Asian Gypsy Moth Update 2020

Introduction

The Asian Gypsy Moth (AGM, including Lymantria dispar asiatica, Lymantria dispar japonica, Lymantria albescens, Lymantria umbrosa, Lymantria postalba) is a highly destructive forest pest that feeds on both deciduous and coniferous trees.

The voracious appetite of AGM larvae (caterpillars) coupled with the ability of the female moth to travel significant distances (as much as 20 nautical miles) can cause widespread defoliation leaving trees weakened and susceptible to disease and other pests.

AGM is found primarily in the Far East with a high risk of AGM egg infestation of vessels calling at ports in Korea, Northern China (north of Shanghai; ports north of latitude 31˚15’N), and in particular the Russian Far East and Japan during the flight season of the female moth.

Due to their destructive nature, particularly in countries where the pest is not indigenous, the following countries have specific procedures in place to prevent AGM from entering their fragile ecosystem:

• Australia
• Canada
• Chile
• New Zealand
• United States

AGM Flight Season

The main concern to countries attempting to prevent the introduction of the AGM are vessels that have called at ports in the AGM High Risk Area during the previous years “flight season”.

The specific timing of the “flight season” differs from country to country. Canada and the United States base their AGM policy on the following areas and flight seasons:

Australia, Chile and New Zealand have their own designated flight season areas and dates, which differ slightly from the above.

Asian Gypsy Moth Characteristics

Male AGMs are greyish brown with a wingspan of 30 to 40 mm. Females are whitish / pale yellow in colour with prominent black marks on the wings and are larger than the male with a wingspan of 40 to 70 mm.

^{Image courtesy of U.S. CBP} 

It is unlikely that live AGMs will be encountered by vessels in transit. It is more likely that egg masses will be found.

Female AGMs are active flyers and are attracted to bright lights, therefore AGM eggs may be found in the vicinity of exterior lights and floodlights on vessels. If powerful shore lights are directed towards the vessel, AGM eggs may be found all over the ship and its cargo. Where safe and practicable to do so, external lights on vessels should be switched off.

AGM eggs are velvety in texture and range in colour from light tan to dark brown. A typical egg mass will contain between 500 and 1000 eggs and measure approximately 20 mm by 40 mm. The eggs are particularly hardy and resistant to changes of temperature and moisture. They are normally deposited in sheltered locations, for example, under canvas covers, around light fixtures and underneath framing arrangements such as hatch coamings and the underside of bridge wings. Egg masses have also been found on mooring lines, on the outside of shipping containers and on vehicles, for example in wheel arches.

The larvae normally hatch in early spring, therefore this is considered the high risk period in countries that wish to stop this species becoming established, hence vessels that call in the Far East during the flight season, and then subsequently arrive in port during the hatching period, are of particular concern.

The peak period for egg hatching is in the morning; the dispersing larvae move towards vertical structures, climb rapidly to a high point and are then widely dispersed on silken strands by the wind until they find suitable host trees to feed on, a process known as “Ballooning”.