Mortality and Progeny Production of Several Stored Grain Beetle Pests in Shelled Corn Treated with Entrust®

Use of synthetic chemicals has been the primary method of insect control in stored grain. Concern for insecticide resistance, chemical residues, environmental contamination, and worker exposure has lead to development of biologically based insecticides such as Spintor® 2SC. Spintor has been found to be effective against several stored grain beetle species on wheat and shelled corn in storage. Recently it was re-formulated to conform to OMRI national standards and is now commercially available as an organic insecticide (i.e., Entrust®) registered for use on fruits and vegetables. However, no information regarding the use of Entrust on stored grains has been found. A laboratory study was conducted to determine efficacy of Entrust on maize weevil (Sitophilus zeamais Motsculsky), red flour beetle (Tribolium castaneum (Herbst)), and sawtoothed grain beetle (Oryzaephilus surinamensis (Linnaeus)) infesting stored shelled corn. Shelled corn was treated with 1 ppm or 3 ppm of Entrust or left untreated. Mortality was quantified at 1, 3, and 7 days after exposure. Maize weevil survival was negatively affected at all three time intervals at both the 1 ppm and 3 ppm treatments with 100% mortality observed after one week for the 3 ppm treatment. No significant differences in mortality were seen between treated and control groups of either sawtoothed grain beetle or red flour beetle. However, Entrust treated corn negatively affected progeny emergence of all three insect species.