POPULATIONS OF FOLIAGE-INHABITING ARTHROPODS ON SOYBEAN WITH REDUCED TILLAGE AND HERBICIDE USE

Modification of tillage and herbicide use patterns to reduce adverse e nvironmental effects on soybean [Glycine max (L.) Merr.] production ma y impact arthropod populations and damage in soybean. The objectives o f this held study were to examine the effect of reduced tillage and he rbicide use on populations of foliage-inhabiting phytophagous and bene ficial arthropods and their damage in soybean. Tillage treatments of n o-tillage, chisel-plow with disking, and moldboard plow with disking a nd herbicide regimes of high (preplant and postemergence control), red uced (postemergence control), and no herbicide use were established in a 2-yr rotation of corn (Zea mays L.), winter wheat (Triticum aestivu m L.), and soybean. Phytophagous and predatory arthropods were sampled from soybean foliage with the shake-cloth technique throughout the se ason in 1988, 1990 and 1992. Tillage treatments did not consistently a ffect any arthropod groups except stink bugs (Pentatomidae), which wer e more abundant in no-tillage than plow-tillage treatments, and bigeye d bugs (Geocoris spp.), which were more abundant in both plow-tillage treatments than in no-tillage. Herbicide regime also had no consistent effect on abundance of any taxa. Additionally, tillage and herbicide regimes had little consistent effect on soybean lepidopteran defoliati on and pod damage caused by the bean leaf beetle [Cerotoma trifurcata (Forster)] over the 3 yr. There were extensive stand losses due to rod ent damage (cotton rat; Sigmodon hispidis Say & Ord) in the no-tillage , no-herbicide system in 1992, where crabgrass [Digitaria sanguinalis (L.) Scop.] was prevalent. These results suggest that tillage and herb icide use practices can be modified without greatly affecting arthropo d populations and their damage in soybean. However, these results impl y that the potential for managing arthropod populations by modified ti llage and herbicide use is limited in soybean.