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

Modification of tillage and herbicide use patterns to reduce adverse environmental effects on soybean [Glycine max (L.) Merr.] production may impact arthropod populations and damage in soybean. The objectives of this held study were to examine the effect of reduced tillage and herbicide use on populations of foliage-inhabiting phytophagous and beneficial arthropods and their damage in soybean. Tillage treatments of no-tillage, chisel-plow with disking, and moldboard plow with disking and herbicide regimes of high (preplant and postemergence control), reduced (postemergence control), and no herbicide use were established in a 2-yr rotation of corn (Zea mays L.), winter wheat (Triticum aestivum L.), and soybean. Phytophagous and predatory arthropods were sampled from soybean foliage with the shake-cloth technique throughout the season in 1988, 1990 and 1992. Tillage treatments did not consistently affect any arthropod groups except stink bugs (Pentatomidae), which were more abundant in no-tillage than plow-tillage treatments, and bigeyed 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 defoliation and pod damage caused by the bean leaf beetle [Cerotoma trifurcata (Forster)] over the 3 yr. There were extensive stand losses due to rodent 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 herbicide use practices can be modified without greatly affecting arthropod populations and their damage in soybean. However, these results imply that the potential for managing arthropod populations by modified tillage and herbicide use is limited in soybean.