The Potential of Bt Corn as a Trap Crop for the Control of Corn Earworm, Helicoverpa zea Boddie, in Soybean

Abstract

ABSTRACT Corn and soybean are two important crops in the Delmarva (Delaware, Maryland and Virginia) peninsula region. Both crops are attacked by corn earworm (CEW), Helicoverpa zea (Boddie). The larvae cause significant ear damage to corn serving as a primary nursery for CEW populations which shift to soybean later in the season. In soybean, CEW larvae cause serious yield losses if not controlled by insecticides. Many farmers in the Delmarva region have been increasing the acreage they grow with genetically engineered corn hybrids that contain insecticidal proteins expressed by the genes of Bacillus thurngiensis sub sp. kurstaki (Bt) as an alternative to the application of chemical insecticides. A study was conducted to investigate the use of Bt corn as a trap crop for the management of CEW in soybean. Bt corn was planted as a trap crop in a ten percent of the area of soybean as a peripheral trap, trap in the middle and trap in the intermittent rows in soybean. CEW moths were attracted and observed on the newly formed silks of the ears of Bt corn in all types of traps including peripheral trap, trap in the middle and trap in the intermittents rows planted in soybean. CEW eggs were also observed on the silk of transgenic corn. The moths, eggs and larvae (CEW) were hardly observed in soybean grown as a main crop. Clearly, we were able to divert the CEW adults on Bt corn from soybean. The number of CEW eggs was significantly higher in the peripheral trap and trap in the intermittent rows compared with trap in the middle of the plots, suggesting that Bt corn planted as a peripheral trap crop could be more practicable and effective for the farmers in reducing the CEW damage in soybean.