Asian Gypsy Moth

Lymantria dispar asiatica and Lymantria dispar japonica

Last updated by: 
Faith Campbell

Two subspecies of gypsy moth  - Lymantria dispar asiatica Vnukovskij and Lymantria dispar japonica Motschulsky – are present in Asia.  Lymantria dispar asiatica is found throughout temperate Asia, including the Russian Federation, the Republic of Korea, Mongolia and the Democratic Peoples Republic of China. Lymantria dispar japonica is found in Japan.  (NAPPO RSPM #33)

The Asian gypsy moths present an even greater threat than the European gypsy moth (L. dispar L)  because they feed upon an even greater variety of plants - more than 600 species of plants, including alder, ash, beech, birch, chestnut, elm, hornbeam, linden, maple, oak, poplar, sumac, trembling aspen, walnut, willow, fruit trees, and certain conifers, including some cedars, Douglas fir, hemlock, juniper, larch, pine, redwood, spruce and some true firs. (NAPPO RSPM#33).  In addition, unlike the European strain, the female Asian gypsy moths have the ability to fly up to 40 kilometers (NAPPO RSPM#33); this attribute would greatly accelerate dispersal and colonization if the moths were to escape.

The insect is attracted to lighting at ports, where the females can lay their eggs on ships at anchor or the containers on them.  During periods of heavy infestations, regulatory authorities in Russia have reported hundreds of egg masses on a single vessel. (NAPPO RSPM#33)

During the early 1990s, the Asian gypsy moth reached North America on both western and eastern seaboards several times as egg masses on ships (USDA APHIS & Forest Service, 2000). Each time, emergency control programs succeeded in eradicating the moth.  Beginning in 1992, the CFIA and USDA have required regulatory inspection and other measures for ships that have visited infested ports in the Russian Federation.

Beginning in 1998, detections have been made on ships and cargo aboard ships which had visited Japan during the female gypsy moth flight period.  Similar detections were made on ship that had called on ports in the People’s Republic of China and the Republic of Korea since the mid-2000s.  The sense of urgency rose in 2008, when Asian gypsy moth egg masses were detected on 23 ships coming from those countries to North America (18 were detected in U.S. ports, 5 in Canadian ports).  Most of these ships were from Japan.  Much lower numbers had been detected on ships in earlier years – although AGM were found in traps in several U.S. mainland locations during this period.  The 2008 spike might reflect both a “high” in moth population cycles and a 500% increase in US Customs and Border Protection ship inspection efforts beginning in 2007.   In the first 9 months of 2009, approximately 10 ships with egg masses had been detected in Canada, 6 in the U.S.  (Michael Simon, USDA APHIS, pers. comm. Sept 2009)

In response to the rising numbers of detection, Canada, Mexico and the United States – working together through the North American Plant Protection Organization (NAPPO) –developed a regional standard to protect all of North America.  After several rounds of negotiations with officials from China, Japan, and Korea, NAPPO adopted the regional standard (RSPM #33) in August 2009.  RSPM#33 provides several options for how the Asian countries could prevent transport of Asian gypsy moths to North America aboard ship superstructures or cargo containers leaving their ports:

  • Inspection and removal of egg masses by the exporting country;
  • Systems Approaches – implementation of a systems approach utilizing surveillance and monitoring of insect populations combined with exclusionary tactics (e.g. tree removal in areas near ports, reduction or altering of port lighting, the use of areas of low pest prevalence, etc.)
  • Designation of areas of the country as free of gypsy moths – verified by monitoring, etc.
  • Other measures acceptable to the NAPPO parties

The three NAPPO countries (Mexico, USA, Canada) in turn may require phytosanitary certificate for ships and inspect ships before they enter a North American port.  They may also refuse entry of any ship lacking a phytosanitary certificate.  If AGM are detected, the ship is required to leave waters of the entire NAPPO region until it has been cleaned.  If there are repeated incidents of non-compliance, the NAPPO countries will review the exporting country’s management program.

Full implementation of the standard will be phased in over a few years.



North American Plant Protection Organization (NAPPO) Regional Standards for Phytosanitary Measures (RSPM) #33. 2009. Guidelines for Regulating the Movement of Ships and Cargoes aboard those Ships from Areas Infested with the Asian Gypsy Moth

United States Department of Agriculture, Animal and Plant Health Inspection Service and Forest Service 2000. Pest Risk Assessment for Importation of Solid Wood Packing Materials into the United States. USDA APHIS and Forest Service. August 2000.

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