The native hardwood trees of southern California are under threat from several non-native insects and insect/pathogen complexes. I provided some recent information on one of these, the Kuroshio shot hole borer, in April; and a description of Californians’ efforts to counter the threat in August of last year. I think it is time to provide a more comprehensive update on the species.
I have blogged several times about the damage being caused to riparian trees in southern California by the polyphagous and Kuroshio shot hole borers – collectively referred to as the “invasive shot hole borers” or ISHB.
One of the most interesting sources of information about the shot hole borers are the series of visual surveys carried out by Orange County Parks under the leadership of Cathy Nowak (who has now retired). The most recent surveys were conducted in spring 2018 while deciduous trees were still dormant, so those estimates are based on the number of beetle gallery holes detected. An estimated 52,000 trees in the County’s parks are infested by either PSHB or KSHB. Eight regional parks and one historic house were surveyed. Only one large park remains uninfested. Comparing the results in 2018 to those of earlier surveys showed that percentages of host trees (in which the beetle can reproduce) that are infested rose over 2 years or less in seven of the parks – from a 9% increase in one park to a five-fold increase at another park with very low numbers of trees and low overall infestation rate earlier. The second highest increase is 89%.
The most heavily hit hosts are species long recognized as hosts See writeup on the borers here. Those with infestation rates exceeding 70% in one or more parks were
Acacia sp
Alnus rhobifolia (white alder)
Baccharis salicifolia (mule fat)
Erythrina caffra (coral tree)
Koelreuteria bipinnata (Chinese Flame tree*)
Koelreuteria paniculata (golden raintree)
Liquidambar styrachiflua (sweetgum)
Parkinsonia aculeate (palo verde)
Platanus occidentalis (American Sycamore)
Platanus racemose (California sycamore)
Platanus x hispanica (London plane)
Populus fremontii (Fremont cottonwood)
Populus trichocarpa (black cottonwood)
Quercus robur (English oak)
Salix spp. (willow)
* Chinese flame trees support ISHB only within cankered wood – other parts of the tree excrete thick gumming sap that protects.
Current information supports the vulnerability of California sycamore, and guidance that those seeking to learn whether the beetles have established should focus their surveys on sycamores.
As I have noted numerous times, several reproductive hosts are widespread in other parts of the country and could presumably support infestations there. These include box elder (not included in the Orange County surveys), sweetgum, and two magnolias – southern magnolia (M. grandiflora) and sweet bay (M. virginiana). Thirty-eight percent of the Magnolia grandiflora in one park were infested, although none was in three other parks. Koelreuteria spp. are a widely planted exotic across the country – although their role in spreading the disease appears to be limited by fact that they support ISHB development only in cankered wood. Birches have not been determined to be reproductive hosts, although one birch tree in one park had insect exit holes. Casuarina cunnninghamiana is also not known to be a reproductive host; trees in this genus are widespread invaders in Florida.
The good news is that none of a total of 12 southern live oaks (Quercus virginiana) growing in three parks had been attacked.
The goldspotted oak borer attacks California black oak, coast live oak, and canyon live oak. It is now widespread and continuing to spread in San Diego County. Officials report that is now established in more than 10 parks in the County.
There is a heavy GSOB infestation in Idyllwild, on the eastern edge of Riverside County. This outbreak is clearly linked to importation of infested firewood. Due to the heavy 2017 fire season, planned removal of “amplifying” trees (heavily infested trees that support large numbers of reproducing beetles) did not occur – and the outbreak is growing. Trees in the San Bernardino National Forest are at risk; 13 were removed in 2017.
In Los Angeles County, so far only one site has been infested – Green Valley (which includes both private land and nearby portions of the Angeles National Forest). An estimated 50,000 oaks are in the area. Officials are removing the “amplifier” trees; they expect they might have to remove close to 3,000 trees at a cost of $6 million. Officials are also treating some trees.
A newly detected heavy infestation has been detected at campgrounds in the Trabuco Ranger District in the Cleveland National Forest. Forest Service officials are debating management options, with an eye to protecting as many coast live oaks as possible. They have had success in the past by treating some trees with chemicals.
Meanwhile, scientists will be trying to evaluate the effect of fire since the 2017 fires burned several infested areas, e.g., Weir Canyon in Orange County.
The principal management strategy is to identify and remove heavily infested “amplifier” trees. The wood and bark must be disposed of properly and quickly – if the wood is left on the ground over night, people take it – thereby spreading the insects. High-value trees that are not heavily infested can be protected by application of the topical contact insecticide Carbaryl on the lower trunk. Officials are also experimenting with oak restoration using either planting of acorns or promoting root sprouting of trees that have had to be cut down.
Thousand Cankers Disease
Thousand cankers disease of walnuts is very widespread throughout California, but it is not causing widespread rapid tree deaths. Juglans californica has multiple stems. If one is killed, the others usually survive. The impact on J. hindsii is greater because it has a single stem and is grown as a street tree. California officials last conducted a survey of walnuts in the state in 2015, at the height of the drought. They appear to be confident that the age of this survey has not affected their assessment of the risk.
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.
As the federal government continues to dawdle in responding to invasive species challenges, some states are ramping up their efforts in significant ways.
California: New Legislation Creates a Program – but Only for One Year
The California state legislature has created a new invasive species program that focuses on those bioinvaders that threaten native ecosystems and the urban environment. It thus addresses some of the criticisms that I have previously levelled at the California Department of Food and Agriculture (CDFA) [see my earlier blogs here and here]
The new program has been established for one year; it will have to be renewed by the legislature next year.
The program results from adoption of legislation that combines what were initially two bills:
Assemblyman Timothy Grayson introduced AB 2470. This bill provided a legal foundation for the California Invasive Species Council and its Invasive Species Advisory Committee. It also provided funding for early detection and control projects targetting high-priority species, including weed management areas; and for supportive research and diagnostics work by the University of California.
Assemblywomen Lorena Gonzalez-Fletcher introduced AB 2054 focused specifically on the invasive shot hole borers [see descriptions of the polyphagous and Kuroshio shot hole borer here https://www.dontmovefirewood.org/ ]. The “Protect California Trees with Shot Hole Borer Beetle Prevention” (1) established a framework for a coordinated statewide effort; (2) instructed the Invasive Species Council of California and the California Invasive Species Advisory Committee to coordinate with state and local agencies and stakeholder groups to develop a plan to suppress the disease spread by this beetle.
The final legislation provided the full $5 million for addressing the shot hole borer but cut funding for the other components of the combined programs to just $2 million (so, a total of $7 million).
State officials have begun developing a shot hole borer management plan; they are expected to get input from a subcommittee by the Invasive Species Advisory Committee. The Advisory Committee held a meeting in mid-July to begin carrying out its coordinating functions.
Congratulations and thanks go to John Kabashima, who retired from his position as extension horticultural advisor with the University of California’s Division of Agriculture and Natural Resources. John has devoted two years to building the alliances needed to make this happen.
Minnesota: New Funding for Research
In 2014, the Minnesota legislature created the Minnesota Invasive Terrestrial Plants and Pests Center at the University of Minnesota. The Center applies science-based solutions to protect the state’s terrestrial ecosystems and agricultural resources. It utilizes an allocation from the Environment and Natural Resources Trust Fund to support a competitive research grant program. The current funding level is $3.5 million. Recently funded projects include evaluating the role of fungi in protecting ash trees from emerald ash borer and disease, genetic control of invasive insects, and use of goats in invasive plant control
The Center’s draft list of priority insects, plant pathogens, and invasive plants includes numerous forest pests. Among the 40 insect species listed, 19 are forest pests. Those in the top ten include mountain pine beetle, emerald ash borer, European and Asian gypsy moths, two elm beetles, and Asian longhorned beetle. Nineteen of 39 plant pathogens are tree-killers. Among the top ten are Dutch elm disease, oak wilt, Japanese oak wilt, Annosum root rot, sudden oak death, thousand cankers disease, and white pine blister rust.
In both cases, the lists include species that are already present and those not yet in the state (or even on the continent).
Western Governors’ Association: Initiative on Biosecurity
Incoming chairman, Hawaiian Gov. David Ige, has announced a Biosecurity and Invasive Species Initiative. The Initiative will focus on the impacts that invasive species have on ecosystems, forests, rangelands, watersheds, and infrastructure in the West, and examine the role that biosecurity plays in addressing these risks. Governor Ige hosted a webinar on 12 July [not yet posted on the WGA website] on which he was joined by such experts as Chuck Bargeron, Center for Invasive Species & Ecosystem Health, University of Georgia; Pam Fuller, Program Leader, Nonindigenous Aquatic Species Database, USGS; Stinger Guala, Director of Biodiversity Information Serving Our Nation (BISON), USGS; Jamie Reaser, Executive Director, National Invasive Species Council; and Lori Scott, Interim President & CEO, and Chief Information Officer, NatureServe. The Association is sponsoring regional workshops on various components of the invasive species response on the following dates
Lake Tahoe, NV Sept 17-18 – prevention, control, management of established species
Cheyenne, WY Oct 11 -12 – restoration
Helena, MT Nov 14 – early detection and rapid response
Hawai`i Dec 9 & 10 – biosecurity and agriculture
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.
There is widespread agreement that the most important pathways for long-distance transport of non-native forest insects are wood packaging (crates, pallets, dunnage, etc.) and imports of live plants (which APHIS calls “plants for planting”). Sources (at end of blog): Aukema et al. 2010; Liebhold et al. 2012; Meurisse et al. 2018 and many others. See also my earlier blogs by scrolling down to the “categories” section and clicking on “wood packaging”.
According to Meurisse et al., by the middle of this decade, world maritime freight trade had reached about 10 billion metric tonnes, and air transport of cargo had reached 50 million tonnes – much of it packaged in wood.
As the world’s biggest importer, the United States receives about 27 million shipping containers each year (CBP to FT Campbell). A study carried out in 2005 – 2007 (Meissner et al. 2009) indicated that 75% of maritime shipments entering the U.S. contained wood packaging; 33% of air shipments contained wood packaging. These are significant increases over earlier estimates that put the number of containers entering the country at 25 million. An even older analysis estimated that 52% of incoming containers had wood packaging.
APHIS has recognized the pest risk associated with wood packaging for 20 years – since the Asian longhorned beetle was detected in a second city – Chicago – in 1998. APHIS and its Canadian counterpart (Canadian Food Inspection Agency) acted rapidly to adopt, first, domestic regulations governing wood packaging from China (in December 1998), then a regional standard for wood packaging, and finally to help bring about adoption of International Standard for Phytosanitary Measures (ISPM) No. 15 in 2002. A detailed description of these actions can be found in my report Fading Forests II available here.
However, as I have demonstrated often, ISPM#15 has reduced the threat – but insufficiently. Dr. Robert Haack and his coauthors (2014) found that of each thousand shipments containing wood packaging that enters the country, one harbors a quarantine pest. Applying this estimate to the current volume of incoming containers and the higher proportion containing wood packaging results in an estimate that up to 20,000 shipping containers containing infested wood packaging enter the country each year – or approximately 55 per day.
The actual approach rate might be less. There are two variables that I lack sufficient data to quantify.
First, a significant proportion of the incoming containers come from Mexico or Canada – our second and third largest trading partners. The risk of damaging pests arriving from our neighbors is less than the risk accompanying shipments from overseas – although it is not “0”. Several woodborers native to Mexico have been introduced to U.S. ecosystems and are killing trees in these new environments, e.g., goldspotted oak borer, walnut twig beetle, and soapberry borer (all described in write-ups here). It is true that these beetles were probably introduced to vulnerable parts of the U.S. in firewood rather than wood packaging. There are also reasons to be concerned about pest introductions from Canada. Threats arise from both non-native pests established in the country e.g., brown spruce longhorned beetle and European beech leaf weevil, and pests in shipments from off-shore origins that are re-packaged in Canada (Yemshanov et al. 2012 and my earlier blog from April 2017).
The second variable on which I lack data is the proportion of the 27 million containers that are transported by air, and are thus half as likely to contain wood packaging.
To account for these unknowns, I have nearly halved the number of shipping containers likely to transport pests from off-shore – so 14 million instead of 27 million. Again applying Haack’s estimate, the result is 10,500 shipping containers containing infested wood packaging entering the country every year – or approximately 29 every day.
Update with more precise data (August 24) :
Re: the two variables, I have found partial answers from a U.S. Department of Transportation website which provides data on imports of loaded chipping containers (in TEUs) for 68 ports. (For the website, go here – click on “trade statistics”, then “US Waterborne trade” (1st bullet)]
As of 2017, 22,360,941 loaded shipping containers entered the U.S. via maritime transport. Applying the estimate of 75% of these containers holding wood packaging, we find that slightly less than 17 million containers entered the country with wood packaging. Applying Robert Haack’s estimate that one in a thousand is infested with a quarantine insect, we anticipate that 17,000 of these containers were transporting a pest that threatens our country. That is 46 containers every day.
Ports which received the largest numbers of containers, according to the DoT database:
Long Beach/Los Angeles — 8.4 million containers
New York — 3.4 million containers
Savannah — 1.8
Norfolk — 1.2
Houston — 1 million containers
We need answers!
The point is, we don’t know how many pests are reaching the United States daily. Or if the current approach rate is significantly higher or lower than in the past. Despite my urging, APHIS has not undertaken a study to update Haack’s estimate – which is based on 2009 data. In the intervening nine years, several changes were made to ISPM#15 to make it more effective. The most important was restricting the size of bark remnants that may remain on the wood.
Also, we might hope that experience with implementing the standard has led to better compliance. Unfortunately, available data do not encourage belief that compliance has improved.
Customs and Border Protection (CBP) reports annually to the Continental Dialogue on Non-Native Forest Insects and Diseases on the number of import shipments with wood packaging that have been detected as not complying with ISPM#15. Over a period of eight years – Fiscal years 2010 through 2017 – CBP detected nearly 24,000 non-compliant shipments. While most (17,413) of the non-compliances were crates or pallets that lacked the required mark showing treatment in accordance with ISPM#15, in 6,388 cases the wood packaging actually harbored a pest in a regulated taxonomic group. This works out to about 800 infested shipments detected each year.
By comparing Dr. Haack’s estimate with the CBP data, I estimate that Customs is detecting and halting the importation of four to eight percent of the shipments that actually contain pest-infested wood. Since CBP inspects only about two percent of incoming shipments, this detection rate demonstrates the value of CBP’s program to target likely violators – and deserves praise. But it is obviously too low a “catch” rate to provide an adequate level of protection for our forests.
Indeed, using the older, lower estimates of both numbers of shipping containers and the proportion that contain wood packaging, Leung et al. 2014 concluded that continuing to implement ISPM#15 at the efficacy level described by Haack et al. would result in a tripling of the number of non-native wood-boring insects introduced into the U.S. by 2050.
CBP inspector views Cerambycid larvae found in wood packaging that bears ISPM#15 stamp
Closer examination of the data raises more troubling questions. On average, 97% of the 6,388 shipments containing infested wood pieces detected by CBP were found in wood that bore the ISPM#15 stamp indicating that it had been treated. The proportion of infested shipments bearing the stamp has not changed over the past eight years. This is alarming and we need to understand the reason. Does this finding indicate widespread fraud? I understand that most inspectors believe this is the cause. Other possible explanations are accidental misapplication of the treatments or the treatments simply not working as expected. APHIS researchers have found that larvae from wood subjected to methyl bromide fumigation were more likely to survive to adulthood than those intercepted in wood that had been heat treated (Nadel et al. 2016). Does this indicate that methyl bromide fumigation is less effective? What effort is APHIS making to determine which of these explanations is correct?
Certain countries have a long-standing record of non-compliance with ISPM#15. APHIS’ database of pest interceptions on wood packaging over the period Fiscal Year 2011 to FY 2016 contains 2,547 records of insect detections from dozens of countries. The countries of origin with the highest numbers of shipments detected to have pests present were Mexico, China, Italy, and Costa Rica. These numbers reflect in part the huge volumes of goods imported from both Mexico and China. But China and Italy stand out for their poor performance. (The U.S. does not regulate – or inspect! – wood packaging from Canada; see blog here.)
Meissner et al. say that as of a decade ago, Chinese shipments were only half as likely to be enclosed in wood packaging as are shipments from other exporters. Yet shipments from China still rank second in the number of non-compliant shipments; they make up 11% of all interceptions. In part, the data reflect inspection priorities: due to the great damage caused by Asian insects to North American trees and the past record of poor compliance, CBP targets shipments from China for more intense scrutiny. Still, the high number of detections reflects continuing non-compliance by Chinese exporters. And remember – the U.S. and Canada began requiring treatment of wood packaging from China at the end of 1998 – nearly 20 years ago! [Feb 17 blog]
We don’t import a lot of goods from Italy – but Italian shipments of decorative stone and tile have always been plagued by high levels of pests in accompanying wood packaging. Indeed, more pests have been found in wood supporting tiles and stone than any other type of commodity in 24 of the 25 years preceding 2014 (Haack et al. 2014).
What is APHIS doing to pressure these countries to improve their compliance? As I blogged in October, link the Bureau of Customs and Border Protection began imposing a financial penalty on first-time violators in November 2017. Since interception data do not provide an adequate measure of the pest approach rate (see Haack et al 2014 for an explanation), APHIS should commission an analysis of Agriculture Quarantine Inspection Monitoring data to determine the pest approach rate before and after the CBP action in order to determine whether the more aggressive enforcement has led to reductions in non-compliant shipments at the border.
What Can Be Done to Slow or Eliminate this Pathway?
I reiterate my call for holding foreign suppliers responsible for complying with ISPM#15. One approach is to penalize violators. Now that the Bureau of Customs and Border Protection has toughened its enforcement, the U.S. Department of Agriculture should drop its decade-old policy of allowing importers to accumulate five (detected) violations in a calendar year before applying the civil penalties authorized by the Plant Protection Act.
Another step APHIS should take would be to prohibit use of packaging made from solid wood (boards, 4 x 4s, etc.) by foreign suppliers which have a record of repeated violations over the 12 years that ISPM#15 has been in effect – or the 19 + years for exporters from Hong Kong & mainland China. Officials should allow continued imports from those same suppliers as long as they are contained in other types of packaging materials, including plastic, metals, fiberboards …
SOURCES
Aukema, J.E., D.G. McCullough, B. Von Holle, A.M. Liebhold, K. Britton, & S.J. Frankel. 2010. Historical Accumulation of Nonindigenous Forest Pests in the Continental United States. Bioscience. December 2010 / Vol. 60 No. 11
Haack, R. A., K. O. Britton, E. G. Brockerhoff, J. F. Cavey, L. J. Garrett, M. Kimberley, F. Lowenstein, A. Nuding, L. J. Olson, J. Turner, and K. N. Vasilaky. 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:e96611.
Hulme, P.E. 2009. Trade, transport and trouble: Managing invasive species pathways in an era of globalization. Journal of Applied Ecology 46:10-18
Jung, T. et al. 2015 “Widespread Phytophthora infestations in European nurseries put forest, semi-natural and horticultural ecosystems at high risk of Phytophthora disease” Forest Pathology. November 2015; available from Resource Gate
Klapwijk, M.J., A.J. M. Hopkins, L. Eriksson, M. Pettersson, M. Schroeder, A. Lindelo¨w, J. Ro¨nnberg, E.C.H. Keskitalo, M. Kenis. 2016. Reducing the risk of invasive forest pests and pathogens: Combining legislation, targeted management and public awareness. Ambio 2016, 45(Suppl. 2):S223–S234 DOI 10.1007/s13280-015-0748-3
Koch, F.H., D. Yemshanov, M. Colunga-Garcia, R.D. Magarey, W.D. Smith. 2011. Potential establishment of alien-invasive forest insect species in the United States: where and how many? Biol Invasions (2011) 13:969–985
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.org
Levinson, M. The Box: How the Shipping Container Made the World Smaller and the World Economy Bigger Princeton University Press 2008
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. www.frontiersinecology.org
Meissner, H., A. Lemay, C. Bertone, K. Schwartzburg, L. Ferguson, L. Newton. 2009. Evaluation of Pathways for Exotic Plant Pest Movement into and within the Greater Caribbean Region. Caribbean Invasive Species Working Group (CISWG) and USDA APHIS Plant Epidemiology and Risk Analysis Laboratory
Meurisse, N. D. Rassaati, B.P. Hurley, E.G. Brockerhoff, R.A. Haack. 2018. Common Pathways by which NIS forest insects move internationally and domestically. Journal of Pest Science. https://doi.org/10.1007/s10340-018-0990-0
Nadel, H., S. Myers, J. Molongoski, Y. Wu, S. Linafelter, A. Ray, S. Krishnankutty, A. 2016. Identificantion of Port Interceptions in Wood Packaging Material Cumulative Progress Report, April 2012 – August 2016
Yemshanov, D., F.H. Koch, M. Ducey, K. Koehler. 2012. Trade-associated pathways of alien forest insect entries in Canada. Biol Invasions (2012) 14:797–812
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.
CBP inspecting wood packaging; CBP photo
shipment of decorative stone with wood packaging