of beech dieback and mortality has still not been definitively determined. Most scientists agree that the cause is some kind of disease agent, not abiotic factors. A growing number of scientists from USDA’s Agriculture Research Service and Forest Service; Ohio’s Division of Forestry and Department of Agriculture; the Holden Arboretum; Ohio State University; and groups in Canada are researching possibilities.

The most promising candidate is a previously undescribed nematode detected by David McCann of the Ohio Department of Agriculture. That nematode has since been described by Japanese researchers on Japanese beech F. crenata (Kanzaki et al.) and given the name Litylenchus crenatae. Thousands of live Litylenchus nematodes (at least 10,000) can swim out from a single leaf. Scientists at the USDA Agriculture Research Service and Holden Arboretum are waiting for bud break this spring to see whether plant material inoculated with the nematode develops disease symptoms.

Still, other possible disease agents could also play a role.

An international working group has been formed to continue studies of both disease agents and disease progression in seedlings, saplings, and mature trees.

Still, no regulation to counter long-range spread via nurseries!

Long range spread of the disease is probably assisted by anthropogenic transport, especially of nursery stock. As I reported in May, an Ontario retailer received – and rejected – a shipment of diseased beech from an Ohio nursery.

Despite the evident risk, no official agency has adopted regulations to prevent spread on nursery stock. None of the states or provinces in which the disease is present has adopted regulations. None of the neighboring states or provinces has acted to protect its nursery industry or forests. Neither USDA APHIS nor the Canadian Food Inspection Agency (CFIA) has adopted regulations. The disease was not mentioned during the annual meeting of the National Plant Board – which took place in Cleveland in August! Connie Hausman of Cleveland MetroParks did include the issue during her presentation on the extensive park complex to the group during the group’s field trip.

The absence of regulation is a puzzling omission because Lake County, Ohio, has many nurseries that grow and ship European beech — which can also be infected by beech leaf disease.

The Importance of American Beech – and Protecting

Our American beech is not a major timber species – in fact, the species is actively disliked by managers focused on timber production because beech bark disease kills trees before they reach commercial size. Beech trees also often have cavities which reduce their timber value – but which are valuable to wildlife.

However, American beech is extremely important ecologically in northern parts of the United States and in Canada east of the Great Plains. Beech is co-dominant (with sugar maple) in the Northern Hardwood Forest. A summary of the species’ ecological importance can be found in Lovett et al. 2006. Beech nuts are a primary source of food for many woodland birds and mammals. In the central part of the northern hardwood forest – including in southern Canada – beech trees are the only source of hard mast. Furthermore, beech trees create a dense canopy; drastic defoliation modifies light levels at ground level, thereby affecting understory competition and other forest ecosystem services. Beech leaf litter decays more slowly than maple’s, which affects nutrient cycling. While beech leaf disease is unlikely to eradicate American beech, it could cause functional eradication of the species. Ohio alone has more than 17 million American beech trees, according to Tom Macy of the Ohio Department of Natural Resources (Ewing et al. 2018).

The threat appears to be widespread because both European (F. sylvatica) and Asian (F. orientalis) beech have shown symptoms. Ewing et al. 2018 call for detection efforts across Northern Hemisphere.

Of course, the species is already under threat from beech bark disease. Promising efforts to breed beech trees resistant to BBD now face the complication of having to incorporate resistance to this new disease (Ewing et al. 2018).

European Beech Weevil

I will remind you that last year I noted a third threat to beech trees – the European leaf weevil. Originally detected in Nova Scotia, it continues to spread. About 95% of beech trees in forest plots near Halifax are dead. In the city, half the beech trees have died and the rest are in severe decline. While neither the province nor CFIA has imposed a quarantine or other regulations to govern the movement of beech material, Canadian officials are exploring possible chemical treatments. They are working with European colleagues to explore biocontrol agents (Jon Sweeney, Natural Resources Canada, pers. comm.).

Conclusion

These new threats are getting far too little attention! Some can be blamed on the difficulty of regulating an unknown disease agent (e.g., beech leaf disease). Attempting this would stretch traditional policy practice and, possibly, legal authorities. And it has not yet been demonstrated that this disease can kill mature beech. However, neither of these caveats applies to the weevil, which is an identified species, documented to kill mature trees, and a problem still not addressed.

Sources

Ewing, C.J., C.E. Hausman, J. Pogacnik, J. Slot, P. Bonello. 2018. Beech leaf disease: An emerging forest epidemic. Short Communication. Forest Pathology 2018;e12488

Kanzaki, N., Y. Ichihara, T. Aikawa, T. Ekino, and H. Masuya. 2019. Litylenchus crenatae n. sp. (Tylenchomorpha: Anguinidae), a leaf gall nematode parasitising Fagus crenata Blume. Nematology. Volume 21: Issue 1

Lovett et al. 2006. Forest Ecosystem Responses to Exotic Pests and Pathogens in Eastern North America. BioScience Vol. 56 No. 5.

Sharon Reed’s presentation on YouTube https://www.youtube.com/watch?v=tDBbik7cUrI

Posted by Faith Campbell

2018 – More Bad News on Sudden Oak Death

Tanoak mortality at Big Sur photo by Matteo Garbelotto

Outbreaks intensified in western North America and Western Europe (UK, France).
Outbreaks are increasingly genetically diverse – raising the possibility of sexual reproduction and evolution.
Evidence accumulated that eradicating Phytophthora ramorum from the environment once it is present is extremely difficult, if not impossible.

Meanwhile, APHIS proposed revisions that would weaken its regulation of nursery stock. See my earlier blog. Copies of all comments can be viewed here.

1) Intensifying Outbreaks

North America

According to the California Oak Mortality Task Force’s (COMTF) November 2018 newsletter, about 50 million trees have been killed by P. ramorum in California and Oregon. This breaks down to:

29 – 44 million tanoaks (Notholithocarpus densiflorus) (1.6 – 2.5% of the species’ total population in California and Oregon);
1.9 – 3.3 million coast live oaks (Quercus agrifolia) and Shreve oaks (Q. parvula var. shrevei), combined (0.4 – 0.7% of their populations); and
up to 1.1 million California black oaks (Q. kelloggii) (less than 0.17% of their population).

Of course, the oaks face additional threats from goldspotted oak borer and polyphagous and Kuroshio shot hole borers hin more southern parts of California.

California bay laurel (Umbellularia californica) is not killed by P. ramorum but instead drives the spread of the outbreak in California. The state has an estimated 91.4 million infected California bay laurel trees.

These estimates are considered to be conservative. They are based only on trees that have been confirmed to be infected by direct, cultural isolation during the period up to 2014 — more than four years ago! And before a sharp intensification of infection (see below).

Data from a USDA Forest Service aerial detection survey – reported in COMTF’s September 2018 newsletter — detected a large increase in tanoak mortality in counties California counties reaching from Mendocino south to Monterey. This intensification in tree mortality was expected because the pattern is already well established: two seasons after a wet winter seasons, trees die. Such a wet and extended winter occurred in 2016-2017.

United Kingdom

Outbreaks of the EU1 strain of P. ramorum on larch (Larix kaempferi) in Scotland have also intensified. The infection is now found throughout much of Scotland, not just in the heavily infested zone in the the southwest part of the country. See updated map of outbreaks on Larch sites in woodland settings at https://scotland.forestry.gov.uk/supporting/forest-industries/tree-health/phytophthora- ramorum?highlight=WyJyYW1vcnVtIiwiJ3JhbW9ydW0iLCIncmFtb3J1bSciXQ

–

There is more on the status of P. ramorum in the the UK (England, Wales, Scotland and Northern Ireland) in a situation report posted by Forestry Commission England in 2018. Find it here: https://www.forestry.gov.uk/pdf/PRamorumSituationReport30June2018.pdf/$FILE/PRamorumSituationReport30June2018.pdfh

As in North America, the large number of outbreaks is attributed to favorable, wet conditions in the summer and fall of 2017. (This situation was summarized in COMTF’s September 2018 newsletter.

France

The outbreak on larch in France, first reported in 2015, is also spreading. This is particularly significant because, first, it is the first report of P. ramorum outside of nurseries and ornamental settings in mainland Europe and, second, because it is a new genotype not tied to any other outbreak. By May 2018, about 80% of the trees in the Saint-Cadou larch plantations in Brittany (Northwest France) were symptomatic or dead in the more infected plots. A second outbreak has been detected a few kilometers away in a mixed forest stand of larch, oak, and sweet chestnut (Castanea sativa). There, disease prevalence was much lower. Both stands have been removed.

(This was also summarized in COMTF’s September newsletter.

2) Increasing Genetic Diversity

EU1 Strain in Oregon

As I have reported in the past, Oregon now has a second strain of Phytophthora ramorum – the “EU1” strain. This opens the possibility of sexual reproduction between it and the NA1 strain already established in forests in Oregon’s Curry County.

According to a presentation by Chris Benemann of the Oregon Department of Agriculture to the Continental Dialogue on Non-Native Forest Insects and Diseases, in 2018 – three years after the initial detection of one tree in 2015 – the number of trees infected by the EU1 strain has risen to 73. Oregon has prioritized removing these trees and treating (burning) the immediate area – now more than 355 acres. The legislature has provided $2.3 million for SOD treatments for 2017-2019. ODA believes that eradication of the EU1 outbreak is still possible.

3) But Is Eradication Possible?

According to the COMTF September newsletter, P. ramorum was detected by a water bait in a small pond downstream from a previously-infected botanical garden in Kitsap County, Washington. The garden undertook extensive mitigation efforts – including soil steaming – and the pathogen had not been detected in this managed landscape for about 2 ½ years. Hundreds of samples of host plants were collected in September, with only one warranting further analysis to determine whether it was positive. Surveys will continue in 2019.

In the East, USDA has baited streams to detect P. ramorum for several years. Seven states participated in the 2018 Spring National P. ramorum Early Detection Survey of Forests: Alabama, Georgia, Mississippi, North Carolina, Pennsylvania, South Carolina, and Texas. As reported in the COMTF’s September newsletter, h292 samples were collected from 48 sites. As in past years, positive samples were collected from streams associated with previously positive nurseries. These included three samples from two locations in Alabama; two samples from one location in Mississippi; and one sample from North Carolina. The Alabama and Mississippi sites have tested positive for approximately a decade.

So, the pathogen is persisting in water – but how? I have been told that P. ramorum requires plant material on which to survive – so how is it persisting without detectable infested plants? Also, does the presence of zoospores pose a threat of infesting streamside plant material? What studies are examining this issue?

Awareness through Art

Artists have transformed a SOD-infected tanoak tree into 7,000 pencils as part of their thoughtful “7,000 Marks” project. They explore issues around global industrial trade, quarantine boundaries as a conservation tools, and the opposing concern that restricting trade can echo a rising tide of xenophobia. You can learn more (and buy pencils) here.

SOURCES

Cobb, R.; Ross, N.; Hayden, K.J.; Eyre, C.A.; Dodd, R.S.; Frankel, S.; Garbelotto, M. and Rizzo, D.M. 2018. Promise and pitfalls of endemic resistance for cultural resources threatened by Phytophthora ramorum . Phytopathology. Early view.

https://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-04-18-0142-R

Harris, A.R.; Mullett, M.S.; Webber, J.F. 2018. Changes in the population structure and sporulation behaviour of Phytophthora ramorum associated with the epidemic on Larix (larch) in Britain. Biological Invasions. 20(9): 2313–2328.

Posted by Faith Campbell

Alarming Picture of Phytophthora Threats to Forests World-wide

Prompted by the rising number of Phytophthora-caused diseases in forests on several continents, in 1999 the International Union of Forest Research Organizations (IUFRO) formed the IUFRO Working Party 7.02.09 ‘Phytophthora Diseases of Forest Trees’. Last spring This group published a global overview of Phytophthora diseases of trees (Jung et al. 2018; see full citation at the end of this blog).

The study covers 13 different outbreaks of Phytophthora-caused disease in forests and natural ecosystems of Europe, Australia and the Americas.

The picture is alarming!

Jung et al. state definitively that the international movement of infested nursery stock and planting of reforestation stock from infested nurseries have been the main pathway of introduction and establishment of Phytophthora species in these forests.

The Picture: A Growing List of Diseases, Species, and Places Affected,

Jung et al. note that, during the past six decades, the number of previously unknown Phytophthora declines and diebacks of natural and semi-natural forests and woodlands has increased exponentially. The vast majority of these disease complexes have been driven by introduced invasive Phytophthora species. In 1996, 50 Phytophthora species were known. In the 20 years since then, more than 100 new Phytophthora species have been described or informally designated. One study (Tsao 1990) estimated that more than 66 % of all fine root diseases and more than 90 % of all collar rots of woody plants are caused by Phytophthora spp. Many of these had previously been attributed to abiotic factors or secondary pathogens. One example – surprising to me, at least – is that decline of mature beech trees in Central Europe is linked to Phytophthora rather than beech bark disease!

Several of the disease complexes described in Jung et al. 2018 are causing heartrending destruction of unique floras, e.g., jarrah, tuart, and other communities of western Australia and kauri forests of New Zealand. The authors expect increasing damage to the Mediterranean maquis in the future. They list these among other examples:

Ink disease of chestnuts worldwide
Oak declines and diebacks in Europe and North America
Decline and mortality of alders (Alnus species) in Europe
Decline and mortality of Port-Orford cedar (Chamaecyparis lawsoniana) in Europe and North America
Kauri dieback in New Zealand link to earlier blog
Decline and mortality of Austrocedrus chilensis and Juniperus communis in Argentina and Europe
Diebacks of natural ecosystems in Australia
Decline and dieback of the Mediterranean maquis vegetation
Decline and dieback of European beech in Europe and the US
Dieback and mortality of southern beech (Nothofagus species) in the United Kingdom and Chile
‘Sudden Oak Death’ and ‘Sudden Larch Death’ in the US and United Kingdom
Leaf and twig blight of holly (Ilex aquifolium) in Europe and North America
Needle cast and defoliation of Pinus radiata in Chile

Several of the Phytophthoras are causing severe damage on several continents:

P. cinnamomi in Europe, North America, and Australia
P. austrocedri in South America, Europe, and western Asia
P. ramorum in Europe and North America
P. lateralis in North America and Europe.

Often, the genetic makeup of the Phytophtoras species varies in these different locations. These differences indicate separate introductions and the existence of sexual reproduction and continuing evolution in response to conditions.

Why Phytophthoras are Spreading via the Plant Trade and Nursery Practices

First, Phytophthora species are able to survive unsuitable environmental conditions over several years as dormant resting structures in the soil or in infected plant tissues. When environmental conditions become suitable, the resting spores germinate – often prolifically. Since visible symptoms might not appear for considerable time after infection because the mechanism is progressive destruction of the fine root system, detection of the disease is delayed, further undermining control.

Second, most of the Phytophthora species causing disease complexes were unnoticed as co-evolved species in their native environment. Often they were unknown to science before their introduction to other continents – where they become invasive on naïve plant species. Consequently, these species are not captured by the international plant health system, which is based on lists of recognized “pest” species.

Third, the common nursery practice of applying fungicides or fungistatic chemicals masks the presence of pathogens – another way plants pass unnoticed through phytosanitary controls. These chemicals do not, however, kill the pathogen.

Fourth, the importation into receiving nurseries of plants from around the world provides ample opportunity for the introduced Phytophthoras to hybridize. The interspecific hybrids may differ in host range and virulence from the parent species, thus making predictions about the potential effects of an ongoing invasion even more difficult.

Fifth, the nurseries or plantings in gardens or restoration projects also provide suitable environments for prolific germination and spread.

All of these risks were first enumerated by the eminent British pathologist Clive Brasier a decade ago! (See Brasier et al. 2008 citation at the end of the blog.)

As Jung et al. 2018 point out, the scientific community has repeatedly urged regulators to require the use of preventative system approaches for producing Phytophthora-free nursery stock (see references in the article). Scientists have provided research-based guidance to reduce the risk of infestation. Such measures are being implemented by only some nurseries in the US. For example, USDA APHIS has specific requirements for nurseries that ship hosts of P. ramorum in interstate commerce after the nurseries or the plants have tested positive. More broadly, APHIS, the states, and the nursery industry are in the second round of pilot testing of an integrated measures approach to managing all pests under the Systems Approach to Nursery Certification (SANC) program

At the international level, the International Plant Protection Convention has adopted ISPM#36, which also envisions greater reliance on systems approaches. However, the preponderance of international efforts to protect plant health continue to rely on visual inspections that look for species on a list of those known to be harmful. Yet we know that most damaging Phytophthoras were unknown before their introduction to naïve ecosystems.

Furthermore, use of fungicides and fungistatic chemicals is still allowed before shipment.

As pointed out by several experts beginning with Dr. Brasier but including Liebhold et al. 2012, Santini et al. 2013, Jung et al. 2016, Eschen et al. 2017, this approach has failed to halt spread of highly damaging pathogens. (I note that the list of such pathogens is not limited to Phytophthoras; see the description of ohia rust in Hawai`i, Australia, and New Zealand).

Jung et al. 2018 also call for increasing the genetic resistance of susceptible tree species. The authors regard this as the most promising sustainable management approach for stabilizing declining natural ecosystems and for reintroducing susceptible tree species at sites with high disease impact. See my blogs about efforts to enhance U.S. tree-breeding posted earlier this year.

SOURCES

Brasier CM. 2008. The biosecurity threat to the UK and global environment from international trade in plants. Plant Pathology 57: 792–808.

Jung, T., A. Pérez-Sierra, A. Durán, M. Horta Jung, Y. Balci, B. Scanu. 2018. Canker and decline diseases caused by soil- and airborne Phytophthora species in forests and woodlands. Persoonia 40, 2018: 182–220 Open Access!

Liebhold AM, Brockerhoff EG, Garrett LJ, et al. 2012. Live plant imports: the major pathway for forest insect and pathogen invasions of the US. Frontiers in Ecology and Environment 10: 135–143.

Santini A, Ghelardini L, De Pace C, et al. 2013. Biogeographic patterns and determinants of invasion by alien forest pathogens in Europe. New Phytologist 197: 238–250.

Tsao PH. 1990. Why many Phytophthora root rots and crown rots of tree and horticultural crops remain undetected. Bulletin OEPP/EPPO Bulletin 20: 11–17

Posted by Faith Campbell

The Latest on Phytophthoras

Phytopthora ramorum on tanoak in California; F.T. Campbell

Nine eastern states are participating in the 2016 USDA National Phytophthora ramorum Early Detection Survey of Forests. Those states are AL, FL, GA, MS, NC, PA, SC, TN, and TX. As of late August, streams in four locations were P. ramorum-positive. Three are in AL, one in MS. All had tested positive in previous years. Also, all have been associated with previously positive nurseries. (Reported in the California Oak Mortality Task Force newsletter for September.) It is reassuring that no new positive locations have been detected. However, on what substrate is the pathogen persisting? Scientists agree that the pathogen does not survive in water (although it is reliably detected by testing in water) but must survive on some plant material – perhaps roots.

P. ramorum also persists in nurseries. Seven California nurseries are participating in the APHIS federal P. ramorum program under which they are allowed to ship host plants interstate. Positive plants have been detected in two of them. One of these nurseries is undergoing the Confirmed Nursery Protocol clean-up. The other has completed the cleanup and has been allowed to resume shipping plants interstate. In both cases, the infected plants were not from the five “high-risk” genera which are the focus of monitoring for the regulatory system — Camellia, Kalmia, Pieris, Rhododendron, and Viburnum. (Reported in the California Oak Mortality Task Force newsletter for September.) I expressed concern about this too-narrow focus in a blog posted in July 2015 – http://nivemnic.us/2015/07/.

I have written about the widespread presence of various Phytophthoras in nurseries in blogs in April (for Europe http://nivemnic.us/2016/04/ ) and July (for California http://nivemnic.us/2016/07/ ). New publications add to this picture.

Junker and colleagues (see references below) report the detection of 15 Phytophthora species in two commercial woody ornamental nurseries (presumably in Europe, since the authors are Europeans). Twelve of the species are previously described but the DNA of three isolates did not match any of the known species. Detections were highest in puddles on nursery pathways; followed by plant residues;, wind-carried leaves; and water and sediment from runoff. The plant samples showed very low infection rates – a disturbing finding given the reliance until recently on inspection of plants to detect the pathogen. (Reported in the California Oak Mortality Task Force newsletter for September.)

New Phytophthora confirmed in U.S.

The United States has the first official confirmed detection of the pathogen Phytophthora quercina. It was found associated with oak trees planted on restoration sites in central coastal California. Although the California detection is the first officially confirmed detection of the pathogen in the U.S., a P. quercina ‘like’ organism has been reported to be associated with oak decline in forests in the Midwest. P. quercina is a pathogen associated with oak decline across Europe. It was rated as the species of highest concern in a USDA Plant Epidemiology and Risk Analysis Laboratory (PERAL) report. Another pathogen, P. tentaculata, was rated fifth on the same list. It was recently found in association with multiple native plant species in California’s native plant nurseries (see my July blog, linked above). See also California Oak Mortality Task Force newsletter at http://www.suddenoakdeath.org/news-and-events/current-newsletter/

Rapid Response Might Have Contained SOD – When will authorities learn this lesson?

Earlier this year, experts on modeling the epidemiology of plant disease concluded that the sudden oak death epidemic in California could have been slowed considerably if aggressive management actions – backed by “a very high level of investment” – had started in 2002. By then, there was sufficient knowledge about the disease to guide actions. Management actions should have focused on the leading edge of the epidemic (admittedly, that edge has proven difficult to detect). The study is by American and British scientists (Cunniffe, Cobb, Meentemeyer, Rizzo, and Gilligan). See reference and news report below.

The authors’ estimate documents the high costs of inaction. This is an important lesson – which has been repeated many times. If only officials from California and APHIS would take this to heart regarding several other forest pests. These include the polyphagous and Kuroshio shot hole borers and even the goldspotted oak borer (all described here).

References

https://www.sciencedaily.com/releases/2016/05/160502161111.htm?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+sciencedaily%2Fplants_animals%2Finvasive_species+%28Invasive+Species+News+–+ScienceDaily%29

Cunniffe, N.J., R.C. Cobb, R.K. Meentemeyer, D.M. Rizzo, and C.A. Gilligan. Modeling when, where, and how to manage a forest epidemic, motivated by SOD in Calif. PNAS, May 2016 DOI: 10.1073/pnas.1602153113

Junker, C., Goff, P., Wagner, S., and Werres, S. 2016. Occurrence of Phytophthora in commercial nursery production. Plant Health Progress. 17:64-75.

Posted by Faith Campbell

Europe moves to curtail forest pest introductions – but strongest measures are hampered by trade rules

ALB in Europe; photo by Doris Holling WSL

Maartje J. Klapwijk and several colleagues have recently taken a hard look at non-native forest pests in Europe. They conclude that current European legislation is inadequate to prevent forest/tree pest introduction, establishment and spread in the European Union. (A link to the article is provided at the end of this post.)

Some of the proactive steps that they recommend, however, will be difficult to enact. International trade rules (World Trade Organization, Agreement on the Application of Sanitary and Phytosanitary Measures – SPS Agreement) require that countries prove that the target commodity in trade presents a significant pest risk – proof that is difficult to obtain before damage has actually occurred.

(I have written extensively about this “Catch 22” – see Fading Forests II here)

Furthermore, European Union rules prevent countries from taking proactive measures to restrict potentially pest-infested plants or wood products being traded from one EU member country to another. However, member countries’ vary in their levels of concern about tree-killing pests. As a result, phytosanitary measures are quite weak in some countries. Once a pest-infested shipment enters a country with a weak phytosanitary system it can be moved freely to any other member country.

Thus, international and EU rules together create a significant risk that a pest will enter, establish, and then be spread by commerce to the rest of the Union.

The authors note that growing trade in living plants and wood products has brought a rise in non-native tree pests becoming established in Europe. The number of alien invertebrate species has increased two-fold since 1950; the number of fungal species has increased four-fold since 1900. Few studies have attempted to quantify the economic impacts of non-native tree-killing pests in Europe. But the authors say that the introduced pests will cause economic damage either directly by reducing the revenue of the country or imposing control costs; or indirectly through trade restrictions or reduced values of real estate.

Among the recent introductions are the pinewood nematode from North America; Asian and Citrus longhorned beetles and ash dieback fungus from Asia; and sudden oak death and other Phytophthora species. (I described the extent of Phytophtphora infestations in European nurseries in a blog posted on April 25.) As a partial response, EU countries have created a network of nurseries intended to serve as an early warning system against further introductions of alien tree pests. (Descriptions of these pests and where they are found are available on the website of the European and Mediterranean Plant Pest Organization (EPPO) here)

ALB introduction sites in Europe

The European Union regulates invasive species through the Environment Directorate-General (DG Environment). However, tree-killing pests and other plant health concerns are the responsibility of a different governmental body, the Directorate-General Health and Food Safety (DG SANCO).

Maartje J. Klapwijk and colleagues note the risk associated with:

crates, pallets, and other forms of wood packaging;
wood chips (Europe imports more than 4 million tons of wood pellets as fuel in order to meet its carbon emission reduction goals) ; and
especially – living plants.

They note that the international community has adopted two international related sanitary agreements : ISPM#15 (wood packaging) and ISPM#36 (living plants). The European Union requires certificates stating that imported plants are free from harmful organisms and that phytosanitary measures stipulated by the importing country have been applied. However, limited resources mean that only a small proportion of living plants, plant material, soil and wood products arriving in Europe can be inspected. “The main purpose of the inspections is to verify whether shipments comply with regulations, rather than to stop potentially harmful organisms …” (my emphasis). Reflecting the differences in levels of concern among EU member states noted above, there are large differences in inspection intensity among the EU member states.

The pertinent European legislation is Directive 2000/29/EC. It relies on a ‘‘black-list’’ of plants and plant products that are banned from import and specifies procedures to apply when any of these banned products is found in the EU. According to Klapwijk and colleagues, these quarantine lists provide insufficient protection because harmful organisms that enter the EU often are unknown prior to establishment.

Aware of the current system’s inadequacies, the EC has proposed a new regulation which would simplify and harmonize plant passports, allow for stricter measures against pests, and address emerging risks from certain living plant imports from some non-EU countries. Instead of listing harmful plant pests, the proposed regulation “sets out the conceptual nature of quarantine pests” and empowers the Commission to adopt measures to control certain pests.

Klapwijk and colleagues praise these actions as a significant step forward. However, they note that the new rules still don’t provide for precautionary assessments of high-risk commodities. Nor do they restrict import of the highest-risk commodities, such as imports of large plants or plants in soil. (my emphasis)

The authors note that other countries take a more pro-active, precautionary stance. Australia and New Zealand require that all imported plant products be assessed and proved safe before import. The U.S. restricts the size of imported plants and does not allow imported plants to be in soil. (The U.S. has proposed a new approach that relies increasingly on integrated measures or systems approaches rather than port-of-entry inspection. However, this proposal has been pending for more than three years. (APHIS explains its proposal here)

The question is, do trade rules allow Europe to apply the same restrictions as other countries? As Klapwijk and colleagues note, the EU cannot adopt more rigorous phytosanitary measures without providing scientific evidence for this necessity. Preparing a risk assessment to make this case will involve considerable work. As part of this process, Europe should announce that it wishes to raise its “level of protection” and that more stringent phytosanitary measures are needed to achieve that new goal.

Meanwhile, the EU can enhance its active detection efforts and “rapid response” capabilities. The new EC directive will require countries in which a new pest is detected to eradicate or contain the pest. However, the response continues to depend on investments and actions by individual Member States – which have often been insufficient.

Klapwijk and colleagues endorse the suggestion by Hulme et al. (2009) that the European Commission establish a single agency to respond to introductions of any kind of invasive species (not just tree pests) – modeled on the European Centre for Disease Prevention and Control.

Finally, Klapwijk and colleagues note the importance of engaging the public. Citizens’ participation can enhance early detection and strengthen public support for management strategies.

CONCLUSIONS

We Americans are very lucky that the U.S. Department of Agriculture had fairly stringent rules governing plant imports before the World Trade Organization and SPS Agreement were negotiated in the 1990s. We don’t have the burden of proving that imports of large plants (small trees!) in soil is too risky. (This not to say that U.S. regulations should not be tightened further for the most high-risk imports. See Fading Forests III here). Europeans should be able to build their case for more restrictive trade rules on existing risk assessments and practices utilized by the U.S., Australia, New Zealand, and others; on the numerous studies published in recent years that describe recent introductions to Europe and the pathways by which they entered; and by the number of those introductions alone. (To see what has been introduced, visit the website of the European and Mediterranean Plant Pest Organization (EPPO) here)

One important step in improving U.S. rules would be to finalize the proposal – put forward in 2013 – to depend more on integrated measures or systems approaches rather than inspection at the port of entry. Join with me in urging the Secretary of Agriculture to finalize this proposal before he leaves office in January. Contact me via the “contact us” button on the webpage to learn how you can help.

The United Kingdom has voted to leave the European Union. This means that the U.K. has the opportunity – and burden – of developing its own phytosanitary regulations. The U.K. has some of the leading forest pathologists and entomologists. The risk is obvious to all – especially Phytophthora ramorum in larch plantations and ash dieback disease in many areas of the country. I hope that the British will seize this opportunity to adopt really effective phytosanitary regulations that can serve as a model for the rest of Europe – and possibly even the U.S.

Sources

Maartje J. Klapwijk, Anna J. M. Hopkins, Louise Eriksson, Maria Pettersson, Martin Schroeder,A°ke Lindelo¨w, Jonas Ro¨nnberg, E. Carina H. Keskitalo, Marc Kenis. 2016. Reducing the risk of invasive forest pests and pathogens: Combining legislation, targeted management and public awareness. Ambio 2016, 45(Suppl. 2):S223–S234 DOI 10.1007/s13280-015-0748-3

Hulme, P.E. 2009. Trade, transport and trouble: Managing invasive species pathways in an era of globalization. Journal of Applied Ecology 46:10-18

Posted by Faith Campbell