Global establishment threat from a major forest pest via international shipping: Lymantria dispar

The global shipping network is widely recognised as a pathway for vectoring invasive species. One species of particular concern is Lymantria dispar (gypsy moth). Two subspecies, L. d. asiatica and L. d. japonica (herein referred to as Asian Gypsy Moth - AGM) are of considerable concern as ships arriving to a number of countries have been found carrying AGM egg masses. However, ships carrying AGM eggs can only threaten a country at ports located in a climatically suitable region. We present a CLIMEX model of climate suitability and combine this with international shipping to estimate the global threat from AGM. We find that for the USA more than half of international ships (approximately 18,000 ships) arrive to climatically suitable ports. Other countries with a large number of ships arriving to ports with suitable climates include Canada and Brazil. This is the first global analysis of the invasion threat from AGM, and we recommend countries focus AGM-inspection programs towards ships arriving at ports found within climatically suitable regions.