Determining the Relationship Between Boll Age and Green Plant Bug Feeding Injury to South Texas Cotton

Our objectives are to define the relationship of feeding-injury of the green plant bug (Creontiades signatus) to cotton boll-age; this will provide a degree-day-based threshold that determines when economic damage no longer occurs so that management (i.e. insecticides applications) can be justifiably terminated. Creontiades signatus (Heteroptera: Miridae) has been infesting cotton in the Coastal Bend and the Lower Rio Grande Valley of Texas in high enough densities that insecticide treatments have been applied to reduce feeding damage, even though an economic threshold has not been established. Accumulated heat units (daily max – min/2 minus 60 F) are commonly used and available from different sources where crop managers could easily determine the threshold. We tagged cotton blooms, and infested them with a single green plant bug when accumulated DD’s reached from 100, 200, 300 and 500 heat units. The bolls were collected at maturity and assigned a damage score, seed-cotton weight, lint weight and seed weight, and the number of damaged and undamaged ovules will be noted. Regression analysis will be performed on the heat unit accumulations (independent variables) and the yield parameters (dependant variables) to determine relationships, and identify the DD accumulation where feeding injury will no longer occur. Analysis of variance and repeated measures analysis will be performed on the damage score, seed-cotton weight, lint weight and seed weight, and the number of damaged and undamaged ovules to determine if significant differences occur across accumulated DD’s.