Asian Gypsy Moth

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)

Beginning in the early 1990s, the Asian gypsy moth has 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 Canadian Food Inspection Service and USDA Animal and Plant Health Inspection Service required that ships that had visited infested ports in the Russian Federation undergo inspection and other measures to ensure that no Asian gypsy moth egg masses are present.

Detections of AGM egg masses on ships and cargo aboard ships which had visited Japan, People’ Republic of China, and Republic of Korea began occurring in 1998.  Numbers varied considerably, but reached a high of 23 ships in 2008  (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 took effect in 2012.

However, detections of infested ships continue – even increase.  In calendar year 2011, 21 ships were detected with Asian gypsy moth egg masses.  In 2012, the number doubled, to 44.  Another 42 infested ships were detected in 2013.  In 2014, Customs and Border Protection detected infestations on 50 ships (Harriger presentation).

While most of the infested ships are attempting to dock at West Coast ports, some are approaching other regions.   In 2013, Asian gypsy moth eggs were detected on a ship that had travelled from Japan to Europe, then on to the U.S. east coast.  Egg masses were discovered when the ship arrived at Baltimore; additional egg masses were detected during the ship’s transit to Brunswick, Georgia; and again when it reached that port (CBP Press Release September 2013).

One of the most recent detections in the United States of Asian gypsy moth was in Oklahoma, again in 2013; authorities believe that insect arrived in military equipment (Berger).

All known detections of Asian gypsy moth have been monitored and eradicated.  Nevertheless, the risk of introduction of this highly damaging pest appears to significant.

USFS scientists and managers developed a conservation priority-setting framework for forest tree species at risk from pest & pathogens and other threats. The Project CAPTURE (Conservation Assessment and Prioritization of Forest Trees Under Risk of Extirpation) uses FIA data and expert opinion to group tree species under threat by non-native pests into vulnerability classes and specify appropriate management and conservation strategies. The scientists prioritized 419 tree species native to the North American continent. The analysis identified 15 taxonomic groups requiring the most immediate conservation intervention because of the tree species’ exposure to an extrinsic threat, their sensitivity to the threat, and their ability to adapt to it. Each of these 15 most vulnerable species, and several additional species, should be the focus of both a comprehensive gene conservation program and a genetic resistance screening and development effort.  Asian Gypsy Moth is not known to be a threat to any of these 15 most vulnerable species. 


Additional Web Resources:



Berger, P. United States Department of Agriculture. Animal and Plant Health Inspection Service.  Presentation to the Continental Dialogue on Non-Native Forest Insects and Diseases, November, 2014.

Department of Homeland Security, Bureau of Customs and Border Protection. 2013.  Press Release “CBP and Merchant Ship Crew Intercept 27 Destructive Asian Gypsy Moth Egg Masses on Car Carrier Ship.” (Monday, September 30, 2013)

Harriger, K.C. Deputy Executive Director, Agriculture Operational Oversight, Department of Homeland Security, Bureau of Customs and Border Protection. Presentation to the Continental Dialogue on Non-Native Forest Insects and Diseases, November, 2014.

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

Potter, K.M., Escanferla, M.E., Jetton, R.M., Man, G., Crane, B.S., Prioritizing the conservation needs of US tree spp: Evaluating vulnerability to forest insect and disease threats, Global Ecology and Conservation (2019), doi:

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.