Field Crops News

Tilling and Herbicides Affect Predator Abundance in Soybeans

The use of no-till in soybeans is increasing in the Midwestern United States. However, not much is known about the effects of no-till and herbicides on soil-dwelling predators, such as ground beetles and spiders, which are potential biological control agents of crop insect pests. A 1994 study in Ohio examined the effects of tillage and the use of herbicides on various predators that live on the soil surface in soybean fields. Four treatments were set up in large plots (about an acre in size): no tillage without herbicides, no-tillage with herbicides, conventional tillage without herbicides, and conventional tillage with herbicides. Pitfall traps were used to collect predators in the plots and estimate their relative numbers.

There were more ground beetles in tilled plots not treated with herbicides than in the other plots. Certain spiders were less abundant in tilled plots treated with herbicides. Centipedes were more numerous in tilled plots. Although there were fewer predators in the no-tillage treatments in this one-year study, the accumulation of litter in no-till plots over time may eventually provide more suitable habitats and alternate prey for ground-dwelling predators. The benefits supplied to the predators by no-tillage soybean systems may lead to increased control of pest insects because of larger predator populations.

- Daniel Pavuk, Ann Rypstra, and Samuel Marshall, Bowling Green State University, Ohio

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