Impact of cotton tillage systems on in-season and overwintering survival and emergence of Heliothis virescens

Cotton has been used as a fabric for thousands of years, and today cotton Is an important crop grown in the United States with more than 6,000,000 hectares planted in 1996. Cotton is not indigenous to the United States and was relatively free of insect pests until the boll weevil was found in Texas in 1892. Extensive use of calcium arsenate for control of the boll weevil up to 1945 is correlated with the tobacco budworm, Heliothis virescens (F.), emergence as a pest species. Tobacco budworms cause damage to cotton by feeding on the fruiting structures of the plant. Approximately 15 d after hatching, larvae stop feeding, move downward and tunnel into the soil, forming a cell in which they change to the pupal stage. Research was conducted at the West Tennessee Experiment in 1997 and 1998 to evaluate the impact of tillage systems on the survival and emergence of tobacco budworm. The objectives of this research were to: 1) determine the impact of tillage on in-season emergence and survival of tobacco budworm and to understand the influence of climatic conditions, 2) determine the impact of tillage on overwintering emergence and survival of tobacco budworm and to understand the influence of climatic conditions. The two tillage treatments for this research were a total no-till production system and a double disked treatment at planting with subsequent weed flushes controlled with herbicides. The double disked treatment was conducted just prior to planting for the in-season study and the previous spring for the overwintering study. In all of the in-season cohorts a higher percentage of moths emerged in the no-till system, but this difference was not statistically significant at the p<.05 level. More moths emerged later in the growing season and there was significant differences between the different infestation date cohorts. Two variables, degree day-60's, and precipitation, explained 60% of variation in emergence percentage, and these were significant at the p<.05 level. There were no significant differences in emergence percentage between the two tillage treatments in the overwintering study. Precipitation, days that the temperature reached 0°C , and duration from infestation to emergence in d were studied to find any significant influences on spring emergence percentage. None of these environmental factors significantly influenced emergence percentage. This research indicated that very low numbers of tobacco budworm can successfully overwinter in cotton fields independent of tillage system. Crop growth and precipitation also influence tobacco budworm emergence more than tillage system during the growing season. A producer can continue to utilize a no-till cotton production system and receive this systems benefits without increasing tobacco budworm numbers.