Efficiency of conventional sampling methods for determining arthropod densities in close-row soybeans

Relative efficiencies of sweep-net, vertical beat sheet, and ground cloth s ampling methods for soybean [Glycine max (L.) Merrill] arthopods were evalu ated by relative net precision criteria in close-row (drilled) soybeans and in conventionally planted soybeans. Accuracy and precision were determined by fidelity of relative sample means to arthropod means from an absolute m ethod. Fidelity to absolute population density was high in both drilled and conventional soybeans for all relative methods except the sweep-net for so ybean loopers, Pseudoplusia includens (Walker). The ground cloth method pro vided the highest degree of accuracy in both field types, but the sweep-net showed a comparable degree of fidelity for common pests in drilled fields. Precision of sampling methods in drilled soybeans, determined by direct co mparisons of relative variation of samples for each of the sampling techniq ues, was best for the sweep-net for pentatomids and velvetbean caterpillar, Anticarsia gemmatalis Hubner. The ground cloth yielded lower relative vari ations than other methods for lepidopterous larvae in conventional soybeans . For all arthropod species in drilled soybeans, exclusive of soybean loope rs in both years, the sweep-net method resulted in a, higher relative effic iency (higher relative precision per unit of cost) than the ground cloth an d vertical beat sheet because the cost was low in work-hours required to ob tain a satisfactory level of accuracy and precision.