The fate and effectiveness of spinosad, a reduced-risk bacterial pesticide, was evaluated by placing spinosad-treated hard red winter wheat samples just below the surface of farm-stored grain. Hard red winter wheat, from three grain bins were treated separately to obtain the following spinosad rates: 0, 0.1, 0.5, 1.0, 3.0, 6.0 mg of spinosad active ingredient (AI) per kg of wheat. Each untreated and spinosad-treated wheat samples (250 g) were placed in 3 plastic mesh pouches of two different mesh sizes. One set of meshes had wider opening to allow insect entry, but prevent kernels from fall through the holes. The other two sets had smaller openings that prevented entry of adult insects. Pouches were placed 2-3 cm below the grain surface in each of the 3 bins at 6 different locations. Temperatures and relative humidity at each location were monitored with 2 HOBO units. Pouches were removed every other month starting November 2001. Ten probe traps were places in each bin to capture insects colonizing the grain surface. Wheat in pouches with the larger mesh was used to determine number of insects present and grain damage. One set of the smaller mesh samples was brought to the laboratory to expose adults of the less grain borer and red flour beetle for 14 d to determine mortality. Wheat in the other set from all 3 bins was pooled and submitted to Dow AgroSciences for residue analysis. Few insects were found in the Jan., Mar., and May samples and the probe traps. In the laboratory, spinosad killed all lesser grain borer during first 4 sampling occasions, whereas the mortality of the red flour beetle adults increased with the rate and 100% mortality occurred only at the 6 mg/kg rate. The poster will contain additional data beyond July 2001, including the residue analysis.
Species 1: Coleoptera Bostrichidae Rhyzopertha dominica (Lesser grain borer)
Species 2: Coleoptera Tenebrionidae Tribolum castaneum (red flour beetle)
Keywords: spinosad, grain protectant
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA