The commercialization of cotton and corn, genetically engineered to produce a caterpillar-specific insecticidal protein (Bt toxins) has focused renewed attention on the issue of southward migration because it could have a major effect on the rate at which H. zea may evolve resistance to this Bt toxin. We applied a stable carbon isotope technique to test the hypothesis that H. zea migrates North in early summer, feeds on corn, then migrates back South to feed on cotton. We analyzed the naturally occurring isotope, 13C, incorporated in wing keratin to indicate the host plant photosynthetic pathway (corn=C4, cotton=C3) as a supportive indicator of moth natal origin. Our analyses of H. zea at College Station, Texas, from late summer to early fall demonstrate that 40-100% of the moths developed on C4 host plants and are present as adults in a cotton growing area where there were no known C4 hosts suitable for development. Our preliminary investigation has shown significant morphometric differences in moths from C3 and C4 hosts. These differences have led us to our working hypothesis that moths migrating to the southern states will be larger than those that developed on cotton late in the summer.
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Back to The 2002 ESA Annual Meeting and Exhibition