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United States Department of Agriculture

Agricultural Research Service

Research Project: ECOLOGY, SAMPLING, AND MODELING OF INSECT PESTS OF STORED GRAIN, PROCESSING FACILITIES, AND WAREHOUSES Title: Efficacy of Spinosad in Layer-Treated Wheat Against Five Stored-Product Insect Species

Authors
item Athanasiou, Christos
item Arthur, Franklin
item Throne, James

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 17, 2009
Publication Date: October 1, 2009
Repository URL: http://doi:10.1016/j.jspr.2009.04.002
Citation: Athanasiou, C.G., Arthur, F.H., Throne, J.E. 2009. Efficacy of Spinosad in Layer-Treated Wheat Against Five Stored-Product Insect Species. Journal of Stored Products Research 45: 236-240.

Interpretive Summary: In bulk grains, most of the insect infestation occurs in the top layer of the grain mass so we evaluated the effectiveness of a new biological insecticide spinosad as a surface treatment in wheat to control adults of five common species of stored-grain insect pests. Spinosad was applied to the upper one half, one fourth, or one eighth layer of the wheat or the entire grain mass in a vial, and insects were either added to the vials before or after the wheat. When lesser grain borers were added to the vials after the wheat, all insects died except in the one-eighth layer treatment. In contrast, when adults were placed in the vials before the wheat, all insects died only when all of the wheat was treated. Mortality of the rice weevil was lower but there was evidence of upward movement into the treated layers. Mortality of the psocids Liposcelis paeta and L. bostrychophila was <50% when the entire quantity was treated, in contrast to 100% mortality of the psocid Lepinotus reticulatus. However, for all psocid species, overall mortality decreased with decreasing depth of the treated layer. The results of this laboratory study show that while spinosad has some effectiveness as a partial treatment to wheat, efficacy will depend on the target species, the depth of the treated layer, and the upward or downward mobility of the insect species.

Technical Abstract: The biological insecticide spinosad was evaluated in laboratory bioassays as a surface treatment in wheat to control adult Rhyzopertha dominica (F.), Sitophilus oryzae (L.), and three psocid species, Liposcelis paeta (Pearman), L. bostrychophila (Badonnel), and Lepinotus reticulatus (Enderlein). Spinosad was applied at 1 ppm to 35 g wheat placed in a vial or to the upper one half, one fourth, or one eighth layer of the wheat, and insects were either added to the vials before or after the wheat. When R. dominica were introduced into the vials after the wheat, mortality was 100% except for 83% mortality in the one-eighth layer treatment. In contrast, when adults were placed in the vials before the wheat, mortality was 100% only when all of the wheat was treated. Mortality of S. oryzae was lower compared to R. dominica but there was some evidence of upward movement into the treated layers. Mortality of L. paeta and L. bostrychophila was <50% when the entire quantity was treated, in contrast to 100% mortality of L. reticulatus. However, for all psocid species, overall mortality decreased with decreasing depth of the treated layer. The results of this laboratory study show that while spinosad has some effectiveness as a partial treatment to a column of wheat, efficacy will be dependent on the target species, the depth of the treated layer, and the upward or downward mobility of the insect species.

Last Modified: 12/21/2014
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