D3076: Control of Rhyzopertha dominca through stored grain protectants

Rice growers are increasingly storing their harvests in on-site grain bins for extended periods, exacerbating the impacts of stored grain pests. Fumigants have been the most common form of pest management in stored grains, but concerns over resistance are driving the development of alternative methods for controlling stored rice pests. Here, we investigated five grain protectant insecticides: methoprene, deltamethrin, a commercial formulation of methoprene with deltamethrin, diatomaceous earth, and beta-cyfluthrin. Treatments and a control were applied to rice stored in 5-gallon trash bins (N=50). Then, 50 lesser grain borers, Rhyzopertha dominica, and 50 rice weevils, Sitophilus oryzae, were added to each bin every month. To assess product efficacy, each month a grain probe sample was taken from each bin, and beetles were counted. Additionally, vials of rice were removed from each bin each month. Ten R. dominica or S. oryzae were added to each vial. After 2 weeks, beetle mortality was calculated for each vial, and after 8 weeks, progeny were counted. After 6 months, the frass and beetle biomass of each grain bin was weighed. Control of beetles varied widely between treatments, signifying the importance of using effective insecticides to mitigate rice damage and manage pest populations.