​​the states and nursery industry to ensure that living plants shipped from one part of the country to another are free of pests. APHIS should collaborate with the states, firewood industry, camping organizations, and others to ensure that firewood does not transport pests. APHIS, the states, woodworkers and the timber industry collaborate to ensure that logs they transport do not transport pests.   Success in preventing the introduction and spread of tree-killingpests depends on access to improved tools for finding, monitoring, and controlling the pests and for restoring tree species to the forest.  Therefore, CISP will also advocate for adequate funding for research and methods development programs carried out by APHIS, the USDA Forest Service, and other federal, state, and academic entities.


[1] 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)

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


Principal Pathway for Tree-Killing Pests: Wood Packaging
Decade-Old Policies Do Not Prevent Introductions

Despite regulations adopted at least nine years ago, tree-killing insects continue to enter the United States in wood packaging. Here we suggest how aggressive enforcement could protect our rural and urban forests from further huge ecological and economic losses.

Tree-Killing Pests Introduced via this Pathway

As Americans import more stuff, the risk of introducing damaging invasive species rises. Among the most frequently introduced are insect larvae hiding in wooden crates, pallets, etc. – called “solid wood packaging” or SWPM.

Over the last 30 years, at least 58 non-native species of wood- or bark-boring insects have been detected in the United States.[i] Two of them have caused enormous ecological or economic damage; two others threaten to cause even greater destruction. (For longer descriptions of each pest, visit the Gallery of Pests).The existing damage has been caused by

  • the emerald ash borer (EAB). Over about 25 years, the emerald ash borer has spread to more than 100,000 square miles in 25 U.S. states and two Canadian provinces. This spread has occurred despite a complex system of federal and state quarantines. It is already the most costly tree-killing insect introduced to the U.S. due to the high costs cities and homeowners face in removing dead trees and treating those that still live.[ii] 

  •  the redbay ambrosia beetle with an associated fungus. Over about 15 years, this beetle/disease complex has spread from North Carolina to eastern Texas.  It will probably nearly eliminate one host, the redbay tree, from the southeastern coastal plain before 2030.[iii]   Many trees and shrubs presumed to be vulnerable to the redbay ambrosia beetle grow in Central America, to which the disease is likely to spread.

Potentially greater harm could be caused by

  • the Asian longhorned beetle (ALB). Over the past 20 years, USDA APHIS has spent more than $500 million trying to eradicate the Asian longhorned beetle because it threatens trees growing on more than 10% of all U.S. forest lands, plus billions of trees in cities & suburbs.  While this extensive effort has not yet succeeded in eradicating ALB from North America, it has protected billions of trees that otherwise would be at risk.

  • the polyphagous and Kuroshio shothole borers (PSHB) and their associatedFusarium fungus are established widely in eight counties in southern California. They feed on more than 300 types of woody plants;  more than 100 of these support reproduction of the disease complex. At particular risk are boxelder, sycamore, cottonwoods, and willows. It is not yet known how many of these trees and shrubs can be killed by the disease … but the insect can reproduce in five types of maples, Many of the vulnerable tree species are important components of riparian communities in southern California. Collectively, these tree taxa make up more than half of trees planted in urban areas in southern California. Despite the on-going damage and threat, neither APHIS nor the California Department of Food and Agriculture has adopted programs aimed at containing the invasive shot hole borers. In 2018, the state legislature enacted a measure to initiate a program. Several vulnerable trees are also either native to forests in the southeast – e.g., box elder and sweetgum; or have close relatives in those forests – other maples, oaks, hollies, coral tree, willows … Since both insects are from Southeast Asia, wood packaging from this region transported to the Gulf Coast could introduce this highly damaging disease complex to that region. Widening of the Panama Canal has increased the risk as more ships will arrive from Asia to our east coast ports.

Current Policy Still Allows Tree-Killing Pests To Be in SWPM

USDA APHIS began requiring debarking of wood packaging with the aim of preventing insect infestation in 1995. In 1998, due to detections of the Asian longhorned beetle (see above), APHIS required Chinese exporters to treat wood packaging by heating it or applying pesticide. Since 2006, the U.S. and Canada have required wood packaging accompanying imports entering the country from all countries to be treated according to the International Standard on Phytosanitary Measures (ISPM)#15.  For a description of how ISPM#15 was negotiated, its strengths & weaknesses, read the Fading Forests reports.

However, 16 years after China was required to treat its wood packaging, and nine years after similar requirements were applied to nearly all trade partners, tree-killing pests still infest a small proportion of incoming wood packaging. Probably 13 million or more shipping containers that include wood packaging enter the country each year. As many as 17,600 containers harboring pests probably enter the country each year – or 48 each day. [iv]   The Asian longhorned beetle is among the pests still detected in wood packaging from China. [v] 
Cities that import the most goods from Asia are at particular risk. These include some you would expect: New York, Chicago, Los Angeles and Long Beach. Others might surprise you:  Washington, D.C.;  Virginia Beach; Jacksonville. [to see a more complete list, view the Continental Dialogue's fact sheets.

What the Government Has Done

USDA APHIS persuaded the Justice Department to prosecute a US wood packaging manufacturer who fraudulently claimed that its crates and pallets complied with the international standard; the company was fined $100,000. APHIS also collaborated with its Canadian counterpart to sponsor a workshop on compliance with the standard in Asia; they hope to schedule additional workshops in other regions (visit www.nappo.org to learn more about the workshop).  

But neither action directly addresses the issue of incoming wood packaging transporting pests.

What More Can be Done: Close the Pathway

  • Until November 2017, both APHIS and the Bureau of Customs and Border Protection allowed an importer to be caught 5 times in 1 year with wood packaging that did not comply with the regulatory requirements. This leniency is inappropriate given that the requirements have been in place for a dozen years for imports from most countries, for 18 years for imports from China! 
    In November 2018, the Bureau of Customs and Border Protection adopted a new policy under which it may penalize any importer whose wood packaging does not comply with regulatory requirements.  APHIS has not changed its policy; it still will not consider imposing a penalty until a specific importer has been detected in violation of the regulations four times in one year.
  • Most major U.S. importers have joined a voluntary program with the Bureau of Customs and Border Protection called “Customs-Trade Partnership Against Terrorism” (C-TPAT). Under this program, the importers closely monitor their foreign suppliers through all steps in the supply chain – production, storage, and transport – of the goods they are importing. In return, CBP processes their imports more quickly. CBP should incorporate the wood packaging treatment requirements in the C-TPAT program.
  • USDA APHIS should re-examine the economic pros and cons of requiring importers to switch to packaging made from alternative materials rather than wooden boards. The new review should incorporate the high economic and ecological costs imposed by just a few of the dozens of insects introduced via the wood packaging pathway.

  • Currently, the U.S. and Canada do not require that wood packaging moving between the two countries comply with the international standard. This policy not only exposes un-invaded portions of both countries to damaging pests established in the other country (for example, ALB or EAB), it also undermines efforts to ensure that all North American packaging sent overseas complies with the standard. USDA APHIS should work with the President’s Office of Management and Budget to finalizing regulations – proposed in 2010! – that would apply ISPM#15 to wood packaging in trade between the US and Canada. (Canada has been ready to adopt this measure for several years.)


[i] Leung, B., M.R. Springborn, J.A. Turner, E.G. Brockerhoff. 2014. Pathway-level risk analysis: the net present value of an invasive species policy in the US. The Ecological Society of America. Frontiers of Ecology 12: 273-279.

[ii] Herms, D. A. and D. G. McCullough. 2014. Emerald Ash Borer invasion of North America: History, biology, ecology, impacts, and management. Annual Review of Entomology, Vol 59, 2014 59:13-30; 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 6(9):e24587.

[iii] United States Department of Agriculture Forest Service. Forest Health Technology Enterprise Team. 2014. 2013-2027 National Insect and Disease Forest Risk Assessment. FHTET-14-01

[iv] Haack RA, Britton KO, Brockerhoff EG, Cavey JF, Garrett LJ, et al. (2014) Effectiveness of the International Phytosanitary Standard ISPM No. 15 on Reducing Wood Borer Infestation Rates in Wood Packaging Material Entering the United States. PLoS ONE 9(5): e96611. doi:10.1371/journal.pone.0096611, Data updated based on personal communication from Customs and Border Protection. 

[v] Haack, R.A., F. Herard, J. Sun, J.J. Turgeon. 2009. Managing Invasive Populations of Asian Longhorned Beetleand Citrus Longhorned Beetle: A Worldwide Perspective. Annu. Rev. Entomol. 2010. 55:521-46; these authors report six separate introductions; after the article was published, a seventh was detected in Clermont County, Ohio; and a new outbreak was detected near Toronto, Ontario. Also, Philip Berger, Executive Director
PPQ Science and Technology, Presentation to the Continental Dialogue on Non-Native Forest Insects and Diseases,November 3, 2014


Sudden Oak Death: Current Regulatory Situation

Sudden oak death (SOD) is a disease caused by a brown alga. The disease is known to infect more than 100 species of plants, including California bay laurel (Oregon myrtle), camellias, Douglas-fir, hemlock, huckleberries, larch, lilacs, Pacific madrone, magnolias, maples, mountain laurel, oaks, redwoods, rhododendrons, and viburnums. Many of these hosts are popular ornamentals that are shipped long distances by numerous nurseries. This creates potential opportunities for the disease to spread quickly and widely.

 USDA’s 2014 Regulations


In early 2014, USDA APHIS [link] amended its regulation governing movement of nursery stock potentially infested with SOD. [go here to read APHIS’ 2014 SOD rule] 

 The 2014 program focused regulatory efforts on the highest-risk nurseries, thereby reducing costs for both regulatory agencies (APHIS and its state counterparts) and nurseries. Under the 2014 regulations:

Nurseries in California, Oregon, and Washington that ship SOD host plants interstate are now subject to APHIS regulation only under the following conditions:

  • the SOD pathogen has been detected in the nursery at least once over the past three years (the three-year window is a “rolling” window, continually updated; the initial starting date was  March 31, 2011); and
  • the nursery ships plants interstate. (Before, all nurseries from these states that ship host plants interstate were subject to APHIS rules on inspection and certification);

Exception: nurseries in counties where sudden oak death is established in the wild remain under federal inspection and certification requirements regardless of whether they have previously tested positive for the pathogen; 14 California counties and one in Oregon are affected.

Nurseries in other states will be subject to the revised regulation only if they ship SOD host plants interstate and the pathogen has been detected at the nursery over the past three years (again, this three-year window is a “rolling” window).

The types of samples to be evaluated have been greatly expanded. In the past, only plants were tested, now samples will also be taken from nurseries’ soil, standing water, drainage water, irrigation water, growing media, and other articles.

Any nursery that ships host plants interstate and in which the SOD pathogen has been detected, regardless of location, must enter into a compliance agreement with APHIS. The agreement requires the nursery to adopt mitigation measures to address sources of the pathogen present in the nursery. Thus, adoption of a critical control point approach is mandatory.

Nurseries that have tested “clean” over the same “rolling” or continually updated three-year period are now exempt from the federal inspection and certification requirements.

In August 2018, APHIS proposed revisions to the 2014 regulation. The agency’s stated goal was to provide regulatory relief to West Coast nurseries that have not recently been found positive for P. ramorum while ensuring that the nursery trade does not spread the disease. The proposal’s components would formalize steps taken in a series of Federal Orders issued over the past decade. In its comments, CISP objected that APHIS should not simply formalize existing practices but instead should strengthen the regulatory system by regulating all nurseries that ship P. ramorum host plants – regardless of their location or history of disease presence. Furthermore, inspections should be based on sampling and testing of soil, growing media, and water, rather than on visual inspection of plants. Finally, APHIS should update its list of host plant species (which dates to 2012). All the comments are available here

The best sites for learning about sudden oak death/Phytophthora ramorum and related issues are

  •  the California Oak Mortality Task Force website and monthly newsletter
  •  APHIS' chronology


For a lengthy description of the threat from forest pests and analysis of current policies' efficacy, read the Fading Forests reports available here. Go here to obtain several 2-page fact sheets that describe the pathways by which forest pests enter the U.S. or are spread within the country; economic impacts of these pests; and responsibilities of federal agencies. 

Photo of wood packaging from which beetle larvae was extracted; used with permission of Oregon Department of Agriculture

What Can We Do? 

To prevent tree-killing pests’ introduction and spread, CISP advocates for the following actions:   APHIS should tighten its regulations on wood packaging and imported plants to minimize the number of  pests that use these pathways to reach the U.S. American companies should hold their foreign suppliers responsible for complying with conditions under which wood packaging and plants may be shipped to the U.S. APHIS and the Bureau of Customs and Border Protection should vigorously enforce requirements that ships from Asia be free of gypsy moth eggs. APHIS should collaborate with

How do tree-killing pests reach North America?  

The insects and plant pathogens that are killing North America’s trees reach here primarily as larvae or spores riding undetected in several kinds of imports: 

  • Crates, pallets, and other kinds of packaging made of wood. 
  • Living plants imported for our use, often as ornamentals in our gardens.
  • Decorative items made of wood  

Asian gypsy moths and their relatives also arrive as egg masses attached to the ships themselves.    

Photo of ash tree killed by emerald ash borer which has fallen on house is from Ann Arbor, MI; used with permission of Mayor Hieftje

The U.S. government has worked for a century to prevent introduction and spread of damaging plant pests, including those which attack trees.  These programs are administered primarily by a branch of the U.S. Department of Agriculture, the Animal and Plant health Inspection Service (APHIS). (APHIS' responsibilities are described briefly under "Invasives 101" on this website.) Despite APHIS’ efforts, tree-killing pests continue to arrive in the U.S.  New introductions are occurring at approximately two new pests each year. Since the beginning of the 21st Century, at least 30 new species of insect or pathogen that attacks native trees have been detected in the country [2].  What kind of damage do they cause? Non-native pests have nearly eliminated the American chestnut from the eastern forests, where it once made up almost a quarter of the trees.  Several other tree species, including Port-Orford cedar, western white pine,  whitebark pine, eastern and Carolina hemlocks, Fraser fir, and redbay have been severely reduced over most of their ranges. Seventeen species of ash trees across the continent are threatened.  Oak trees in California are under attack by three different pests. Several of Hawai`i’s unique trees and shrubs are also under siege.   


The highest costs arise from cities’ efforts to manage their dead and dying trees. Local governments across the country spend an estimated $1.7 billion each year to remove trees killed by the emerald ash borer or other pests. Homeowners spend an additional $1 billion to remove and replace trees.  In addition, they lose $1.5 billion per year in value of their property. These amounts will rise substantially as the emerald ash borer and other pests continue to spread.[1]  For more information about individual pests, visit www.dontmovefirewood.org and click on “Gallery of Pests”.  

Non-Native Forest Insects and Diseases

Since European settlement began in North America, nearly 500 non-native tree-feeding insects and disease-causing pathogens have been introduced into the United States. About 80 of these have caused notable damage to our trees.   As the map illustrates, the highest numbers are in the Northeast, upper Midwest, and Mid-Atlantic.  However, the Pacific Coast states are catching up and every county has at least 3 damaging non-native pests.

Map updated from that published in Liebhold, A.M., D.G. McCullough, L.M. Blackburn, S.J. Frankel, B. Von Holle, J.E. Aukema. 2013. A highly aggregated geographical distribution of forest pest invasions in the USA. Diversity and Distributions. (2013) 1-9