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Jon Bell The word “hitchhiker” has many connotations but in the Plant Quarantine regulatory world, a hitchhiker is defined as a contaminating pest or “a pest that is carried by a commodity and, in the case of plants and plant products, does not infest those plants or plant products” (1). Countless species have been inadvertently moved around the globe in some way attached to or involved with nontraditional pathways and have circumvented quarantine measures. Some of these exotic species have established in a new ecosystem and become pests and cause severe economic and ecological damage. A pest, as defined by the Plant Protection Act of the Canadian Food Inspection Agency (CFIA), is “anything that is injurious or potentially injurious, whether directly or indirectly, to plants or to products or by-products of plants, and includes any plant prescribed as a pest”(2). Most examples of hitchhikers have occurred in the agricultural sector where items such as soil, act as a medium to move insects and pathogens. Legislation exists in most countries to prevent the movement of soil containing both invertebrates and plant and animal disease organisms. In the forest industry, used harvesting equipment can be a vector for soilborne diseases as well as a traditional pathway of insects and diseases in wood debris. This pathway of used forestry equipment is easily defined and custom agencies can readily screen imported commodities by use of an internationally recognized 10-digit harmonization code system (HS-Code) (3). Identified risk material can then be diverted for inspection and mitigation measures, if necessary (Fig. 1). The undefined or undetermined pathways cause the most concern to plant quarantine regulators. A recent example of a pathway for forest hitchhikers is the movement of Lymantrids from the Commonwealth of Independent States (CIS) to Europe and North America.
The history of Asian gypsy moth (AGM), Lymantria dispar (Fig. 2), in North America goes back to 1911 when viable egg masses were intercepted on Thuja trees imported into British Columbia from Japan. A second incident occurred in 1982 when egg masses were found on a Soviet vessel in Vancouver. The eggs were incubated, larvae reared on wheat debris, and confirmed as AGM. This was the first instance of gypsy moths (GM) associated with grain vessels, but it failed to trigger any concern because it was so different from the accepted concept of where and when GM would occur. Asian GM differs from North American (but originally French) GM in that the female is flighted and has a wider host range. In the fall of 1990, a series of dead AGM females was found in the holds of Soviet grain vessels. By February of 1991, the seriousness of AGM was understood and a meeting was held with a U.S. Forest Service entomologist and Agriculture Canada staff to develop a strategy to prevent the introduction of AGM into the Port of Vancouver, BC. Due to environmental restrictions on using a chemical insecticide over an aquatic environment, the only product deemed suitable that would prevent AGM larvae from blowing (ballooning) from a vessel was an aerosol formulation of Tanglefoot© (insect trap coating). Due to the numbers of egg masses and drifting and crawling larvae (Fig. 3), the Tanglefoot© treatment proved inadequate and the only option remaining was the removal of the vessels from area.
The result that spring of 1991, was that nine Soviet vessels were banned from Canadian waters until they had removed all egg masses and larvae. The cleaning, which took place at sea, was inadequate as vessels were cleaned and reinspected several times over but removing all traces of AGM proved impossible. In one instance, half a 45-gallon drum of egg masses and scale was collected from a vessel that was sent back to sea for recleaning. Lloyd’s of London provided a searchable database (Seadata©) to enable staff to screen out vessels that had not been in Vladivostok or Nahodka in the Russian Far East, the center of the AGM outbreak. Using the computer-sorted data permitted staff to focus on high risk vessels only and not waste limited manpower. Rather than face the embarrassing situation of a vessel being found contaminated with AGM and banned from Canadian waters, the Soviet Navy cancelled their goodwill visit of 1991. L. mothura and L. monacha exist in the Russian Far East along with L. dispar and present a risk of moving on vessels and containers. A 1992 record of an interception of L. mothura from a Soviet vessel confirms this pathway. Disparlure pheromone-baited delta traps were placed around the harbor of Vancouver to assess whether AGM had been prevented from reaching local trees. GM males were trapped close to a loading facility where an infested ship had berthed that spring and adjacent to English Bay, the anchorage immediate to the city center of Vancouver. Researchers at Cornell University had been working with the then new technique of polymerase chain reaction (PCR) to differentiate biotypes of GM, and that fall they were able to confirm that adult male moths trapped in Vancouver were AGMs. Rather than risk establishment of AGM or face the prospect of being quarantined, Canada chose to eradicate AGM in 1992. Bacillus thuringiensis Kurstski was sprayed over 18,000 ha in the Greater Vancouver Regional District at a cost of 6 million dollars (Fig. 4). That same spring, similar eradication projects were undertaken for AGM in Seattle, WA and Portland, OR in the United States. The Vancouver project met with major objections from environmental and citizen action groups, which 8 years later still protest the government’s actions to eradicate GM at small localized sites within the Province of British Columbia.
The population of AGM still exists in the CIS and measures remain in place to prevent the movement of egg masses on vessels that have been in the Russian Far East during the summer high risk period (Fig. 5). The risk period has been quantified by the use of pheromone traps placed in and around CIS port areas and monitored to obtain first and last male flight dates. Mitigating measures carried out in the port areas and on vessels are light level modification, avoidance of peak flights, treatments, and quarantine agency inspection and certification. The certification by CIS inspectors is followed by vessel inspection at sea or at the port of loading by the local quarantine agency. The preloading inspection is also time limited and is carried out in the high risk period of egg hatching and larval ballooning, such as spring and summer in North America. The full AGM policy is available on the CFIA website (4). AGM from central Siberia was moved into Europe sometime after 1945, and the resulting population created problems for containers being moved to North America from Western Europe. Military supplies stored in containers in Germany in 1993 became contaminated with pupating AGM and were responsible for moving adult life stage AGM to the U.S. east coast. Once the pathway was discovered, military material and containers coming from Europe back to NA required GM inspection prior to shipping. Again, a large and costly eradication program was required to eliminate this pest incursion. Prior to the 1993 event, in the late 1980s, a container from Europe was intercepted in California with hundreds of GM egg masses on the undersurface of the container. Unfortunately, no samples were retained and the PCR test was not available to determine if it was AGM or GM. Other objects that are stored out of doors, often under high light levels, are subject to infestation with egg masses of Lymantrids. New automobiles from Asia were found in New Zealand with viable egg masses. The 1992 population of AGM has been eradicated, but Canada remains vigilant, constantly trapping and inspecting ships, looking for AGM egg masses that could be anywhere on the exterior of large modern ships that have visited the high risk area in Asia. Random vessel inspection has produced other AGM egg mass finds on vessels not having visited the Russian Far East, which causes the question to be asked: what other Asian area or port is the source of these interceptions? Has AGM or a similar pest been successfully introduced into North America or a new area of the globe? Due to the actions of Canada and the United States in dramatically limiting the entry of AGM, the risk for this particular insect entering has been substantially reduced, however continued vigilance will be required for many other pests and diseases. Global trade will continue to increase and the challenges for quarantine agencies will be even greater in the future as new markets and products enter world commerce. The odds are quite high that many other forest insects and diseases have been moved and are on the threshold of either failure or survival in their new site. At this time we have not detected their presence, either due to lack of detection tools or because the pest has not reached an economic or visible threshold. References: 1) Plant Protection Act of the Canadian Food Inspection Agency. 2) International Standards for Phytosanitary Measures ISPM 5 Glossary of Phytosanitary Terms [CEPM, 1996; revised CEPM, 1999] http://www.fao.org/ag/agp/agpp/pq/ 3) International Convention on the Harmonized Commodity Description and Coding System. June 1983 http://www.wcoomd.org/frmpublic.htm 4) CFIA D-95-03 Asian Gypsy Moth (Lymantria
dispar L.) - Plant Protection Policy For Ships. http://www.cfia-acia.agr.ca/english/plaveg/protect/dir/
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