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Plant-Insect Ecosystems

Poster: P-IE, Resistance

D3499: Corn earworm populations in the southeastern United States are still relatively susceptible to common insecticides in laboratory bioassays

Tuesday, November 12, 2024
9:00 AM – 5:00 PM MST
Location: Phoenix Convention Center, Exhibit Hall 6, PCC
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Abstract: The corn earworm, Helicoverpa zea, is one of the widely distributed lepidopteran pests that feed on a variety of host plants in North America. Over the last quarter century, this pest on corn and cotton in the U. S. has been primarily controlled by planting transgenic Bt crop varieties. As a result, H. zea has developed high levels of resistance to the Cry Bt proteins expressed in both crops. In recent years, field crops, especially cotton, in the southern region have encountered increased H. zea infestations. In this study, laboratory bioassays were performed to determine the susceptibility of six H. zea populations collected from corn fields in five U.S. southeastern states to eight common insecticides: Diamond, Intrepid, Vantacor, Steward, Spinosad, Warrior II, Orthene, and Dimilin. Compared to the responses of a known-susceptible laboratory strain, all six field populations were still  susceptible to Orthene, Vantacor, Spinosad, and Dimilin with a susceptibility ratio ranging from 0.5- to 4.6-fold, while low levels of resistance (≤ 13.6-fold)  to Warrior II, Steward, Dimond, and Intrepid were observed in a few populations. The results of this study suggest that H. zea populations in the southeastern U. S. appeared still relatively susceptible to the tested insecticides.  


Key words: H. zea, insecticides, dose-response bioassay, susceptibility