The parasitoid Aphidius colemani developed normally (approximately 90% adult emergence) when its cotton aphid (Aphis gossypii) host was treated with Verticillum lecanii conidia 5 or 7 days after parasitization. Fungus exposure 1 day before or up to 3 days after parasitization, however, reduced A. colemani emergence from 0 to 10%. Also, numbers of spores and mycelial fragments in aphid homogenates were much higher in aphids exposed to the fungus up to 3 days after parasitization than in aphids treated after 5 or 7 days. Our results suggest that the parasitoid and fungus may be used together for aphid biocontrol as long as fungus applications are timed to allow late-instar development of the parasitoid. [copyright] 2005 Elsevier Inc. All rights reserved. Aphidius colemani (Aphidiidae) Life cycle and development; Development; Parasites diseases and disorders; Diseases and disorders; Microbial diseases Aphidius colemani; Larval development; Late-instar development; Fungal diseases; Fungal impact on late-instar development; biocontrol implications; greenhouse study; Verticillium lecanii none