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Abstract

To evaluate the effects of soybean trap crops and maize barrier crops on the occurrence of and damage caused by pentatomid bugs and lepidopterous pod borers in soybean fields, the suitability of early maturing cultivars of soybean (Glycine max) and dent maize (Zea mays ssp. dentata) to protect medium- and medium-late-maturing cultivars of soybean were investigated in 1999 and 2000. Five species of Pentatomidae, Riptortus clavatus, Piezodorus hybneri, Halyomorpha mista, Plautia stali, and Nezara antennata, were observed in the soybean fields during August and September. The population of N. antennata was very small in both years. The numbers of R. clavatus, P. hybneri, and H. mista were relatively constant in both years, but the numbers of P. stali differed between years. R. clavatus and P. hybneri did not aggregate on the trap crops. In August 1999, P. stali were crowded on the trap crops and subsequently moved to the field crops. There was no difference in the damage caused by pentatomids between the soybean blocks separated by the barrier crop, except the damage at the early developmental stage of seeds in 1999. These results suggest that neither trap crops nor barrier crops are effective in controlling pentatomids, though they may be suitable for monitoring P. stali. On the other hand, the barrier crops had an effect on the damage caused by lepidopterous pod borers in both years. Especially in 1999, the soybean crops surrounded by the barrier crop showed as little damage as crops that had been sprayed twice with an insecticide (fenvalerate+fenitrothion). This result indicates a usefulness of barrier crops for control of lepidopterous pod borers. However, the effectiveness of the barrier crops must be investigated further.