A Comparison of Three Sampling Methods for Arthropods in Soybeans1

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Abstract
Sweep-net, D-Vac®, and ground-cloth sampling methods were compared by taking weekly samples of insect pests and beneficial arthropods associated with soybeans from Aug, 2–Sept. 26, 1972. Sample means were derived from 20 samples from each of 3 one-acre soybean fields. Generally with all 3 sampling procedures, samples having low mean numbers yielded higher coefficients of variability. Linear regression of coefficients of variability on the sample means revealed high correlations, and analysis of covariance on weighted means revealed no significant difference among D-Vac, sweep, and ground-cloth sample methods. The ground-cloth method produced higher means for most of the species collected in this study (spiders, Geocoris spp. nymphs, Nabis spp. nymphs, large larvae of Plathypena scabra (F.), and larvae of Heliothis spp., Trichoplusia ni (Hübner), Pseudoplusia includens (Walker), and Epilachna varivestis Mulsant. The 3 methods were equally effective in sampling adults of geocorids and nabids. Larvae of P. scabra were sampled more effectively by the sweep-net method. D-Vac samples consistently gave very low population estimates of all lepidopterous species.

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