Sampling plans for the psocids Liposcelis entomophila and Liposcelis decolor (Psocoptera: Liposcelididae) in steel bins containing wheat.

Psocids are an emerging problem in grain storage, handling, and processing facilities in the United States. We used data from two steel bins each containing 32.6 metric tonnes of wheat, Triticum aestivum L., to develop sampling plans for Liposcelis entomophila (Enderlein), Liposcelis decolor (Pearman) (both Psocoptera: Liposcelididae), and a mixture of the two species. Taylor's coefficients a (a sampling factor) and b (an index of aggregation) for these pests were calculated and incorporated into sampling protocols to improve accuracy. The optimal binomial sample sizes for estimating populations of these psocids at densities of < 25 psocids per refuge were large; therefore, we recommend the use of numerical sampling within this range of densities. Numerical sampling of L. entomophila and L. decolor at densities of < 25 psocids per refuge should not be too laborious given the low psocid numbers involved; we recommend using 10 refuges per bin. For presence-absence sampling of L. entomophila or L. decolor, 20 refuges per bin should be used at densities of 25-100 psocids per refuge. The sampling plans we have developed based on the use of cardboard refuges are convenient for use in steel bins containing wheat because they are inexpensive, provide a rapid assessment of psocid population incidence, and are easy to implement. These sampling plans can be used to monitor populations of and the efficacy of management strategies used against L. entomophila and L. decolor.