Protecting Rough Rice Stored in Metal Farm Bins from Insect Attack1

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Abstract
U.S. No. 1 grade rough rice was stored in galvanized metal bins and monitored for 12 months to determine insect infestation and quality factors. Six treatments—malathion, aeration, a combination of malathion and aeration, pirimiphos methyl, chlorpyrifos methyl, and controls—were tested. After 6-months storage, dichlorvos strips were compared to phosphine fumigation for moth control in selected bins. Heavy infestations of Angoumois grain moths, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae) and lesser grain borers, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) developed in all untreated rice and in all rice treated with malathion. One replicate treated with pirimiphos methyl became infested with lesser grain borers. Two replicates treated with pirimiphos methyl and all replicates treated with chlorpyrifos methyl remained free from infestation for 12 months. Fumigation with phosphine reduced an infestation of Angoumois grain moths ca. 99% but the population began to recover immediately after treatment. A dichlorvos strip suspended in the overspace reduced the infestation ca. 99% within six weeks and eliminated it by 12 weeks. Infestations that were not controlled resulted in severe quality damage. In some cases, the rice quality was reduced to U.S. sample grade in 12 months.