Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2002
Publication Date: 2/1/2003
Citation: Arthur, F.H., Throne, J.E. 2003. Efficacy of diatomaceous earth to control internal infestations of rice weevil and maize weevil (Coleoptera: Curculionidae). Journal of Economic Entomology. 96(2):510-518. Doi: http://dx.doi.org/10.1603/0022-0493-96.2.510. Interpretive Summary: When stored grains are infested with insects that feed inside the kernels, fumigation of the entire grain mass is usually the recommended control method. However, in many instances the infestation is isolated on the grain surface, and could potentially be controlled by a spot or local treatment. Diatomaceous earth, or DE, is a natural product used as a grain protectant. Wheat and corn kernels infested with immature grain weevils were mixed in with uninfested kernels treated with DE. Once the adult weevils emerged from the kernels they were killed by exposure to the DE, but some weevils were able to lay eggs before they died. Results show that an application of DE to infested grains could help suppress the infestation and perhaps avoid the need to fumigate the entire grain mass.
Technical Abstract: Hard red winter wheat kernels, Triticum aestivum L., were infested with different life stages of the rice weevil, Sitophilus oryzae (L.), mixed in with 35 g of wheat treated with 300 ppm of the Protect-It formulation of diatomaceous earth (DE), and held at 22, 27, and 32 degrees C. A similar test was conducted by exposing corn kernels infested with different life stages of the maize weevil, Sitophilus zeamais Motschulsky, mixed in with 30 g of corn, Zea mays L., treated with 300 ppm of DE. Mortality of adults emerging from kernels in wheat treated with DE was always greater than controls, and ranged from 56 to 90% at 22 degrees C and was greater than 90% at 27 and 32 degrees C. In most treatment combinations, exposure to the DE suppressed F1 progeny at levels of 60 to 90% relative to untreated controls. Mortality of adult maize weevils on treated corn held at 22 and 27 degrees C was lower than mortality of rice weevils on wheat, and ranged from 4 to 84%. F1 production was low in corn held at 22 degrees C, and no F1s were produced in either the controls or the treatments at 32 degrees C. In treated corn held at 27 degrees C, exposure to the DE suppressed F1 progeny at levels of about 70 to 80% relative to the untreated controls. Results of this study show that rice weevils and maize weevils emerging from infested kernels as adults were susceptible to DE. Application of DE to commodities already infested with internal feeders such as the rice weevil and the maize weevil could help in eliminating or suppressing the infestation.