Chemical Control and Bioeconomics of Smicronyx fulvus on Cultivated Sunflower in North Dakota123

Abstract
Endosulfan, fenitrothion, and phosmet at 1 and 2 kg AI/ha, and methidathion at 0.5 and 1 kg Al/ha were evaluated for efficacy in managing populations of a seed weevil, Smicronyx fulvus LeConte, on cultivated sunflower, Helianthus annuus L. Insecticidal control of S. fulvus was directed at adults. Two applications of insecticides, at the lowest rates tested, significantly reduced damage when compared to controls. S. fulvus larvae consumed 31% by weight of a seed in hybrid 894, and larval feeding subsequently reduced oil content by 25% in damaged vs. non damaged seed. Calculation of an economic injury level for 22 S. fulvus adults/plant is also presented.

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