Effects of Weeds on the Diversity and Abundance of Insects in Soybeans

Mark D. Shelton, California Polytechnic State University - San Luis Obispo
C. R. Edwards, Purdue University - Main Campus

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Abstract

Sweep-net sampling and pitfall trapping were used to survey insects in weedy and weed-free soybean habitats. Weedy soybean habitats consisted of (1) grassy soybeans; (2) soybeans with broadleaf weeds; and (3) soybeans with broadleaf weeds and grasses. Insect species diversity was greater in weedy soybean habitats than in weed-free soybeans. Greatest diversity of species occurred in the mixed-weed soybean habitat. The most important phytophagous insect on soybeans in Indiana, the Mexican bean beetle, Epilachna varivestis Mulsant, was most abundant in weed-free soybeans. Predators were most ahundant in weedy soybeans. Coleomegilla maculata (DeGeer) was most abundant in weedy soybean habitats, whereas Orius insidiosus (Say) and Nabis spp. were most abundant in soybean habitats with grasses and mixed weeds. In the pitfall trapping study, Harpalus spp. were more abundant in soybean habitats with grasses and mixed broadleaf and grass weeds.