The effects of diet on the detection of resistance to Cry1Ac toxin in Australian Helicoverpa armigera Hubner (Lepidoptera: Noctuidae)

The effects of raw or heat-denatured soybean flour in an artificial diet on the detection of Cry1Ac resistance in Helicoverpa armigera were examined Resistant neonate larvae reared on denatured soybean flour diet showed resistance factors of 7980 and 16,901 at the LC50 and LC99 9 levels, respectively By comparison, resistance could not be detected in neonate larvae reared on raw flour diet. Third instar larvae reared on denatured flour diet showed resistance factors of 322 and 21.190 at the LC50 and LC99 9 levels Resistance was not detected in third instar larvae reared on raw flour diet There was 68% survival of resistant neonate larvae on Bollgard II cotton leaf feeding assays, compared to 100% mortality in a susceptible strain We conclude that detection of CRY1Ac resistance in H armigera from Australia can be masked, if an artificial diet gives chronic exposure to potent, protease inhibitors present in raw soy flour (C) 2009 Elsevier Inc. All rights reserved