Determination of Hidden Sitophilus granarius (Coleoptera: Curculionidae) in Wheat by Myosin ELISA

Abstract

The myosin content of wheat containing immature Sitophilus granarius (L.) was measured using a color-detected immobilized immunological assay (sandwich ELISA), calibrated with myosin extracted from Acheta domestica (L.) legs. The myosin was tested in blind tests as a function of insect count and insect stage in 50 g-wheat samples. Myosin content rose from 0.1 to 9.0 µg per insect from first to fourth instar, dropped to 1.9µg per insect in the pupal stage, and rose to 6.6 µg per preemergent adult for an overall average of 5.5 µg per X-ray-detectable insect. This variation is similar to that noted previously for externally feeding immature insects. A background level equivalent to 6.8 µg per 50 g wheat was observed. This ELISA approach shows promise as a sensitive method for detecting hidden insects (immature insects developing within the kernel) in wheat at a level of interest for wheat acceptance at flour mills, approximately six insects per 50 g wheat, with a standard deviation of ± 0.8 insects.