Data were taken on 12 to 15 farms in the Mississippi Delta from 1997 through 2000 to measure the entomological and economic impact of Bt cotton when compared with conventional cotton. Data from 1997 showed that insect control costs were slightly less for conventional cotton. In 1998, data showed that in the face of a heavier tobacco budworm problem, there was a significant reduction in insect control costs for Bt cotton. In 1999, all cotton insect problems were very low and the data indicated a smaller cost for insect control in conventional cotton. In spite of the extremely unfavorable weather conditions (drought and heat), yield and cost of insect control were not significantly different from other years in 2000 with no significant difference in either yield or cost between Bt and conventional cotton.

The profitability of Bt cotton is a function of the severity and duration of tobacco budworm infestations in any given year and to a lesser extent this is true for cotton boll worm. The problems associated with tobacco budworm infestations in 1995 are always a threat, and it appears that cotton growers should always plant some Bt cotton varieties. The amount they plant should probably be based on the history of tobacco budworm infestations associated with the producer’s farm.