Efficacy and economics of fresh-market Bt transgenic sweet corn in Virginia

The effectiveness and cost of managing the suite of insect pests that attack sweet corn in Virginia were evaluated using multiple foliar applications of pyrethroid insecticides and Bt transgenic sweet corn in 2000 and 2002. Several Bt cultivars and their non-transgenic isolines were tested in different locations in Virginia to examine efficacy over a range of growing conditions and pest pressure. Overall, insect damage was far less in the Bt cultivars than in the non-Bt isolines that were not sprayed or sprayed with lambda-cyhalothrin up to six times. When insect pressure was low to moderate, Bt sweet corn did not require supplementary insecticide applications for a high percentage (⩾88%) of ears to be considered fresh-market quality. In contrast, when insect pressure was extremely high, Bt sweet corn required two insecticide applications for a high percentage (⩾88%) of ears to be considered fresh-market quality. Based on an economic comparison between insecticide-treated conventional sweet corn and Bt sweet corn, growers should expect a $547/ha gain by growing Bt sweet corn. If Bt sweet corn was sprayed twice with an insecticide, this gain should be approximately $1777/ha. We conclude that Bt sweet corn is an effective and economically sound pest management strategy for growers in Virginia.