Management of a Stem Weevil, Cylindrocopturus adspersus (LeConte) (Coleoptera: Curculionidae), in Sunflower in the Southern Great Plains1

Abstract

The application of chemical insecticides to sunflower, Helianthus annuus L., infested by Cylindrocopturus adspersus (LeConte) caused significant reductions (5% level) of larvae in stalks, but it did not result in increased seed yield in treated plants. Fall and winter disking or sweep plowing of sunflower to disrupt and destroy roots and lower stalks harboring overwintering C. adspersus at Bushland, Tex., did not increase the mortality of overwintering larvae. Each 2- to 3-week delay in the planting of sunflower at Bushland resulted in a significant decline (5% level) in the number of C. adspersus larvae infesting the stalks. Concurrent delays in the planting of sunflower until late Mayor early June caused no significant reduction of either seed yield or seed oil content. Therefore, we conclude that delayed planting of sunflower in the southern Great Plains is a management strategy that may be used to significantly reduce or escape economic losses in sunflower due to stalk injury by larvae of C. adspersus.