Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Master of Science in Entomology (MS)

Degree Level

Graduate

Department

Entomology and Plant Pathology

Advisor/Mentor

Thrash, Benjamin C.

Committee Member

Bateman, Nicholas R.

Second Committee Member

Nalley, Lawton L.

Third Committee Member

Lorenz, Gustav M. III

Keywords

Bollworm Helicoverpa zea; Bt Cotton; Cotton economics; Insect pest management; Row crop; Transgenic cotton

Abstract

Helicoverpa zea is the second most damaging insect pest of cotton in Arkansas. It is becoming more difficult to control in the United States due to recently documented resistant to dual gene cultivars. The objective of this thesis was to develop a better understanding of the efficacy of several Bt cotton technologies and foliar insecticides used to manage H. zea. Experiments examined damage in current commercial non-Bt, dual gene, and three gene cotton cultivars. Other experiments evaluated if H. zea could detect concentrations of chlorantraniliprole and residual of chlorantraniliprole in cotton for an extended period after application. These studies suggest that chlorantraniliprole has the potential to provide control of H. zea up to 28 days after treatment, based on lab analysis of residual concentrations in multiple fruiting structures. Results from both studies suggest that H. zea was not able to detect chlorantraniliprole at the tested concentrations. Dual gene appears to provide adequate control of H. zea under low pressure. However, dual gene alone may not provide satisfactory control of H. zea when pressure is moderate or greater and supplemental foliar insecticide applications may be required. Three gene cultivars appeared to provide sufficient control of H. zea but should still be monitored to prevent yield loss. Grower’s planting dual gene cul¬tivars should budget at least one application of a diamide insecticide to prevent yield loss. Information was col¬lected from the Arkansas Field Crops Enterprise Budget to compare dual gene and three gene production and input cost. Compared to dual gene cotton, three gene cotton reduces insecticide use, lessens the amount of diesel used, decreases time spent in the field, and has a higher seed cost per acre. A simulated scenario was conducted to determine the profit and breakeven percentage for cotton growers. The simulated profit and breakeven percentage was calculated using the average yield, average market price of cotton, and the average expenses per acre. This simulation showed what growers can expect to profit or if they will breakeven based on the cotton cultivar or if a foliar insecticide application is used. Results from these experiments will be important for refining management recommendations for H. zea in Bt cotton.

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