Biotic resistance limits the invasiveness of the western flower thrips, Frankliniella occidentalis （Thysanoptera： Thripidae）, in Florida

The spread of the western flower thrips, Frankliniella occidentalis （Pergande）, has resulted in the world-wide destabilization of established integrated pest management programs for many crops. It is hypothesized that frequent exposure to insecticides in intensive agriculture selected for resistant populations, which allowed invasive populations in the eastern USA to overcome biotic resistance from the native community of species. Research conducted in Florida to understand the role of biotic factors in limiting the abundance of the western flower thrips is reviewed. Orius spp. （Hemiptera： Anthocoridae） are effective predators that suppress populations of thrips on crop and non-crop hosts in southern and northern Florida. Orius are more effective predators of the western flower thrips than the native flower thrips, E tritici （Fitch） and E bispinosa （Morgan）. The native species are competitors of the western flower thrips. Excessive fertilization and the use of broad-spectrum insecticides in crop fields further enhances populations of the western flower thrips. Interactions with native species clearly limit the abundance of western flower thrips in Florida, but populations are abundant in fertilized crop fields where application of insecticides excludes predators and competitor species.