July 2020 – Center for Invasive Species Prevention

Another Set of Official Data Demonstrates Impact of Non-Native Forest Pests

Ash forest in Michigan killed by emerald ash borer
photo by Nate Siegert

As I reported in December, the USDA Forest Service Forest Health Management program has been issuing reports on the status of pest invasions, based on annual national Insect and Disease Surveys (IDS). This survey is carried out by low-level aerial surveys of statistically valid geographic units. (For a discussion of quadrat establishment, see the Introduction to the 2019 report here.

Here I compare the pest situation as it appeared in two recent years, based on these surveys: 2017 and 2018.

Of course, two years is too short a time to see trends. The second report provides USFS scientists attempt to provide context by analyzing 20 years of data (Chapter 6 of the 2019 report).

These reports are important sources of data on the status of non-native pests in our forests, but I raise several caveats that necessitate our continuing to rely on additional sources, some of which I have cited in previous blogs. I will address these in greater detail below. But in brief, these caveats are:

1) Major pests – both in extent and damage caused – are not adequately included (see below).

2) The survey technique resulted in delays in detecting mortality. It cannot be used as an early detection tool.

3) There is little analysis of the statistics cited.

Why Stakeholders Cannot Rely on These Two Survey Reports Alone

I hope stakeholders, analysts, and decision-makers will utilize the full range of reports and other data to evaluate the presence and impacts of various invasive pests and pathogens. Even the reports’ authors advise decision-makers to use other forest health indicators in addition to this report. It is not the “fault” of the authors that these reports cannot serve all needs. However, we all need to be aware this caveat.

1. Important Pests Not Adequately Included.

Many of the most damaging non-native pests caused extensive damage before these surveys were initiated. These include white pine blister rust, chestnut blight, Dutch elm disease, butternut canker, Port-Orford cedar root disease, European gypsy moth, and balsam woolly adelgid on Fraser fir. [For further discussion, see pest write-ups here and my earlier blogs reviewing 30 years of engagement and survey data from Shenandoah National Park.]

2. Major Damaging Pests Are Poorly Captured by the Survey Method. Morin found that non-native pests had caused a five percent increase in mortality nation-wide – as measured by tree volume. Three of the species suffering the highest rates of this “exacerbated mortality” are redbay, ash, and hemlock. The current studies’ authors concede all three are poorly detected by the survey methods. The aerial survey techniques are ill-suited to detect mortality of tree species that grow scattered throughout a diverse forest. Other seriously damaging pests that are poorly detected by aerial surveys are Dutch elm disease, white pine blister rust, and thousand cankers disease. Again, see the species write-ups here to be reminded about how great the pest’s impact are. Also review my earlier blog reviewing 30 years of my engagement with the issue and survey data from Shenandoah National Park.

dead redbay in woods
photo by F.T. Campbell

Given these caveats above, what do these studies show us?

Areas surveyed.

Since 1999, the annual Insect and Disease Survey (IDS) has covered on average 266,655,000 ha, although the area varied from a maximum of 320,712,000 ha (in 2007) to a minimum of 202,170,000 ha (in 2017), then increased to 211,34,000 ha in 2018. For reasons not clear to me, the proportion of forested area in the lower 48 states surveyed actually declined from 2017 to 2018 – from 55.1% to 46.6%. In Alaska, the 2017 surveys covered about 7.3% of the total forested area but 12.7% of the forested area in 2018. In Hawai`i, the survey covered about 80.1% of the forested area in 2017, but only 69.4% of the State’s total tree canopy area in 2018.

Tree-Killing Insects and Pathogens Found.

The 2017 survey identified 63 mortality-causing agents and complexes that cumulatively affected 3.27 million ha in the lower 48 states – about 1.3% of the total 252 million ha of forested land in these states. Of these agents of tree mortality, 23 were detected killing trees on areas totaling larger than 5,000 ha each.

The 2018 survey identified seven fewer mortality-causing agents – only 56. These agents were detected on about 2.13 million ha across the lower 48 (slightly less than the combined land area of New Jersey and Rhode Island), or about 0.8% of the total forested area. Of the total, 22 agents were detected killing trees on areas totaling larger than 5,000 ha each.

The more recent report does not discuss these declines from the 2017 findings or whether they might be related to the smaller percentages of forested areas covered by the aerial survey in 2018.

In both 2017 and 2018, as well as in the 20-year trend analysis (Chapter 6 of the report published in 2020), overall mortality is greatest in the West due to the impact of several native western bark beetles. Overall mortality rates in other regions was considered low, despite severe impacts of some non-native species.

The 2017 survey found that the emerald ash borer (EAB) was the most widespread single agent, causing measurable tree mortality on 1.42 million ha. In 2018, the area of EAB damage was reduced by 76% — to just 338,000 ha. (Still, the latter figure represented 15.8% of the total area displaying mortality). These figures were probably underestimates – especially in areas outside North Central Region – because EAB is one of the pests poorly detected by the aerial survey technique – at least when ash are growing scattered in a diverse forest ecosystem. Although the USFS report doesn’t say so, this decline probably reflected the collapse of dead ash trees and reduction in numbers of still-alive but vulnerable ash trees as the EAB invasion wave matured.

The reports document a huge increase in mortality attributed to the sudden oak death pathogen between 2017 and 2018. (SOD is the only widespread non-native agent of mortality on the West coast.) The area affected increased nearly seven-fold – from 6,335 ha in the 2017 survey to 42,771 ha in the 2018 survey. This equated to causing mortality on 3.9% of the total Regional mortality area. This finding parallels finding reported by the California Oak Mortality Task Force. Note that SOD-related mortality was not detected by the aerial surveys until 2008 – 13 year or more after scientists working on the ground detected the presence of the then-unknown pathogen in the forests of California.

tanoak killed by Phytophthora ramorum on Big Sur peninsula
photo by Matteo Garbelotto

Another alarming increase detected in 2018 was that of balsam woolly adelgid (BWA) in the Interior West. BWA-caused mortality was evident on 44,000 ha – 8.4% of the total area with mortality. BWA impacts were especially severe in central Idaho. There are several native pests in the same area. (See BWA write-up here.) BWA was first detected in Idaho in 1983 – 35 years earlier.

Geographic Hot Spots

The EAB caused the principal hot spots in the East. In the USFS North Central Region, 91% of the area suffering tree mortality in 2017 was attributed to the EAB. The EAB was also causing mortality across 10,346 ha (16% of the total areas suffering mortality) in the Northeast (especially Connecticut) and more than 5,000 ha in the South (especially Kentucky). (See my December blog for a discussion of the puzzling situation in several Great Plains ecoregions, where mortality was attributed largely to drought rather than either EAB or Dutch elm disease.)

Another mortality agent in the Northeastern Region was the European gypsy moth. In 2018, it was responsible for tree death on 31% of the total 70,000 ha affected area.

Another hot spot was in Hawai`i. In 2017, about 37,000 ha of mortality was detected. By 2018, the dead zone had increased to 46,000 ha – despite a 12% decrease in the area surveyed. In both years, the data collectors officially called the cause unknown. The reports’ authors stated that the probable cause was they rapid ‘ōhi‘a death fungi. (I ask why the surveyors did not state the cause since rapid ‘ōhi‘a death was identified on the Big Island in 2014.)

Other non-native pests that affected more than 5,000 ha in the lower 48 states in 2017 were the BWA outbreak in the Northeast (20,758 ha, primarily in Maine); beech bark disease (12,222 ha, primarily in the North Central Region), and oak wilt (9,573 ha, primarily in the North Central Region and Texas).

In the Southern Region, mortality agents were detected on 1% or less of the forested area in 2017. In 2018, EAB-caused mortality was detected on 9.7% of the total 13,000 ha area experiencing mortality. An earlier gypsy moth outbreak had apparently calmed. I remind you that the report authors have conceded that laurel wilt and hemlock woolly adelgid are poorly detected by the survey technique.

eastern hemlock in Shenandoah National Park (Virgina)

DEFOLIATORS

The 2017 survey detected defoliation caused by 50 agents and complexes across the lower 48. These impacted 2.3 million ha. The 2018 survey identified six more defoliation agents and complexes (56), but they affected a much smaller area – about 1.72 million ha.

Unsurprisingly, the most widespread was the European gypsy moth. The data demonstrated the gypsy moth’s boom/bust cycle. In 2017, gypsy moth impacts were detected on 39% of the total forested area of the lower 48 states (913,000 ha) in 2017. By 2018, the total area affected by the gyspy moth had fallen to 156,000 ha.

In both years, gypsy moth defoliation was particularly severe in the Northeast Region. In 2018, a second non-native species, browntail moth (Euproctis chrysorrhoea) was also causing severe defoliation in the region, primarily in Maine.

In the South, the European gypsy moth affected only 5.8% of the total area of defoliation; native defoliators predominated.

The report does not discuss the relationship between gypsy-moth caused defoliation and mortality. True, there must be repeated defoliations to cause tree mortality.

Other non-native defoliation agents affecting more than 5,000 ha in the lower 48 in 2017 were the larch casebearer (25,891 ha in the North Central Region and another 7,400 ha in the West Coast Region); and winter moth (12,760 ha in the Northeast Region). Is the decline of winter moth in 2018 data related to introduction of a biocontrol agent?

In 2018, the Larch casebearer (Coleophora laricella) continued to be a significant defoliator, affected 3.1% of the North Central Region’s total defoliated area. A new agent, the balsam woolly adelgid (BWA), was detected defoliating firs in the West Coast Region. The affected area was 15,000 ha – 5% of the total affected area Again, there was no discussion of as to whether defoliation precedes mortality. Admittedly, the progression of BWA damage in firs is extremely complicated.

Alaskan forests suffered widespread defoliation, mostly by native species. The survey detected an unknown canker on quaking aspen (Populus tremuloides).

Twenty Years of Data: Trends

In addition to reporting on the 2018 survey, the more recent report contains an analysis (in Chapter 6) of data over 20 years. The analysis is intended to be used in analyses required under the Resource Protection Act (RPA). The RPA analysis uses the same set of Insect and Disease Survey data, although it groups them in four rather than five regions.

The authors grouped the annual data into four five-year windows (1996-2001; 2002-2006; 2007–2011; 2012-2016).

An overview comprising all mortality agents across the nation found a major “spurt” in area exposed to mortality-causing agents in 2002-2006. The 14.2 million ha was 4.5 times greater than the 3.1 million ha affected in the preceding 1997-2001 period. This was attributed, in part, to a sampling change. The mortality footprint fell slowly in later periods – to 9.9 million ha in 2007-2011 and 6.9 million ha in 2012-2016. Other than during the 2002-2006 period, mortality was relatively low in the Northern Region – despite EAB – especially when compared to high mortality in the Rocky Mountain and Pacific Coast Regions attributed to bark beetles.

The mortality area attributed to pathogens was also highest in 2002-2006. This was due to three pests: a root diseases-bark beetle complex killing subalpine fir, oak wilt, and beech bark disease.

Very little disease mortality was reported in the South during any of the five-year periods – an alarming failure given damage to redbay by laurel wilt. The lapse is more confusing because past IDS reports have listed redbay as heavily damaged (see USDA FS FHTET 2014).

The Pacific states saw a modest increase over time. The sudden oak death infestation was first detected by the IDS survey in 2008 – approximately 13years after it was detected on the ground.

Over the 20 years, non-native species caused mortality on an average of 500,000 ha in each five-year period except 2002-2006 (described above). The proportion of the total mortality footprint associated with non-native species was14.8% in 1997-2001, 34.4% in 2002-2006, 3.6% in 2007-2011 & 7.4% in 2012-2016.

Only in the Northern Region was a large proportion of the mortality footprint consistently attributed to non-native species – 35.1% in 1997-2011 to 98.5% in 2002-2006. The suite of species changed over time. In the first period (1997-2001), the principal species were beech bark disease, European gypsy moth, oak wilt, and hemlock woolly adelgid. During two periods – 2002-2006 and 2007-2011 – those present earlier were joined by BWA, EAB, and Dutch elm disease. By the final period – 2012-2016 – the principal agents were EAB and red pine scale.

beech bark disease
Photo by Linda Haugen
courtesy of Bugwood

Non-native mortality agents detected in the South included hemlock woolly agelgid and oak wilt. HWA affected 71.8% of the affected area in 2006 – 2012, 21.9% in 2012-2016. EAB was first detected by the aerial survey in 2016.

In the two western regions, non-native agents had low footprints. The highest impacts were associated with BWA and white pine blister rust in the Rocky Mountain Region, Port-Orford cedar root disease and SOD in the Pacific Region, with the addition of BWA in some years and ROD in 2015 and 2016.

(All these pests are described here.)

Generally, woodborers have caused the highest mortality levels, seconded by pathogens. Only in the 2002-2006 period did another insect feeding guild exceed 10% of total mortality area – when BWA (a sap feeder) reached 18.7% of detected mortality – on balsam fir in Maine.

In the Western regions, the disease white pine blister rust was second to the subalpine fir mortality complex. Even this ranking fails to reflect widespread mortality of lower-elevation five-needle pines in previous decades.

In the Northern Region, a disease – beech bark disease – was most important in the first five-year period. It was replaced by a wood-boring beetle – EAB. I have noted the importance of the BWA (a sap-feeder) infestation during 2002-2006.

In the Southern Region, native bark beetles usually predominated. There were outbreaks of the foliage-feeding European gypsy moth in2007-2011 and hemlock woolly adelgid (sap-feeder) in 2012-2016.

The authors of the report note that the South might be underrepresented for several reasons – but without mentioning the severe impacts on the understory trees redbay and more recently sassafras.

SOURCES

Bailey, R.G.. 1995. Descriptions of the ecoregions of the United States. 2d ed. Miscellaneous Publication No. 1391. Washington, D.C.: U.S. Department of Agriculture Forest Service. 108 p.

Fei, S., R.S. Morin, C.M. Oswalt, and A.M. 2019. Biomass losses resulting from insect and disease invasions in United States forests

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

Morin, R.S., K.W. Gottschalk, M.E. Ostry, A.M. Liebhold. 2018. Regional patterns of declining butternut (Juglans cinerea L.) suggest site characteristics for restoration. Ecology and Evolution.2018;8:546-559

Morin, R. A. Liebhold, S. Pugh, and S. Fie. 2019. Current Status of Hosts and Future Risk of EAB Across the Range of Ash: Online Tools for Broad-Scale Impact Assessment. Presentation at the 81^st Northeastern Forest Pest Council, West Chester, PA, March 14, 2019

Potter, K.M., B.S. Crane, W.W. Hargrove. 2017. A US national prioritization framework for tree species vulnerability to climate change. New Forests (2017) 48:275–300 DOI 10.1007/s11056-017-9569-5

Potter, K.M., M.E. Escanferla, R.M. Jetton, and G. Man. 2019a. Important Insect and Disease Threats to United States Tree Species and Geographic Patterns of Their Potential Impacts. Forests. 2019 10 304.

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

USDA Forest Service. Forest Health Monitoring: National Status, Trends, and Analysis 2018. General Technical Report SRS-239. June 2019. Editors Kevin M. Potter Barbara L. Conkling

USDA Forest Service. Forest Health Technology Enterprise Team. 2014. 2013-2027 National Insect and Disease Forest Risk Assessment. FHTET-14-01

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

“Year of Plant Health” – Opportunity to Review International Phytosanitary Programs’ Effectiveness

The U.N. Food and Agriculture Organization has declared 2020 to be the International Year of Plant Health. APHIS, U.N. FAO, and others planned celebratory events — most now postponed.

The designation prompts consideration of whether the current global phytosanitary system – created in 1995 – is succeeding in preventing movement of invasive plant pests and invasive plants. Join me in this evaluation!

I focus on evaluating the most widespread invasive pests killing trees – and the pathways on which they travel. Some of the most damaging tree pests, of course, were moved around the world decades ago. But too many have been transported after the modern plant health system was developed in the mid-20^th Century with the adoption of the original International Plant Protection Convention (IPPC) in 1951.

Of course, this is also the period when trade volume exploded, resulting in new source countries, new products, and new technologies that facilitated newly rapid movement of goods and accompanying pests. See my earlier blog here and the book by Marc Levinson, The Box: How the Shipping Container Made the World Smaller and the World Economy Bigger. It is well-documented that rising trade volumes, new trade connections, new products have and will continue to exacerbate unintended movement of species (Seebens et al., 2018).

The phytosanitary regime was massively revised in the mid-1990s through adoption of the World Trade Organization and the Agreement on Sanitary and Phytosanitary Standards (SPS Agreement). Two principal changes were to constrain individual countries’ freedom to establish their own phytosanitary regulations and to require evidence of risk rather than allowing action on the basis of “if in doubt, keep it out”. I have written a critique of the new system in Fading Forests II. See Chapter 3, available here.

USDA officials burn infested cherry trees – gifts from Japan
Washington, D.C. 1912

Has the new regime allowed spread of pests, as I predicted in my critique?

Of course, the explosion of global trade has made prevention of species introductions far more difficult. So the rising numbers of introductions cannot be blamed entirely on the SPS Agreement. Still, it is vital to review pest status in order to see whether the SPS Agreement is succeeding in protecting Earth’s flora. Here, I am looking at only one type of bioinvader. Many more types need to be evaluated, even among plants and plant pests. Nor do I pretend that my list is comprehensive even in the category I focus on – tree-killing insects, nematodes, and pathogens.

My definition of “global invader” is an insect, pathogen, or nematode that has been moved from its known or probable place of origin to at least two novel continents or widespread island groups.

Before the SPS Agreement

Of course, many highly damaging forest insects and pathogens spread widely before the eruption of global trade in the second half of the 20^th Century. Examples include several pathogens:

American chestnut bred to be resistant to blight
photo by F.T. Campbell

Phytophthora cinnamomi – Europe, North America, Oceania, South America
Cryphonectria parasitica – Europe and North America; Oceania probably much later
Dutch elm disease causal agents Ophiostoma ulmi & novo-ulmi (the vectors are sometimes native insects) – Europe, North America, Oceania;

And some insects:

Hylastes ater – Oceania, South America, Africa
Scolytus multistriatus (Dutch elm disease vector) – North America 1909; later to Oceania; mid-20^th Century to Africa

There have also been initial introductions of some organisms that would become “global” later:

Phytophthora lateralis – North America before 1950

During the period 1950 – 1995 –when trade began exploding and countries were adopting their own phytosanitary regulations as allowed under the original IPPC – the following pests were introduced “globally”:

P. ramorum in Big Sur, California
photo by Matteo Garbelotto

Phytophthora ramorum was introduced from Southeast Asia to Europe and North America.
Hylurgus ligniperda – Oceania, South America, Africa, Asia after 1950; North America before 1995
Phoracantha recurva – detected in various geographies after 1995, but almost certainly introduced to North America, South America, Europe, Africa, and Oceania before that date
Palm pests – red palm weevil (Rhynchophorus ferrugineus) to most areas of the Old World and Oceania where palms grow; coconut rhinoceros beetle (Oryctes rhinoceros) around Africa, Mauritius, Reunion; Oceania;

Again, there were initial introductions of numerous insects in wood packaging and on “plants for planting” that would expand to “global” ranges after 1995:

Anoplophora glabripennis

To North America: Anoplophora glabripennis;, Agrilus planipennis; Austropuccinia psidii; Phoracantha recurve; Glycaspis brimblecombei
To Asia: Pine wood nematode Bursaphelenchus xylophilus
To Oceania, South America – Sirex noctillio;

After the SPS Agreement

There has been an apparent explosion of spread since adoption of SPS Agreement in 1995. No doubt these introductions were made possible by the concurrent explosion of trade volumes and more pest-friendly shipping practices (e.g., use of shipping containers and more rapid transportation). The principal vector appears to be plants for planting. About 50% of new plant pathogen invasions are associated with plants for planting (Jimu et al. 2016). Wood packaging is a strong second vector.

Tree-killing pests of which I am aware that have apparently spread globally after 1995 include:

Insects

Aulacaspis ysumatsui – North America, Caribbean, Pacific Ocean islands, Oceania, Africa, Europe, various islands off Southeast Asia that are probably outside original range

*Erythrina humeana* in the Manie van der Schijff Botanical Garden, Pretoria
vulnerable to Euwallacea / Fusarium complex

Quadrastichus erythrinae – North America, Southeast Asia, islands in the Indian and Pacific oceans

Euwallacea fornicatus complex, esp. Euwallacea whitfordiodendrus and E. kuroshio and their Fusarium symbionts Fusarium euwallaceae, Graphium euwallaceae, & Paracremonium pembeum – North America, Africa

Several insects that attack Eucalyptus have been widely introduced to areas where plantations of these species have been planted, e.g.,

Blue gum chalcid wasp or eucalyptus gall wasp Leptocybe invasa – throughout Africa, the Middle East, Asia, the Pacific Region, Europe, South America, Mexico, and the United States [CABI]
Red gum lerp psyllid (Glycaspis brimblecombei) Europe 2009 [EPPO]
Eucalyptus snout beetles Gonipterus spp complex à two species introduced to five continents (Schroder et al. 2019).
Eucalyptus gall wasp(Ophelimus maskelli) – Mediterranean Region, the Middle East, South Africa, Europe, U.S., New Zealand [CABI]

Continued spread of species that had been introduced to a single new continent before 1995:

Pine wood nematode Bursaphelenchus xylophilus – to Europe
Phytophthora lateralis – to Europe and South America
Myrtle rust Austropuccinia psidii – to Pacific oceanic islands and Oceania
Anoplophora glabripennis and A. chinensis – to Europe
Sirex noctillio – to North America
Agrilus planipennis – to Russia and western Europe
Red palm weevil (Rhynchophorus ferrugineus) – to North America (California- eradicated)
Coconut rhinoceros beetle (Oryctes rhinoceros) – to Pacific islands, e.g., Guam and Hawai`i

I note that several studies have identified large numbers of introduced species in certain categories, although the dates of introduction are uncertain. Some were probably introduced before 1995. Here I cite the following:

Jung et al. (2015) found 59 putative Phytophthora taxa in forest and landscape planting sites in Europe; none had been detected by inspectors at the European Union borders.
Jimu et al. (2019) report global spread of Eucalyptus pathogens carried by the trade in seed and cuttings to support establishment of new plantations and breeding programs.
Numerous species of Phytophthora across North America – about 60 species in California native plant nurseries; eleven species in Minnesota (both from Swiecki et al. 2018); Parke et al. (2014) identified 28 Phytophthora taxa in four Oregon nurseries.
Nine species of Phytophthora associated in urban streetscapes, parks, gardens, and remnant native vegetation in urban settings in Western Australia (Barber et al. 2013).

So What’s the Bigger Picture?

I have blogged frequently about the weaknesses of the international standard governing wood packaging; go here.

Clearly the weaknesses of the international phytosanitary system are not limited to the wood packaging pathway. And I repeat that the phytosanitary system is under severe challenge by trade volumes and practices – at least before the Covid-19 pandemic. Still, it is clear that the international phytosanitary system has failed in achieving its purpose: to provide adequate protection in response to this challenge.

I have two suggestions:

1) I hope that the most affected countries will take action per their authority under Section 5.7 of the SPS Agreement. This allows emergency action to prevent further introductions via the principal pathways and from the geographic origins posing the greatest threats (e.g., China for wood packaging, Southeast Asia for Phytophthora pathogens).

2) I hope further that all the nearly 200 countries that are parties to the SPS Agreement and the IPPC will rapidly institute an analysis of the current phytosanitary system to quickly identify amendments to the agreements that would better enable countries to protect their plants from non-native pests.

SOURCES

Barber, P.A., T. Paap, T.I. Burgess, W. Dunstan, G.E.St.J. Hardy. 2013. A diverse range of Phytophthora species are associated with dying urban trees. Urban Forestry & Urban Greening 12 (2013) 569-575

Jimu, L., M. Kemler, M.J. Wingfield, E. Mwenje, and J. Roux. 2016. The Eucalyptus stem canker pathogen Teratosphaeria zuluensis detected in seed samples. Forestry 2016 89 316-324 https://academic.oup.com/forestry/article/89/3/316/1749105

Jung, T., L. Orlikowski, B. Henricot, P. Abad‐Campos, A. G. Aday. O. Aguín Casal, J. Bakonyi, S. O. Cacciola, T. Cech, D. Chavarriaga, T. Corcobado, A. Cravador, T. Decourcelle, G. Denton, S. Diamandis, H. T. Doğmuş‐Lehtijärvi, A. Franceschini, B. Ginetti, S. Green, M. Glavendekić, J. Hantula, G. Hartmann, M. Herrero, D. Ivic, M. Horta Jung, N. Keca, V. Kramarets, A. Lyubenova, H. Machado, G. Magnano di San Lio, P. J. Mansilla Vázquez, B. Marçais, I. Matsiakh, I. Milenkovic, S. Moricca, Z. Á. Nagy, J. Nechwatal, C. Olsson, T. Oszako, A. Pane, E. J. Paplomatas, C. Pintos Varela, S. Prospero, C. Rial Martínez, D. Rigling, C. Robin, A. Rytkönen, M. E. Sánchez, A. V. Sanz Ros, B. Scanu, A. Schlenzig, J. Schumacher, S. Slavov, A. Solla, E. Sousa, J. Stenlid, V. Talgø, Z. Tomic, P. Tsopelas, A. Vannini, A. M. Vettraino, M. Wenneker, S. Woodward, A. Peréz‐Sierra. 2016. Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora disease. Forest Pathology. November 2015.

Levinson, M. The Box: How the Shipping Container Made the World Smaller and the World Economy Bigger Princeton University Press 2008

Schroder, M. Slippers, B., Wingfield, M.J., Hurley, B.P, Invasion history and management of Eucalyptus snout beetles in the Gopterus scutellatus species complex. 2019. Journal of Pest Science

Parke, J.L., B.J. Knaus, V.J. Fieland, C.Lewis, and N.J. Grünwald. 2014. Phytophthora Community Structure Analyses in Oregon Nurseries Inform Systems Approaches to Disease Management. Phytopathology Vol. 104, No 10.

Schroder, M. Slippers, B., Wingfield, M.J.,Hurley, B.P, Invasion history and managementof Eucalyptus snout beetles in the Gopterus scutellatus species complex. 2019. Journal of Pest Science

Seebens, H., T.M. Blackburn, E.E. Dyer, P. Genovesi, P.E. Hulme, J.M. Jeschke, S. Pagad, P. Pyse, M. van Kleunen, M. Winter, M. Ansong, M. Arianoutsou, S. Bacher, B. Blasius, E.G. Brockerhoff, G. Brundu, C. Capinha, C.E. Causton, L. Celesti-Grapow, W. Dawson, S. Dullinger, E.P. Economo, N. Fuentes, B. Guénard, H. Jäger, J. Kartesz, M. Kenis, I. Kühn, B. Lenzner, A.M. Liebhold, A. Mosen, D. Moser, W. Nentwig, M. Nishino, D. Pearman, J. Pergl, W. Rabitsch, J. Rojas-Sandoval, A. Roques, S. Rorke, S. Rossinelli, H.E. Roy, R. Scalera, S. Schindler, K. Stajerová, B. Tokarska-Guzik, K. Walker, D.F. Ward, T. Yamanaka, and F. Essl. 2018. Global rise in emerging alien species results from increased accessibility of new source pools. PNAS Plus. Available at http://www.nature.com/articles/ncomms14435

Swiecki, T.J., E.A. Bernhardt, and S.J. Frankel. 2018. Phytophthoraroot disease and the need for clean nursery stock in urban forests: Part 1 Phytophthora invasions in the urban forest and beyond. Western Arborist Fall 2018.

Wondafrash, M., B. Slippers, A. Nambazimana, I. Kayumba, S. Nibouche, S. van der Lingen, B.A. Asfaw, H. Jenya, E.K. Mutitu, I.A. Makowe, D. Chungu, P. Kiwuso, E. Kulimushi, A. Razafindrakotomamonjy, P.P. Bosu, P. Sookar & B.P. Hurley. 2020. Distribution and genetic diversity of five invasive pests of Eucalyptus in sub-Saharan Africa. Biological Invasions Vo. 22, pp. 2205-2221 (2020)

Coconut rhinoceros beetle – https://www.cabi.org/isc/datasheet/37974 + websites for Guam and Hawai`i

Red palm weevil – https://cisr.ucr.edu/invasive-species/red-palm-weevil

Posted by Faith Campbell

Money for Key Programs in FY2021 – 1st Round

Congress has begun work on funding the government for Fiscal Year 2021, which begins on 1 October 2020.

The House Appropriations Committee has adopted bills funding USDA APHIS (via the agriculture appropriations bill) and USDA Forest Service (via the interior appropriations bill). Both provide steady or increased funding for programs important to preventing, eradicating, containing, and managing non-native tree-killing pests.

However, the Senate must act also – and I don’t yet know whether it will support these spending increases — or even whether it will pass an appropriations bill.

Still – we should applaud members of the House Agriculture and Interior subcommittees for supporting these programs (go here to see if your representative is on the committees). The same link provides justifications for funding the various programs.

USDA APHIS funding for key programs

Program FY2020 Admin’s Request FY2021

APHIS Plant Protection

Ag Quarantine (appropriated) 32,330,000 33,350,000 33,070,000

Pest detection 27,446,000 27,967,000 37,824,000

Methods develop 20,686,000 21,045,000 20,946,000

Specialty crops 192,013,000 183,079,000 198,912,000

Tree & wood pests 60,000,000 56,336,000 60,600,000

In its report, the Appropriations Committee reiterated its longstanding instruction that the Secretary of Agriculture tap funds in the Commodity Credit Corporation to fund emergency actions to “arrest and eradicate” plant pests. The report also called for APHIS to maintain funding levels and cost-share requirements for addressing the Asian longhorned beetle. (I expect emergency funds will be needed to address the newly detected ALB outbreak in South Carolina.) The Committee noted that it had provided $4 million in additional funds to counter the spotted lanternfly outbreak.

In addition, the Committee instructed APHIS to work with the USDA Forest Service, National Institute of Food and Agriculture, and Climate Hub to assist U.S. tropical areas (Hawai`i, Puerto Rico, US Virgin Islands, Guam, Marianas) to address several issues, including:

Land and forest resource management; and
Biology and control of invasive insects, plant diseases, weeds and integrated pest management strategies;

Forest Service – funding for key programs

Program FY2020 Pres’ request FY2021

Research &

Development $305,000,000 $249,330,000 $311,830,000

State & Private

Forestry overall $346,990,000 $217,443,000 $300,296,000

Forest Health

Management $100,000,000 $84,636,000 $101,136,000

In its report, the Appropriations Committee said that it expected the USFS to develop a research program that reflects the committee’s priorities and other activities most critical to forest health, especially addressing climate change adaptation, preventing spread of disease and invasive species, and watershed improvement. The Committee also supported research on holistic approaches to countering the harmful effects of terrestrial invasive species, utilizing a coordinated approach that incorporates expertise in forestry, veterinary science, aerospace engineering, biotechnology, agronomy and applied economics.

Addressing the Forest Health Management program, the Committee report encouraged the USFS to address high priority invaders, including the emerald ash borer and native western bark beetles.

The bill also rejected the President’s proposal to eliminate the Urban and Community Forestry program. Instead, it provided $8 million above the FY2020 level (that is, $40 million); this total includes $2 million allocated to helping communities hard-hit by the emerald ash borer to replant their urban forests.

Now that the House has acted, the next step – usually – is for the Senate Agriculture and Interior appropriations subcommittees to mark up their own bills. However, those who follow Congress closely don’t expect the Senators to be able to reach agreement on spending levels. Instead, they expect, the Senate will pass a “continuing resolution” that maintains current funding levels for the various programs. Perhaps after the election, they might then adopt more detailed bills.

Please – if one of your Senators is on either of these subcommitees (see the lists here), ask him or her to support the House spending levels on these programs.

I have written extensive descriptions of the impact of funding inadequacies in Fading Forest III, available here.

Posted by Faith Campbell

For a detailed discussion of the policies, practices, and funding shortfalls 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

Why such scattershot responses to myrtle rust?

myrtle rust infestation;
source: New Zealand Department of Agriculture alert May 2017

Pacific countries’ policy and management responses to the spread of the myrtle rust pathogen, Austropuccinia psidii (formerly Puccinia psidii), has had puzzling – even infuriating – gaps … which perhaps have contributed to its spread and damage.

Reminder: ‘ōhi‘a or myrtle rust attacks species in the Myrtaceae – a family now said to include 5,600 species (Stewart et al. 2018). Ten percent of Australia’s native flora is in the family – or about 1,300 species. New Zealand is home to 27 native plants in the Myrtaceae family (Bereford et al. 2019) and the Hawaiian Islands to eight (JB Friday pers. comm.). See a writeup about the disease here.

Austropuccinia psidii is one of the global invaders: it has invaded 27 countries on several continents. It is apparently native to parts of the American tropics.

Levels of worry rose considerably with the pathogen’s spread across the Pacific beginning with the detection in Hawai‘i in spring 2005. Additional introductions in the region were Japan in 2009; China in 2011; Australia, New Caledonia, and South Africa in 2013; and New Zealand in 2017.

The known host range currently exceeds 500 species in 86 genera – all in the Myrtaceae family. The pathogen has several strains or biotypes; the impact of the various biotypes on the various host species differs. Environmental factors also apparently affect disease.

[For my earlier discussions of threats to the unique Hawaiian flora, go here for dryland flora, here and here for more general discussions. I discuss National Park Service efforts – including in Hawai`i – here.]

There are several factors that militate against a political entity choosing to act:

1) Inherent Difficulty in Controlling Wind-Borne pathogen

In both Hawai`i and Australia, the rust spread rapidly once it was established outside of nurseries. In Hawai`i, it had spread to all the islands within a few months of its detection in spring 2005 (Loope and La Rosa 2008). In Australia, the rust was established in natural ecosystems throughout coastal New South Wales and to far northern Queensland by mid-2012 – less than two years after detection (Carnegie et al. 2016). The number of host species also expanded rapidly – from 214 native plants in 2016 (Carnegie et al. 2016) to 393 species by 2019 (Winzer et al. 2019). Myrtle rust is believed to have been carried to Australia and New Caledonia on imported plants or cut vegetation; then to New Zealand by winds from Australia across the Tasman Sea (Toome-Heller et al. 2020).

2) Lack of Clarity About Probable Impacts

Austropuccinia psidii had been introduced fairly widely before 2000, and some biotypes had caused significant damage on introduced species within both the native and introduced ranges of the rust – e.g., Eucalyptus in Brazil, allspice (Pimento doica) in Jamaica, rose apple (Syzygium jambos) in Hawai`i. However, the rust had had little impact on native floras in introduced ranges, especially not on widespread species (Carnegie et al. 2016).

However, concerns existed in the Pacific region because of:

Its wide host range (before the introduction to Australia, the known host range was “only” 129 species in 33 genera Carnegie et al. 2016).
The severe damage to Australian genera growing outside their native range, e.g., nurseries and plantations of Eucalyptus in South America and Melaleuca quinquenervia and Rhodomyrtus tomentosa in Florida (Carnegie et al. 2016)

In Hawai`i, ‘ōhi‘a rust caused little damage to the dominant tree species in Hawaiian forests, ‘ōhi‘a lehua for the first 10 years after its introduction. The rust did cause severe damage to the invasive alien shrub rose apple and several native plants, especially the endangered Eugenia koolauensis. A more damaging outbreak in ‘ōhi‘a lehua trees in 2017 has increased concern.

ohia rust on E. kooaulensis
photo by Edward Eickhoff via Flickr

So – while Austropuccinia psidii has an extremely wide host range, its impact in naïve ecosystems to which it might be introduced is unclear.

In most cases, lack of knowledge about a pest’s impacts on naïve hosts in new ranges is almost inevitable – unless scientists undertake host vulnerability tests. Such tests are rarely done in advance of an introduction. One exception is European scientists evaluating European trees’ vulnerability to a suite of newly discovered Phytophthora species in Vietnam and elsewhere. (I am unaware that U.S. scientists are carrying out parallel studies.)

Still, environmental and other factors play important roles and might counter expectations raised by lab experiments or experience of hosts planted in non-native sites. In Australia, McRae (2013) noted that the “mycological firestorm” predicted by environmentalists to result from introduction of the rust had not occurred. This at least partly explained waning interest in combatting the pathogen (Carnegie et al. 2016).

In my view, the swings in perceptions of the risk reflected more flaws in understanding than actual risk. Impacts can take time to manifest – especially when, as with Austropuccinia psidii – the pathogen is known to affect primarily new growth and fruit and flowers (Carnegie et al. 2016). The impact might be greatest in the form of suppressing regeneration rather than by killing mature trees right away. [See beech leaf disease as another possible example of this phenomenon.]

Questions hampering predictions of impact were further confused by taxonomic questions (Carnegie et al. 2016). Austropuccinia psidii has at least nine genetically distinct clusters. So far, two have been introduced outside South/Central America. One strain – called the “pandemic biotype” – has been found at all introduction sites in Florida, Hawai‘i, Asia, and the Pacific – Australia, New Zealand, New Caledonia (Stewart et al. 2018). This biotype is not known to be present in Brazil (Toome-Heller et al. 2020). A second biotype has been introduced to South Africa; it has been shown to be able to infect some Myrtaceae in New Zealand (Toome-Heller et al. 2020). See especially Stewart et al. 2017, full citation below.

3) Policy Barriers Created by Phytosanitary Regulations

In the U.S., the pathogen has been established in one state – Florida – since 1977. There, it is not considered to be causing damage to important species. Under U.S. regulations – reflecting the international trade rules – an organism that is already in the country cannot be treated as a “quarantine pest” unless there is an “official control program” targeting the pest. (For a discussion of this issue, see the analysis of the SPS Agreement in Chapter 3 and Appendix 3 of Fading Forests II). For this reason, when ‘ōhi‘a rust was detected in Hawai`i in 2005, USDA’s Animal and Plant Health Inspection Service (APHIS) was unable to adopt regulations governing imports or interstate movement of vectors (i.e., cuttings or nursery stock of plant species in the Myrtaceae).

The State responded to the initial detection by adopting an emergency order two years later, in August 2007. This prohibited importation of plants in the myrtle family from “infested areas”- specified as South America, Florida, and California. This state rule expired in August 2008.

It became apparent that USDA APHIS would not take action to assist Hawai`i unless APHIS accepted scientific findings as proving that additional biotypes of the rust existed that could pose a more severe threat to plants on the Islands. Such studies were undertaken, some funded by the USDA Forest Service. This process took years. During this period, Hawai`i developed a permanent rule which was adopted in May 2020. This regulation restricts the importation to Hawai`i of plants in the Myrtaceae, including live plants and foliage used in cut flower arrangements. Dried, non-living plant parts, seeds that are surface sterilized, and tissue cultured plants in sterile media and containers are exempted from the ban. Other importations may be done by permit.

Meanwhile, in 2019, APHIS proposed to include all taxa in the Myrtaceae destined for Hawai`i in an existing regulatory category of “plants for planting” not authorized for importation pending pest risk assessment (NAPPRA). The intent was to reduce the probability of introduction of additional strains of Austropuccinia psidii to the Islands. This proposal appeared 14 years after the rust was first detected in Hawai`i. And the proposal has not yet taken effect. Therefore, imports of most living plants and cut foliage are still subject only to inspection (7 Code of Federal Regulations 319.37). The tiny size of the rust spores makes detection during inspection unlikely unless the plant is displaying symptoms of the disease.

Imports of logs and lumber involving tropical hardwood species (including Eucalyptus) into Hawai`i are regulated under separate provisions which have been in effect since 1995. The wood must be debarked or fumigated [Code of Federal Regulations – 7 CFR 319.40-5(c)]. Incoming wood packaging is regulated under ISPM#15; I think it unlikely that the treatments prescribed therein would kill any rust spores present.

Policy Responses in Other Vulnerable Countries

Australia

Austropuccinia psidii had been recognized as a potentially serious biosecurity threat to Australia as early as 1985 (publications cited by Carnegie et al. (2016). The introduction of ‘ōhi‘a rust to Hawai`i so alarmed plant health and conservation officials in Australia and New Zealand that they sent representatives half way around the world to participate in the North American Plant Protection Organization’s annual meeting in Newfoundland, Canada, in October 2007! Yet interest in Australia waned when large scale tree mortality and major impacts on industries did not immediately occur (Carnegie et al. 2016). The state of New South Wales listed the rust as a Key Threatening Process to the Natural Environment, but the federal agencies rejected a petition to do the same at a national level (Carnegie et al. 2016).

Groups of scientists are carrying out research with the goal of demonstrating that the rust is already having severe effects on key species in natural ecosystems, and probably significantly affecting a wider range of species (Carnegie et al. 2016; Winzer et al. 2019; Winzer et al. 2020)

In 2018 a scientist affiliated with the Australian Network for Plant Conservation published a draft conservation plan. Its development had input from staff at the Plant Biosecurity Cooperative Research Centre and the Australian Government Department of the Environment and Energy. The goal was to help direct and stimulate further research on critical questions and build awareness of the potentially devastating effects myrtle rust might have if it remains unchecked. As of April 2020, no funding had yet become available to finalize and implement the report (Dr Michael Robinson, Managing Director, Plant Biosecurity Science Foundation).

New Zealand

New Zealand has been more aggressive in its policy approach. It adopted a strategy when Australia announced arrival of the rust in 2010. The islands had bad luck – myrtle rust is believed to have been carried to New Zealand by wind from Australia across the Tasman Sea.

As soon as the rust was first detected in 2017, two government agencies initiated broad surveys of Myrtaceae across natural and urban areas, with active outreach to citizens (Toome-Heller et al. 2020). By April 2018, it was recognized that the pathogen was too widespread to be eradicated. Significant finds were made on the western side of the North Island and at the very northern tip of the South Island (see map in Beresford et al. 2019). At that point, the government changed its focus to long-term management of the disease.

A. psidii is still very much a focus for Maori (indigenous) groups, central and local government, community groups, Myrtaceae-based industries, and research institutions.

Several research programmes are currently looking for management options, including resistance breeding (Toome-Heller et al. 2020). See research plan and reports of results to date here. However, which plant species can become infected, and under what environmental conditions, remain unclear.

New Zealand researchers have made some findings that should be of concern to forest pathologists working with all Myrtaceae:

A. psidii can overwinter as a latent infection without reproducing.
A. psidii can reproduce sexually, although the importance of the sexual cycle in seasonal epidemic development is not yet understood and teliospores have only infrequently been found in New Zealand (Bereford et al. 2019).
the unique biotype found in South Africa has already been found to be pathogenic towards some New Zealand native Myrtaceae (Toome-Heller et al. 2020).

We can expect these finding to have implications for elsewhere, including in Hawaii.

Pathways of Introduction

It is thought probable that the rust was introduced to Hawai`i on cut foliage imported from Florida. The first Australian detection was at a cut flower facility (Australian Invasive Species Council).

CABI considers plants and plant parts (including cuttings, flowers, and germplasm) to be the principal pathway. Other pathways appear to be contaminated plant waste, timber, wood packaging and dunnage; and – over short distances – contaminated equipment and tools and clothing, shoes and other personal effects.

Conclusions

The saga of myrtle rust demonstrates both the biological and technical difficulties of controlling an airborne pathogen and the inability of the existing phytosanitary system to respond to new situations. Regulatory officials are obligated to demand levels of knowledge and certainty that just are not realistic. The gap is especially great at the crucial time – before an invasion or at its earliest stage — when phytosanitary actions might be most effective.

This saga also demonstrates that efforts often wane at the management and restoration stages. At least in Hawai`i and New Zealand, government resources are still being allocated to research possible resistance breeding or other possible long-term approaches. I refer you to the article by Enrico Bonello, me, and others about the need to provide sufficient resources to such efforts in the U.S.

Sources

Australian Invasive Species Council.2011. www.invasives.org.au Environmental impacts of myrtle rust Fact Sheet February 2011

Beresford, R., G. Smith, B. Ganley and R. Campbell. 2019. Impacts of myrtle rust in NZ since its arrival in 2017. 2019. New Zealand Garden Journal 2019, Vo. 22 (2). https://www.myrtlerust.org.nz/assets/news/NZ-Garden-Journal-Dec-2019-p5-10.pdf

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, and K.F. Wallin. 2019. Invasive tree pests devastate ecosystems – A proposed new response framework. Frontiers http://journal.frontiersin.org/article/10.3389/ffgc.2020.00002/full?&utm_source=Email_to_authors_&utm_medium=Email&utm_content=T1_11.5e1_author&utm_campaign=Email_publication&field=&journalName=Frontiers_in_Forests_and_Global_Change&id=510318

Carnegie, A.J., A. Kathuria, G.S. Pegg, P. Entwistle, M. Nagel, F.R. Giblin. 2016. Impact of the invasive rust Puccinia psidii (myrtle rust) on native Myrtaceae in natural ecosystems in Australia. Biological Invasions (2016) 18:127–144

Code of Federal Regulations. January 1, 2005 (Title 7, Volume 5). 7 CFR319.40-5: Logs, lumber, and other unmanufactured wood articles – importation and entry requirements for specified articles. (available by using search engines/retrieval services at http://www.gpoaccess.gov/fr/index.html).

Code of Federal Regulations. January 1, 2005 (Title 7, Volume 5). 7 CFR319.37: Nursery stock, plants, roots, bulbs, seeds, and other plant products – prohibitions and restrictions on importation: disposal of articles refused importation. (available by using search engines/retrieval services at http://www.gpoaccess.gov/fr/index.html).

Loope, L. and A.M. La Rosa. 2008. An Analysis of the Risk of Introduction of Additional Strains of the Rust Puccinia psidii Winter (`Ohi`a Rust) to Hawa`i. Pacific Island Ecosystems Research Center

Stewart, J. E., A. L. Ross-Davis, R. N. Graça, A. C. Alfenas, T. L. Peever, J. W. Hanna, J. Y. Uchida, R. D. Hauff, C. Y. Kadooka, M.-S. Kim, P. G. Cannon, S. Namba, S. Simeto, C. A. Pérez, M. B. Rayamajhi, D. J. Lodge, M. Agruedas, R. Medel-Ortiz, M. A. López-Ramirez, P. Tennant, M. Glen, P. S. Machado, A. R. McTaggart, A. J. Carnegie, and N. B. Klopfenstein. 2018. Genetic diversity of the myrtle rust pathogen (Austropuccinia psidii) in the Americas and Hawaii: Global implications for invasive threat assessments. Forest Pathology 48(1): 1-13. https://doi.org/10.1111/efp.12378

Toome-Heller, M. W.W.H. Ho, R.J. Ganley, C.E.A. Elliott, B. Quinn, H.G. Pearson, B.J.R. Alexander. 2020. Chasing myrtle rust in New Zealand: host range and distribution over the first year after invasion. Australasian Plant Pathology

Winzer, L.F., K.A. Berthon, A.J. Carnegie, G.S. Pegg, M.R. Leishman. 2019. Austropuccinia psidii on the move: survey based insights to its geographical distribution, host species, impacts and management in Australia. Biological Invasions April 2019, Volume 21, Issue 4, pp 1215–1225

Winzer, L.F., K.A. Berthon, P. Entwistle, A. Manea, N. Winzer, G.S. Pegg, A.J. Carnegie, M.R. Leishman. 2020. Direct and indirect community effects of the invasive plant pathogen Austropuccinia psidii (myrtle rust) in eastern Australian rainforests. Biological Invasions. Volume 22, pages2357–2369 (2020)