Development of genetic markers to study dispersal of Diamondback moth, Plutella xylostella (L.) in Australia

The origin and insecticide resistance status of Diamondback moth (Plutella xylostella) populations infesting canola, vegetables, forage brassicas and weeds has fundamental implications for management of the pest in Australia. Diamondback moth is considered a migratory species in the Northern Hemisphere, but although there is evidence that Diamondback moth moves en-masse throughout Australia in some seasons, its longrange movement patterns in this country have not been ascertained. Severe outbreaks of Diamondback moth in canola in Western Australia in 2001 and in NSW in 2002 have emphasised the need for greater understanding of dispersal of Australian populations of Diamondback moth. Microsatellite markers have the potential to provide an appropriate level of resolution to study population structure and movement in Diamondback moth and have been isolated by screening a partial genomic library and an Expressed Sequence Tag (EST) library for repeat sequences in the DNA. The markers are being used to investigate moth dispersal and genetic structure of populations from a range of host plants and locations. Combined with studies of insecticide resistance in Diamondback moth, information about mixing or isolation of Australian moth populations will aid in tracking the spread or dilution of insecticide resistance genes. The information will be used to optimise insecticide resistance management and other management strategies for Diamondback moth in Australia.