Determining the relationship between boll age and green plant bug feeding injury to South Texas cotton

Authors: Armstrong, John; Adamczyk, John; Coleman, Randy

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/29/2009
Publication Date: N/A
Citation: N/A

Interpretive Summary: A green plant bug 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. Threatening infestations have only developed post-bloom, with the greatest damage potential occurring when bolls are young. Cotton producers and crop managers have asked for information on when it would be economically feasible to stop making management decisions (i.e. insecticides applications) later in the season when bolls are reaching maturity. This boll-age/damage relationship has been established for some other plant bugs and stink bug pests of cotton and proven useful in reducing unneeded insecticide applications. We propose to define the relationship of boll-age and feeding injury, and provide a degree-day based threshold that will identify when insecticides are no longer required to protect seed and fiber quality. The 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. The collaborators (i.e. EA-IPM’s) listed on this proposal will also provide timely information to producers on the developed threshold.

Technical Abstract: Our objectives are to define the relationship of feeding-injury of the green plant bug, Creontiades signatus (Stahl), to cotton boll age to 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 (Stahl) (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) - 60 F) are commonly used and available from different sources where crop managers could easily determine the threshold. We tagged cotton blooms in the summer of 2008, and infested them with a green plant bug at a range of accumulated DD’s between 100 and 500 heat units. The bolls were collected at maturity where seed cotton weight, lint weight and seed weight were recorded. Regression analysis was performed on the heat unit accumulations (independent variables) and the yield parameters (dependant variables) to define relationships, and identify the number of DD’s required before feeding injury will no longer occur. Boll abscission was 35% for up to 100 DD’s, 11% for bolls between 100 and 200 DD’s, 2% for bolls between 200-300 DD’s, and none for bolls over 300 DD’s. Lint and seed yields were reduced from C. signatus feeding up to 250 DD’s from white bloom.