Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/20/2012
Publication Date: 2/1/2012
Citation: Follett, P.A., Snook, K., Janson, A., Antonio, B., Haruki, A., Okamura, M., Bisel, J. 2012. Irradiation quarantine treatment for control of Sitophilus oryzae (Coleoptera: Curculionidae) in rice. Journal of Economic Entomology. Interpretive Summary: • Irradiation is a control option for stored product insects • Rice weevil is the most serious pest of stored rice worldwide • Adult and immature weevils were treated at 0, 30, 60, 90 or 120 Gy in rice • Radiation treatment at 120 Gy sterilized rice weevil and prevented further damage • Irradiation can prevent the spread of phosphine-resistant weevils in exported grain
Technical Abstract: Irradiation is a quarantine treatment option for stored products pests. Dose response tests were conducted to identify a postharvest radiation treatment that would control rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) in rice. Rice infested with adult or immature weevils was treated at radiation doses of 30, 60, 90, or 120 Gy, or left untreated as a control, and live and dead beetles were counted weekly for 14 to 25 weeks. Treatment of adult weevils at a radiation dose of 120 Gy resulted in no live adults after two weeks, indicating that this radiation dose caused adult mortality and sterility, whereas a total of 1261 adult beetles emerged during 25 weeks in the untreated controls. Treatment of immature life stages (a mixture of eggs, larvae and pupae) with a radiation dose of 90 or 120 Gy resulted in no adults emerging after five or two weeks, respectively, indicating that these doses prevented reproduction, whereas a total of 4275 adults emerged throughout 14 weeks in the untreated controls. Weight loss of rice infested with immature or adult weevils was significantly reduced by irradiation treatment at 60 Gy and 120 Gy. In a large-scale confirmatory test, a radiation dose of 120 Gy applied to 38,025 adult weevils in rice resulted in no reproduction. Irradiation at 120 Gy will provide quarantine security for rice weevil, and prevent post-irradiation weight loss caused by insect feeding in the commodity. Irradiation may be particularly helpful in controlling phosphine-resistant populations, and will help manage resistance by preventing the spread of resistant weevils in exported grains.