The silverleaf whitefly (SLW), Bemisia tabaci B-biotype, was first discovered in Australia in 1994 (Gunning et al 1995). SLW is a major pest of cotton and other crops in many overseas countries and poses a considerable threat to cotton in Australia. SLW is the second biotype of B. tabaci be found in Australia. A closely related indigenous biotype (IBW) was first recorded from Australia in 1959 (Carver and Reid 1996). Molecular phylogenetic studies (De Barro unpublished data) indicate that IBW is unique to Australia and some near Pacific Island countries. IBW is an efficient vector of tomato geminiviruses that were extremely damaging to the Northern Territory tomato industry, but unlike SLW does not cause feeding related damage. Since its detection, SLW has spread widely in New South Wales and Queensland. However, its spread into the cotton growing regions of both states has been slower than in the areas dominated by vegetable horticulture. Given the threat posed by SLW to cotton in Queensland a monitoring system using surveys was established and has been run over the past two years