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Oral Presentation
Oral Presentation
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Poster Display
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Student Competition
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Ticketed Event

Student Poster Display Competition

Plant-Insect Ecosystems

Student Competition

Student

Grad Poster Competition: P-IE, IPM 2

Susceptibility of Helicoverpa zea to eight common chemical insecticides in the southeastern United States

Monday, November 10, 2025
9:00 AM - 5:00 PM Pacific
Location: Exhibit Hall A-A1, OCC
Poster Display Student Competition
The widespread resistance to Cry Bt crops in the bollworm/corn earworm, Helicoverpa zea, coupled with the increased infestations of the insect in the southern region of the U.S., especially in cotton fields, has forced crop growers to use more chemical insecticides to control the pest. In this study, diet-overlay and diet-incorporated bioassays were performed to determine the susceptibility of 17 H. zea populations collected from corn and sorghum field in six southeastern states of the U.S. in 2023 and 2024 to eight common insecticidal chemistries: acephate, λ-cyhalothrin, chlorantraniliprole, diflubenzuron, indoxacarb, methoxyfenozide, novaluron, and spinosad. Relative to a laboratory reference insect strain, the field-collected populations were still susceptible to acephate, chlorantraniliprole, and spinosad. Most populations had shown low to moderate levels of resistance to diflubenzuron (1.9- to 7.8-fold), indoxacarb (1.6- to 13.0- fold), and methoxyfenozide (1.4- to 30.9-fold), while some populations had already evolved high levels of resistance to λ-cyhalothrin (up to >51.8) and novaluron (up to 142.0-fold). For each of the eight insecticides, there is no significant differences in the mean LC50s between the populations collected in 2023 and 2024 or between the populations collected from Bt plants and non-Bt plants. There were also no correlations in the LC50 values between each two of the insecticides that the insect had already shown resistance. The information generated from the study should be useful in guiding proper rotation and integration of different insecticides to prolong their efficacy to manage H. zea in the southern region of the U.S..