Insects & Pathogens Introduced Via Plant Imports – Let’s Collaborate to Understand Risk


map showing locations in Hawaii Volcanoes National Park of ʻōhiʻa infested by rapid ʻōhiʻa death; NPS map available here

The U.S. Department of Agriculture’s adoption of a new list of plant species barred from importation pending pest risk assessment after a four-year wait (NAPPRA) [see my previous blog from June 21, here] prompts me to review what I know about pests associated with plant imports – and to appeal for collaboration among non-USDA scientists to improve our understanding of current  risks. Therefore I’m sharing some pest import and establishment data. I welcome the opportunity to work with experts to evaluate the level of risk and other matters that might be extracted from these data. Contact me to explore how we might work together.

As was pointed out by Eschen et al. 2015 (see list of sources at the end of this blog), most countries’ data on the “plants for planting” pathway are inadequate to allow an assessment of phytosanitary measures’ efficacy in preventing pest introductions. The authors stressed the need for data on:

  1. plant imports at the level of genus, including plant type and origin;
  2. pest arrival rates on each of these categories of plant imports; and
  3. pest establishments.

In the apparent absence of agencies’ efforts to close these data gaps, I propose that we work together, using available information, to improve our understanding of the current level of risk. Perhaps we can agree on which pest species are real red flags; decide which pathways most need new policy approaches; and reach conclusions about the implications of holes in the data.

  1. What Do We Know About Plant Imports?

The U.S. imports approximately 2.5 billion plants each year. The plants most likely to transport insects or pathogens that would attack North American trees and shrubs are woody plants. According to Rebecca Epanchin-Niell, during the period FY2010-FY2012, Americans imported each year more than 300 million woody plant units, belonging to about 175 genera.

Marcel Colunga-Garcia and colleagues analyzed plant import data for the period 2010-2012. They studied maritime (ship-borne) containerized plant imports, which represented 64.4 percent of the total value of all “plants for planting” imported into the U.S. in 2010, excluding imports from Mexico and Canada. The types of plants shipped in this way include rooted plants in pots; bare root plants; bulbs and tubers; root fragments, root cuttings, rootlets or rhizomes; rooted cuttings; unrooted cuttings; and budwood/graftwood.

Measuring by the plants’ import values, Colunga and colleagues determined that New York and Los Angeles metropolitan areas together import 60 percent of these plants; not all plant imports are routed through Miami – as is often assumed.

Second, these data show which states are the ultimate destination for relatively large volumes of certain types of plants. Thus, the top five states for receipt of rhododendrons and azaleas were Michigan, Oregon, California, New York, and New Jersey. Michigan received almost twice as many plants (measured by value) as New Jersey. The top three states for receipt of “fruit and nut trees and shrubs” were Florida, Louisiana, and Washington – all at nearly $1 billion or higher. California and North Carolina ranked fourth and fifth, but at values of only $200,000. It is clear from these data that contaminated plants could deliver pests virtually anywhere in the country.

Because my focus is on insects or pathogens that threaten native trees, I wish to separate those from pests that attack primarily herbaceous plants. (Of course, herbaceous plants are important components of ecosystems, as well as premier agricultural and horticultural crops! I do not mean to imply that pest threats to herbaceous plants are not important.)

About nine million of the 300 million woody plants imported to the U.S. each year belong to genera which also contain species of trees native to North America. A larger number of plants – 224 million – were in the same family as a North American native tree (Epanchin-Niell 2017). In other words, about 75% of the woody plants imported each year were in the same family as at least one species of tree native to North America.

Since plants in the same genus are more likely to transport damaging pests that would attack North American trees and shrubs, some have suggested that all such imports should be prohibited temporarily, using the NAPPRA process.

  1. What Do We Know About Pest Arrivals? (Including Detection Difficulties)

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 — a pathway that has received far more international and U.S. regulatory attention for years. This finding is similar to that of a study in New Zealand, which found that 14 percent of consignments of plants were infested – primarily with pathogens (Epanchin-Niell 2017). Worse, though, Liebhold et al. found that a high percentage of pests associated with a plant shipment is not detected by the inspectors, although APHIS has disputed this finding.


At my request, APHIS analysts compiled a list of imported woody plant genera on which pests were detected during fiscal years 2011-2016. Of the 360 quarantine pests listed, only 34 were designated as “disease” (nine percent of the total). I suspect this is significantly below the actual number entering the country.


Table 1. Overall number of pest detections recorded*

Fiscal Year # of records # of countries of origin for shipments found to be infested
2011 133 16
2012 110 14
2013 42 12
2014 27 9
2015 45 12
2016 14 5


* My totals do not include shipments from Puerto Rico; there were six pest detections on plants from the Commonwealth.

I cannot explain why the total number of detections shown in Table 1 nor – especially – the number of countries from which these infested shipments arrived fell so dramatically in FY2016. If APHIS was focused on inspecting the highest-risk shipments in FY15 and FY16, shouldn’t the number of interceptions have risen?


Pathogens are probably undercounted in Table 2 because inspectors experience great difficulty in detecting pathogens during port-of-entry inspections. For example, the genus Phytophthora does not appear in the database of port interceptions, yet we know that Phytophthora are being introduced. Also, the database does not contain the genus Rhododendron. It seems unlikely that no quarantine pests were detected on a shipment of Rhododendron over that six-year period.


Table 2. Types of Pests Intercepted

Disease                        34

Insect                           290

Mite                             20

Mollusk                       23

Nematode                    2



APHIS’s interception records are not designed as a statistically valid sample for determining the total number of pests on shipments because, for example, inspection priorities and resultant inspection criteria  change over time. Since 2015 APHIS has focused more on higher-risk shipments. Before, a specified percentage of all imports was inspected. For these reasons, interception records cannot be used to evaluate the overall risk of pests being imported along with “plants for planting” in any given year. Nor can APHIS’ interception records be compared over time.

Obviously, the numbers of pests detected on a specific type of import will reflect several factors, especially the volume of imports and the intensity of inspection. This bias in the data is reflected in the high number of pest interceptions from Central American countries – from which the U.S. imports very large volumes of plants. Two hundred twenty of the 385 pest detections recorded over the six-year period (57 percent) were on plants shipped from Costa Rica or Guatemala. Canada ranked third, with 35 pest detections (nine percent of the total).

That said, each record reflects a detection of a taxon of animal or pathogen that APHIS considers to be a “plant pest”. Each time a particular species is detected in a shipment, it is recorded. If more than one species is detected in a shipment, each species is reported separately. Therefore,

  • the number of detection records does not equal the number of shipments found to be infested;
  • the records do not reveal the number of specimens of each named taxon – either in an individual shipment or in total; and
  • the number of times a taxon appears in the database does indicate how many shipments were found to be infested by that taxon.



  1. Principal Threats to North America’s Native Trees and Shrubs

APHIS and I agree that our focus should be on those pests likely to have significant consequences if they are introduced. This risk of impact depends on climate, presence of probable hosts in the U.S., and other factors. Among the highest risk sources of imports for most the U.S. will be temperate countries, like those below. APHIS assigns a lower rating of risk to pests that are likely to be established in the U.S. already or to establish naturally – e.g., pests native to northern Mexico near the U.S. border.


Table 3. Main Temperate Countries of Origin for Infested Shipments by Year

FY2011:  Germany, Japan, Turkey, Netherlands, France, Pakistan, Canada, New Zealand

FY2012:  Israel, Canada, South Korea, China, Chile, Netherlands

FY2013:  France, Canada, Belgium, China

FY2014:  China, Canada, South Africa, Portugal

FY2015:  China, Germany, Netherlands, Canada, France, Australia

FY2016:  Canada



We can also look at the host plants on which pests are being intercepted to think about threats. Table 4 shows these. Presumably, the volume of trade in these genera, from the countries concerned, is sufficient to preclude any listing of these hosts under the NAPPRA regulatory process (see blog from June 21).


Table 4. Host Genera on which Pests Were Intercepted, Including only Genera Native

to North America or U.S. Islands or Important in Ornamental Plantings

 Plant genus                 # records — countries of origin — types of pests

Acer                             7 — primarily Canada; also Netherlands & Korea – 2 disease, 4 insect, 1 mite

Buxus                           3 – all Canada – 2 insect, 1 mollusk

Camellia                      2 – France – 1 disease, 1 mite

Chamaecyparis                        1 – Canada; mite

Cycas revoluta             8 – Honduras, Costa Rica, Dom. Rep. – insects

Fagus                          6 – Netherlands, Belgium; insects (aphids primarily)

Hibiscus                       4 – France, Tahiti, Canada – 1 disease, 1 insect, 1 mite, 1 mollusk

Ilex                              3 – Canada & NL – 2 insects, 1 disease

Liriodendron               2 – Canada – insects

Magnolia grandifolia  1 – South Africa – insect

Opuntia                       6 – Mexico – insects

Picea                           7 – Canada – insects (primarily aphids)

Thuja                           6 – Canada – insects

Tilia                             2 – Canada – mollusk


  1. What Else Do We Know?

If we look at pests introduced via all pathways, unlike those above, U.S. pest-establishment data show that plant pests continue to be introduced, but at a slower pace in recent years. In its Implementation Plan for Section 10201 of the Food, Conservation and Energy Act of 2008, USDA APHIS said that between 2001 and summer 2008, 212 pests were reported as new to the United States – an average of 30 new pest introductions each year. An APHIS database of plant pests “newly detected” during fiscal years 2009 – 2013 listed approximately 90 new taxa of plant pests as detected during this period – approximately 22 each year. In its annual report for 2016, the agency reported detecting 16 species of plant pests not previously detected in the U.S.

I think that approximately 37 of the 90 “new” pests detected over the 2009-2013 period were probably introduced via imports of plants, cuttings, or cut foliage or flowers. These include all the viruses, fungi, aphids and scales, whiteflies, and mites. I have asked APHIS to give me a database of newly detected plant pests for fiscal years 2014-2015, but the agency has not done so.

Among tree-killing pests introduced over the past 160 years, approximately 69% were introduced via the live plant trade. Liebhold et al. 2012 found that 95% of sap feeders, 89% of foliage-feeding insects, and 47% of pathogens were introduced via this pathway.

Pathogens are probably undercounted here, too, since those that do not cause massive damage are probably overlooked. Of the approximately 90 pests newly detected  2009-2013, ten were fungi, four were viruses, and two were rusts (18 percent of the total).

The genus Phytophthora does not appear in the database of “newly detected” pests. Yet we know that Phytophthora are being introduced. We know that, in 2012 a Phytophthora new to the United States — Phytophthora tentaculata — was detected on nursery-raised herbaceous plants in California. Follow-up studies have detected several additional Phytophthora taxa that might be new to the United States. One, P. quercina, had previously been reported only in Europe and Western Asia. The other putatively new taxa are still being evaluated as to whether they are previously unknown species or hybrids, and whether they are native to California or elsewhere in the United States, or are of alien origin.


The presence of the EU1 strain of Phytophthora ramorum in several nurseries in Washington, California, and most recently Oregon is also evidence that introductions of this species have continued since it was designated as a regulated pest in 2003.


Another pathogen that has apparently not been included in the official data is the fungus which causes rapid ʻōhiʻa death – a strain of Ceratocystis fimbriata. Scientists do not yet know whether this strain was introduced directly to Hawai`i on a recently-imported, asymptomatic plant; or whether the strain evolved from one or more different strains introduced to Hawaiʻi recently or longer ago.


Can you help evaluate the level of risk associated with various plant taxa, types, and origins? and other matters that might be extracted from these data. Perhaps we can agree on which pest species cause greatest concern; decide which pathways most need new policy approaches; and reach conclusions based on holes in the data. Can we use the data on pest taxa that underlie this summary – data which I have – to strengthen the case for USDA to promptly finalize revision of its “plants for planting”  (“Q-37”) regulations (see my blog from June 21 and Chapter 4 of the Fading Forests report?


Contact me to explore how we might work together.


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.




Colunga-Garcia M, Haack RA, Magarey RD, Borchert DM (2013) Understanding trade pathways to target biosecurity surveillance. In: Kriticos DJ, Venette RC (Eds) Advancing risk assessment models to address climate change, economics and uncertainty. NeoBiota 18: 103–118. doi: 10.3897/neobiota.18.4019


Epanchin-Niel, R.S. 2017. Presentation to 28th USDA Interagency Research Forum on Invasive Species. January 2017.


Eschen, R., K. Britton, E. Brockerhoff, T. Burgess, V. Dalley, R.S. Epanchin-Niell, K. Gupta, G. Hardy, Y. Huang, M. Kenis, E. Kimani, H.-M. Li, S. Olsen, R. Ormrod, W. Otieno, C. Sadof, E. Tadeau, M. Theyse. 2015. International variation in phytosanitary legislation and regulations governing importation of plants for planting. Environmental Science and Policy 51 (2015) 228-237

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



Surprise! USDA Through APHIS moves on NAPPRA regulations


USDA headquarters; F.T. Campbell

To my complete surprise, USDA APHIS has finalized a four-year-old proposal to temporarily prohibit importation of 56 taxa of plants: 22 that are likely to be invasive and 34 that are hosts of eight insects, pathogens, or other types of plant pests.

On June 19, APHIS published a notice in the Federal Register announcing that APHIS had finally acted on a proposal initially published on May 6, 2013. To view the datasheets APHIS prepared and the comments APHIS received, go here.

Under APHIS’ regulations in ‘‘Subpart— P4P’’ (7 CFR 319.37 through 319.37–14 …), APHIS prohibits or restricts the importation of “plants for planting” – living plants, plant parts, seeds, and plant cuttings – to prevent the introduction of “quarantine pests” into the US. A “quarantine pest” is defined in § 319.37–1 as a plant pest or noxious weed that is of potential economic importance to the United States and not yet present in the country, or is present but is not widely distributed and is being officially controlled.

Section 319.37–2a authorizes APHIS to identify those plant taxa whose importation is not authorized pending pest risk analysis (NAPPRA) in order to prevent their introduction into the United States. As regards plant taxa that have been determined to be probable invasive species, such importation is restricted from all countries and regions. For taxa that have been determined to be hosts of a plant pest, the list includes (1) names of the taxa, (2) the foreign places from which the taxa’s importation is not authorized, and (3) the quarantine pests of concern.

The plant taxa now regulated because they host various types of plant pests are listed in two parts.

1) Species designated during the first round of action were proposed in 2011 and finalized in 2013 =

2)  Species proposed in 2013 and finally designated on June 19, 2017 =


In summary, the second round of NAPPRA seeks to prevent introduction of the following specific pests by prohibiting imports of their associated plants from most countries. Imports from Canada are often excepted and those from the Netherlands less often.

  • Asian longhorned beetle (ALB, Anoplophora glabripennis) – Celtis, Cercidiphyllum (katsura), Koelreuteria, Tilia
  • Great spruce bark beetle (Dendroctonus micans) – Pseudotsuga
  • Japanese pine sawyer (Monochamus alternatus) – Cedrus
  • Phytophthora kernoviae 17 genera, including Camellia, Fagus, Hedera, Ilex, Leucothoe, Liriodendron, Magnolia, Pieris, Quercus, Rhododendron, Sequoia, Vaccinium
  • Boxwood blight (Puccinia buxi) – Buxus (boxwood)


There are other restrictions on plant imports related to pests, which predate the most recent NAPPRA listing. These include =

  • Acer is already listed on the previous NAPPRA list for all countries except Canada, Netherlands, and New Zealand.
  • Longstanding regulations prohibit the importation of Abies species from all countries except Canada. The genera Larix, Picea, and Pinus were added to the NAPPRA list in the April 2013 NAPPRA notice.
  • Camellia was also listed in 2013 from all countries, except Canada, to prevent introduction of the citrus longhorned beetle (CLB, Anoplophora chinensis); the genus is also regulated for Phytophthora ramorum. The most recent action now adds restrictions because Camellia is also a host of Phytopththora kernoviae. Plants from Canada are exempt because of longstanding “significant trade” volumes.
  • While plants in the genus Cercidiphyllum (katsura) may be imported from the Netherlands – despite the presence in the country of both ALB and CLB – a 2013 Federal Order (DA–2013–18) specifies mitigation actions which exporting countries must take to prevent transport of these insects via trade in this or other genera.
  • Hedera was added to the NAPPRA list via the first round of proposals in April 2013 as a host of CLB. Under the 2013 proposal, the genus is also listed as host of Phytophthora kernoviae.
  • Vaccinium are consistently exported only from Canada and Australia. The genus is listed because it is a host of Phytophthora kernoviae.

As APHIS notes in its explanation in the Federal Register, P. kernoviae has been reported in England, Ireland, and New Zealand; APHIS considers this to be evidence of spread of the pathogen through the global movement of plants. APHIS notes further that the pathogen has a large number of confirmed hosts and there is currently no effective control measure. APHIS does not note that the native range of P. kernoviae is unknown.

APHIS received considerable pushback on its proposal to restrict importation of Callistephus, Chrysanthemum, and Eustoma spp. to prevent introduction of several pathogens, including chrysanthemum stem necrosis virus (CSNV) and chrysanthemum white rust.  In response, APHIS has withdrawn these three genera from the new NAPPRA listing while it conducts a commodity import evaluation document (CIED) for Chrysanthemum.


I have not discussed here NAPPRA as it applies to invasive plants. In April I blogged about the need for APHIS to act. Plants listed because of their invasive potential are posted here =

1) 2013 listing:

2) 2017 listing:

Again, I welcome USDA’s finalization of this second round of regulations and look forward to new proposals.


History of NAPPRA

In December 2004 APHIS published in the Federal Register an Advance Notice of Proposed Rulemaking, or ANPR which outlined a strategy for reducing pest introductions via the “plants for planting” pathway. The strategy had two major steps.

First, the agency would create a temporary holding category for plants suspected of transporting insects or diseases. This would allow APHIS to suspend imports of particular plants, from certain countries, until a full risk assessment was completed.

Second, APHIS would issue regulations establishing a general framework to minimize the presence of pests. Using this, the agency would negotiate country-specific requirements for imported plants, working toward an approach that would rely on “integrated measures” (also called “integrated pest management”).

APHIS formally proposed to create the temporary holding category – the NAPPRA program – in 2009. The regulations were finalized in May 2011 – six and one half years after the intention to take this action was announced in the ANPR. In adopting the NAPPRA rule, APHIS reiterated the need to encourage, but not require, the plant import trade either to rely on low-risk plant materials or to adopt pest-reduction methods.

In July 2011, APHIS published the initial list of species proposed for inclusion in the NAPPRA category.  This list was finalized in April 2013. A second list of species proposed for NAPPRA listing was published in May 2013.

This history – with citations – can be found in chapter 4, “Invasion Pathways”, in my report Fading Forests III, available here.


Meanwhile, here are a few related FAQs about NAPPRA as it is being implemented.


Why does APHIS regulate by genus?

APHIS regulates pests’ hosts at the genus level because when a new species is identified as a host, additional scientific studies often identify other host species within that genus. Therefore, regulating all species within the genus is the preferred course of action until a formal Pest Risk Analysis (PRA) is conducted. Uncertainties are worked out then.


How do these new rules fit into international standards?

APHIS notes in the Federal Register notice that  the “plants for planting” pathway is recognized as posing a high risk  for the introduction of pests. For this reason, the International Plant Protection Convention recommends that countries require a pest risk analysis before allowing importation of a plant taxon from a new country or region.


How long is importation of plants prohibited?

NAPPRA listing does not prohibit the importation of taxa indefinitely. Imports are held up until a pest risk analysis can be conducted to identify appropriate mitigation measures. Furthermore, an importer may apply for a controlled import permit to import small quantities of a prohibited or restricted taxon for developmental purposes.


What is the meaning of “significant trade”?


If a taxon that is a host of a quarantine pest has been imported in ‘‘significant’’ quantities from a specific exporting country, it is not eligible for the NAPPRA prohibition. Currently APHIS defines “significant trade” as the importation of 10 or more plants of a taxon in each of the previous three fiscal years. At the urging of one commenter, APHIS is considering whether to alter that definition by looking at import volumes over three out of five years – although the agency said if it took that action, it would most likely also consider raising the base number of plants from 10 to a higher level.


In the case of “significant trade” in a taxon that is a host of a quarantine pest, APHIS specifies other measures to address the pest risk.


What other protections does APHIS use?

A “Federal order” is used to rapidly take action to prevent the introduction of a quarantine pest, and is generally followed by notice and an opportunity for public comment. This is a separate action from the NAPPRA process.




The Overhaul of Regulations for “Plants for Planting (P4P) (the “Quarantine-37” or “Q-37” regulations) – Will It Also Be Finalized?


Another important APHIS action aimed at improving control over introductions of pests on imported plants has also been unresolved for four years. This is the revision to the agency’s overall plant import regulations, which was also proposed in May 2013. The revision would restructure the current regulations by moving specific restrictions on the importation of taxa from regulations to the Plants for Planting Manual. That transfer would allow specific restrictions to be changed without going through the full public notice and comment process required for amending formal federal regulations. The proposed revision would also add a framework for requiring foreign plant suppliers to implement integrated pest management measures to reduce pest risk. Experts believe that depending on integrated measures will better prevent pest introductions than the current reliance on a visual inspection at the time plants are shipped.


Again, for a history of and rationale for the proposed regulatory change, read chapter 4, “Invasion Pathways”, in my report Fading Forests III, available here.


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.


Status of Phytopthoras in the United States & Europe: an update

tanoak killed by sudden oak death; Marin County, Calif. photo F.T. Campbell

Here is some interesting information from recent issues of the the California Oak Mortality Task Force’s bimonthly newsletter. I am updating my earlier blogs on the status of Phytophthoras and sudden oak death (SOD) in the United States and Europe.


More than 600 samples were taken from streams or ponds in nine states (Alabama, Florida, Georgia, Mississippi, North Carolina, Pennsylvania, South Carolina, Tennessee, and Texas) during 2016. Ten of the samples were positive: seven from three streams in Alabama and three from one stream in Mississippi. Each of these had tested positive before; none was a new positive location. [March newsletter]


  • The disease continues to spread in Oregon and California:

During 2016 and early 2017, sudden oak death and tanoak mortality continued to intensify within the officially designated quarantine zone in southwest Oregon. So far, no new outbreaks have been detected outside the quarantine zone.

In Oregon, there is growing concern about the disease and the paucity of funds to address it. As a result, Oregon state Representative David Brock Smith and U.S. Senator Jeff Merkley have formed an Oregon Sudden Oak Death Task Force. The Task Force is developing a collaborative action plan to secure enough funding to contain the infestations of the NA1 genetic strain (the one widespread in Oregon and California) and to eradicate the EU1 lineage (this is the only known site where this strain is established in the forest in North America; see my blog from August 2015, which explains the significance of these strains.)  [March newsletter]


In California, scientists have been surprised by the intensity of the disease in several parks on the eastern side of San Francisco Bay – an area that is drier than most forests that are infested. The severe drought of recent years has not prevented spread of the disease. Even more surprising, one park has very little California bay laurel – which is considered to be the primary source of infection. [March newsletter]


  • Native plant nurseries may be spreading various Phytophthoras (see my blog from last year here) or the presentations on “Phytophthora Detections in Native Plant Nurseries and Restoration Sites” posted here)

The National Ornamentals Research Site at Dominican University (NORS-DUC) sampled several types of native plant nurseries in fall 2016 to determine the extent of movement of Phytophthora species on plants they sell. Unfortunately, the report in the newsletter did not include results of the sampling. [January 2017]

CFDA photo of herbaceous plants with Phytophthora infection

Oregon and Washington authorities acted in response to the initial reports from the San Francisco area, and sampled nurseries in their states. They found a similarly high infestation rate in native plant nurseries in their states. Washington State University and Oregon State University have held several 2 ½-day workshops on “Preventing Phytophthora Contamination in Native Plant Nurseries and Restoration Sites”. [May newsletter]

For more information about Phytophthoras in native herbaceous plants in California, visit  and

  • Disease costs in England and Wales could top 1 billion dollars


Drake and Jones have estimated that damage by Phytophthora ramorum and P. kernoviae [link to Gallery] to non-extractive public use and non-use values at risk from uncontrolled spread of these diseases in England and Wales is £1.446 billion per year (approximately $US 1.82 billion). The greatest public value at risk (slightly more than one-third) is from an uncontrolled spread of these diseases to heritage gardens; lower risks are to the diseases’ spread to woodlands and heathlands. [March newsletter]


5) Ireland resembles Europe in numbers of Phytophthora species:


O’Hanlan and colleagues tested more than 11,000 samples from both “trade” environments (presumably, nurseries) and “non-trade” environments (presumably plantings or natural environments). They detected 19 species and 3 informally designated taxa of Phytophthora, including 8 new records for Ireland. Thus, Ireland’s situation is similar to that in Europe more broadly – a study last year by Junker and colleagues report the detection of 15 Phytophthora species in two commercial woody ornamental nurseries [link to blog about Phythophs in Europe] In Ireloand, P. ramorum was found on 30 hosts; P. syringae on 6 hosts; P. kernoviae on 3 hosts. Phytophthora species were most frequently detected on rhododendrons – (12 Phytophthora species). [January newsletter]




Drake, B. and Jones, G. 2017. Public Value at Risk from Phytophthora ramorum and Phytophthora kernoviae Spread in England and Wales. Journal of Environmental Management. 191: 136–144.


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


O’Hanlon, R.; Choiseul, J.; Corrigan, M.; Catarame, T.; and Destefanis, M. 2016. Diversity and Detections of Phytophthora Species from Trade and Non-Trade Environments in Ireland. EPPO Bull. 46: 594–602. DOI: 10.1111/epp.12331.



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.


Lobby House and Senate Agriculture Appropriations Subcommittees in support of increasing funding for two crucial APHIS programs


On May 19 I posted a blog asking you to lobby Congress in support of maintaining current funding levels for two programs aimed to eradicating or containing tree-killing pests.  These are the “tree and wood pest” and “specialty crop” programs operated by the USDA Animal and Plant Health Inspection Service (APHIS).

At the time, I had not seen the President’s budget proposal. Now I have seen the President’s budget – and, as anticipated, it calls for steep cuts in the “tree and wood pest” program. The President calls for cutting this program by 44% — from $54 million to $30 million. Specifically, the Asian longhorned beetle (ALB) eradication program would be cut by approximately 50% — $20.770. The emerald ash borer (EAB) containment program would also be cut by half — $3.127 million.

The President’s budget justifies these severe cuts by saying that states, localities, and industries benefit from eradication or containment of the ALB and EAB, so they should help pay for the containment program.  The Office of Management and Budget states that other beneficiaries should pay 50% of program costs.

For whatever reason, the budget does not propose to cut APHIS’ efforts to prevent spread of the European gypsy moth.

In reality, states, localities, and industries are very unlikely to make up the difference in funding. We should remind the Congress that already, local governments across the country are spending more than $3 billion each year to remove trees on city property killed by non-native pests. Homeowners are spending $1 billion to remove and replace trees on their properties and are absorbing an additional $1.5 billion in reduced property values and reducing the quality of their neighborhoods. (See Aukema et al. article listed below.)

ash tree killed by EAB; Ann Arbor, MI; courtesy of Major Hefje


Cuts of the size proposed by the President’s budget will undermine the programs completely. Such a result is particularly alarming given the record of success in eradicating ALB populations – when resources are sufficient; and the urgent need to complete eradication programs in Massachusetts, New York, and Ohio. As I said in May, the ALB program has succeeded in eradicating 85% of the infestation in New York. (APHIS has just announced that a section of the borough of Queens is free of ALB.) However, the infestation in Massachusetts has been only 34% eradicated; that in Ohio has been only 15% eradicated. Crippling the program now will expose urban and rural forests throughout the Northeast to severe damage by this insect, which attacks a wide range of species.

The importance of continuing the EAB containment program has been re-emphasized by scientists’ recent determination that EAB can attack commercial olive trees as well as all species of ash.

The budget also does not recognize the need for APHIS to expand its program to address other tree-killing pests, including the spotted lanternfly, and polyphagous and Kuroshio shot hole borers.The shot hole borers attack hundreds of tree species, including California sycamore, cottonwoods, and several oaks. Many known hosts are either found across the Southeast, or belong to genera that are found across the Southeast – so the threat is national. The spotted lanternfly – now established in Pennsylvania — threatens agriculture – especially grapes, apples, plums, cherries, peaches, nectarines, apricots, and almonds; as well as oak, walnut, poplar, and pine trees.

More than 30 tree-attacking pests have been introduced in recent years. Additional species from these introductions might also require APHIS-led programs; one example is the velvet longhorned beetle.

velvet longhorned beetle;

The budget calls also for a 6% cut on the “specialty crops” program – from $158 million to $148 million.  It is not clear how such a reduction would affect APHIS’ program to prevent spread of the sudden oak death (SOD) via movement of nursery stock [link to earlier blogs & Gallery]. The SOD program has been funded at approximately $5 million in recent years.

Finally, additional challenges lie ahead because it is likely that new tree-killing pests will be introduced with rising import volumes. Each year, border inspectors detect more than 800 import shipments with pests infesting the crates and pallets. These represent a small proportion of the actual risk; one analysis estimated that 13,000 shipments with infested packaging enter the country each year. APHIS must have sufficient resources to respond when the inevitable newly introduced pests are detected.

CBP agriculture specialists in Laredo, Texas, examine a wooden pallet for signs of insect infestation. [Note presence of an apparent ISPM stamp on the side of the pallet] Photo by Rick Pauza

Aukema, J.E., B. Leung, K. Kovacs, C. Chivers, K. O. Britton, J. Englin, S.J. Frankel, R. G. Haight, T. P. Holmes, A. Liebhold, D.G. McCullough, B. Von Holle.. 2011. Economic Impacts of Non-Native Forest Insects in the Continental United States PLoS One September 2011 (Volume 6 Issue 9)

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.

Plan to Join the Continental Dialogue in Savannah, Georgia, in November 2017!

Spread of laurel wilt since 2003; source: USFS

Redbay mortality, Claxton, GA 2009

photo by Scott Cameron

The southeastern states have been invaded by a smaller number of non-native, tree-killing insects and pathogens than some other regions (see map below). But among these are highly damaging pests that show just how vulnerable this area’s native species and forests are, e.g., chestnut blight, laurel wilt, hemlock woolly adelgid, balsam woolly adelgid, and now emerald ash borer (all described here).

Join the Continental Dialogue on Non-Native Forest Insects and Diseases at its annual meeting in Savannah, GA, November 9 & 10, 2017 to learn about the issues outlined below and to build relationships to sustain action. The meeting will be in conjunction with the Annual Gypsy Moth Review, so we will also discuss the most recent developments pertaining to European and Asian gypsy moths. Visit to see the agenda and registration information (both to be posted soon).

The Southeast is at high risk for greater damage because:

  • The Port of Savannah is already the largest container port on the East Coast. Now, it moves 20,000 shipping containers per day and it is adding infrastructure to increase this volume.

Most of these containers – and their accompanying wood packaging material (for more on the risk from wood packaging, see my blog from the end of January; and fact sheets here) quickly move to distribution centers or their ultimate destinations – throughout the Southeast but as far away as Chicago. However, the port has storage for millions of containers on paved container yards that total 1,200 acres.  The storage yards are close to mixed forests.

Trees across road from stored containers at Port of Savannah;  photo by F.T. Campbell

More of these ships and containers will come directly from Asia – the major source of our most damaging invaders — now that the Panama Canal has been widened. When I visited the port in mid-May, the largest container ship ever to visit the U.S. East Coast was being unloaded – and re-loaded simultaneously!  The “Cosco Development” carries 13,200 TEUs (twenty-foot equivalent containers).

Unloading “Cosco Development” at Port of Savannah; photo F.T. Campbell

  • The sudden oak death pathogen (Phytophthora ramorum) has been found in streams and ponds in several southeastern states – Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, and Texas. Positive samples were drawn from three streams in Alabama and one stream in Mississippi in 2016. Most of these water bodies are near nurseries that had received infested plants from West Coast suppliers. In addition, infested plants have been detected recently in nurseries or landscape plantings in Louisiana, Texas, and Virginia, as well as in other states farther north [link to 2015 blog]. These infested plants have been removed. What is the current scientific thinking about the implications of these detections? Last I heard, scientists thought the pathogen cannot survive in water; it needs some plant material. Yet scientists have not found on-going infestations on plants along the streams and ponds. For more information on SOD, visit


  • Over recent decades, a half dozen non-native insects that attack pine trees have become established in the continental United States. These include the Sirex woodwasp, common pine shoot beetle, golden (or red) haired pine bark beetle (Hylurgus ligniperda), Mediterranean pine shoot beetle (Orthotomicus erosus) — all described here. The mountain pine beetle (Dendroctonus ponderosae) has spread east of the Rocky Mountains and might eventually reach pine forests of the Midwest and East.


While none of these (other than the mountain pine beetle) has yet caused very much damage where they are established, should we continue to assume that they will not cause damage once they reach the “pine basket” of the Southeast? Even if plantations can be managed to minimize risk, what are the implications for natural pine forests so important to the ecosystems and protected areas of the region?


It is unclear whether the fact that the Secretary of Agriculture, Sonny Perdue, is a former governor of Georgia with a record of support for forestry will raise attention to some of these issues.  As you might remember (see my blog from March 28th), apparently no senators raised invasive pest issues during Secretary Perdue’s confirmation.

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.