Efficacy of two amorphous silica powders applied to soft red winter wheat against the lesser grain borer, Rhyzopertha dominica (Fabricius)

Amorphous silica powders 1 and 2 with different elemental composition, were procured from Imerys Chemicals, Lompoc, California, and applied to wheat to determine efficacy against the lesser grain borer, Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae). The efficacy of the two powders was determined by exposing 25 adults to 100 g of wheat treated with 0, 0.05, 0.1, 0.15 and 0.20 g/kg. Mortality assessment was made after 14 d, and data on adult progeny production, insect damaged kernels and weight loss for each powder-concentration combination were recorded after 42 d. Percentage mortality, adult progeny production, number of insect damaged kernels and weight loss data were subjected to one-way ANOVA and mean separations were done using REGWQ procedure. Complete mortality of R. dominica adults was not achieved at any silica powder 1 concentrations; however, 100% mortality was observed on wheat treated with 0.20 g/kg of silica powder 2. Adult progeny production of R. dominica was completely inhibited by silica powder 2 concentration of 0.20 g/kg, whereas progeny production was not wholly suppressed at any silica powder 1 concentrations. Insect damaged kernels and weight loss was not observed when adults of R. dominica were exposed to wheat treated with 0.15 and 20 g/kg concentrations of silica powder 2. Silica powder 2 was consistently more efficacious than silica powder 1, and the greater efficacy of silica powder 2 can be attributed to its higher oil absorption capability.