Feeding Behavior and Egg Maturation of the Red and Gray Sunflower Seed Weevils (Coleoptera: Curculionidae) on Cultivated Sunflower

Abstract

Adult gray and red sunflower seed weevils, Smicronyx sordidus LeConte and Smicronyx fulvus LeConte, respectively, are pests of sunflower, Helianthus annum L., and use the plant as food and an oviposition site. The evolved behavior of these weevils minimizes competition for food and oviposition sites on the sunflower plant. Both male and female S. sordidus fed more on leaves of sunflower hybrid ‘894’ than on disk flowers. Mature eggs developed when females were given access to prebloom R1-R3 stage sunflower plants. Females feeding only on blooming capitula did not develop mature eggs even after 12d. S. fulvus females fed more on sunflower hybrid ‘894’ disk flowers than on leaves or bracts; males fed more on disk flowers and leaves than on bracts. Females exposed to prebloom stages (R1-R4) did not produce mature eggs, but did so when access was prolonged until bloom stage (R5.1). Females confined in blooming capitula developed mature eggs after 4d. Pollen stimulated egg maturation only when mixed with other foods such as ground sunflower seed, sucrose, or water. The preference of each weevil species for a particular sunflower plant tissue, organ, or structure, and growth stage for feeding and reproduction may be useful in developing efficient management strategies for these sunflower pests.