Influence of agronomic hosts on the susceptibility of Helicoverpa zea (Boddie) (Lepidoptera:Noctuidae) to genetically engineered and non-engineered cottons

Field and laboratory studies evaluated the influence of selected crop hosts on Helicoverpa zea (Boddie) population dynamics in relation to genetically engineered Bt (Bollgard) and non-Bt cottons. Host specific H. zea colonies were initiated with a colony originally collected from sweet corn. The colony was allowed to complete one generation on meridic diet then split into cohorts and allowed to complete one generation on field corn, grain sorghum, soybean, cotton, or meridic diet in individual 29.5 ml plastic cups. During the first part of the study, larval developmental times, pupal weights, and survival were measured. H. zea survival was higher on meridic diet and grain sorghum than on soybean and cotton. Development of H. zea larvae was faster on field corn than all other larval diets. Also, H. zea required a longer period of time to complete development on cotton than on the other hosts. Pupal weights were higher on meridic diet than the plant hosts. Pupal weights of H. zea that completed larval stadia on cotton were lower than on the other larval diets. Neonates (F-1) from each of the host specific colonies (200 per colony) were exposed to Bt and non-Bt cottons. Mortality of second generation H. zea on non-Bt and Bt cottons was measured at 96 h. H. Zea larvae from the cotton colony had higher mortality on non-Bt cotton than the other host specific colonies except the grain sorghum colony. On Bt cotton, larvae from the corn colony had a higher level of mortality than larvae from the soybean and grain sorghum colonies. These data provide valuable information for evaluating the contribution of cultivated hosts as additional, alternative refugia in Bt cotton resistance management plans.