|Throne, James - Jim|
Submitted to: Journal of Applied Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/3/2005
Publication Date: 6/1/2005
Citation: Qureshi, J.A., Buschman, L.L., Throne, J.E., Ramaswamy, S.B. 2005. Adult dispersal of Ostrinia nubilalis Hubner (Lepidoptera: Crambidae) and its implications for resistance management in Bt-maize. Journal of Applied Entomology. 129(6):281-292. Interpretive Summary: The European corn borer is an important economic pest of corn in North America and Europe, and damage and control costs exceed one billion per year in North America alone. European corn borer is a primary target of transgenic Bt corn hybrids; however, there is concern that the European corn borer could develop resistance to the insecticidal protein expressed in Bt corn plants. Insecticide-resistance management strategies have been developed to try to slow resistance to the insecticidal protein, but, for these strategies to work, there needs to be enough dispersal of adults between transgenic and nontransgenic "refuge" crop fields to allow genetic mixing of the populations to suppress development of pest resistance to the transgenic crop. Dispersal of European corn borer adults was investigated in western Kansas where corn is grown under irrigation in a semi-arid climate to determine whether dispersal assumptions used in development of the resistance management strategy for European corn borer were appropriate. Dispersal of marked insects suggests that a minimum distance of 300 m between Bt corn and non-Bt corn "refuge" would be appropriate; however, dispersal of naturally occurring adults suggests that dispersal from neighborhood fields was more extensive than suggested by marked adults. This implies that the currently used resistance management strategy for European corn borer is appropriate for irrigated corn fields.
Technical Abstract: Dispersal of European corn borer, Ostrinia nubilalis Hübner, was determined by release and recapture of dye-marked adults and by capture of the feral adults in and around 50 ha center pivot irrigated Bacillus thuringiensis (Bt) maize fields. Pheromone and black light traps were used to catch the adults. There needs to be enough dispersal of adults between transgenic and nontransgenic "refuge" crop fields to allow genetic mixing of the populations to suppress development of pest resistance to the transgenic crop. In 1999, 15,094 marked males and 7,993 marked females were released, and in 2001, 13,942 marked males and 9,977 marked females were released. In 1999, maximum mean recapture beyond the release point was 1.95% and 1.67% for males and females, but in 2001, the recapture rate was 9.97% and 4.37% for males and females. Few males (3.8%) and females (2.07%) were recaptured in neighborhood maize fields. An exponential decay function explained recapture across the dispersal distance. More than 90% of marked adults were recaptured within 300 m of the release point. These observations suggest that a minimum distance of 300 m between Bt maize and non-Bt maize "refuge" would seem to be in order. However, large numbers of feral adults were captured throughout the study fields. Feral adult dispersal could be fitted to a linear model. This suggests that dispersal from neighborhood fields was more extensive than suggested by marked adults. This could mean that the resistance management strategy for O. nubilalis is fairly robust. Marked (20%) and feral (8%) virgin females were captured throughout the study fields. The implications of these findings to manage corn borers resistance against Bt-maize are discussed.