Control of R. dominica in stored rough rice 455

Control of Rhyzopertha dominica in stored rough rice through a combination of diatomaceous earth and varietal resistance Abstract Adults of Rhyzopertha dominica (F.), the lesser grain borer, were exposed on four varieties of rough rice with Dobie indices of susceptibility of 1.1 to 1.1 (low), and four varieties with Dobie indices of susceptibility of 3.4 to 3.8 (high). The varieties with low and high Dobie indices were classified as resistant and susceptible, respectively, to R. dominica. The purpose of the study was to evaluate control of R. dominica through the use of diatomaceous earth (DE) in combination with rice varieties that were either susceptible or resistant to R. dominica. The rice was treated with varying rates of the commercial DE Insecto®, up to a maximum of 1 000 mg DE/kg of rice. Adult mortality at each application rate of DE was generally greater on three of four resistant varieties compared to three of four susceptible varieties. Progeny production from the parental generation exposed on the rice was also greater in 3 of the 4 resistant varieties compared to 3 of the 4 susceptible varieties at DE rates of 500 mg/kg or more. Progeny production in rice treated with a maximum rate of 1 000 mg/kg DE ranged from 7-44 adults on the resistant varieties compared to 75-15