Project Summaries

11-955  Project Manager: P. F. O'Leary

REGIONAL THRIPS TRIALS, BOLLWORM RESISTANCE AND IMPACT OF BROWN MARMORATED STINK BUG ON COTTON BOLLS

D. Ames Herbert, Virginia Polytechnic Institute and State University

The objectives of the regional thrips trials (Objectives 1-3) were to examine how a seed treatment and the addition of starter fertilizer may reduce observed thrips injury on seedling cotton in the southeastern United States; to evaluate efficacy of foliar insecticides for managing thrips on seedling cotton; and to evaluate different rates of Cyazypyr and Radiant SC on top of a seed treatment for managing thrips on seedling cotton. Objective 4 was to monitor resistance potential in bollworm (Helicoverpa zea) moths using adult vial tests with a standard pyrethroid insecticide (cypermethrin). Objective 5 was to assess brown marmorated stink bug (BMSB) (Halyomorpha halys) injury to cotton through the use of cage studies.

Results of Objective 1 are being provided in the Beltwide Cotton Conferences Proceedings (see below). From Objective 2 we learned that two foliar broadcast insecticide applications with products such as Benevia can significantly reduce thrips populations and thrips injury levels, while pyrethroids (e.g., Karate) do not. In Objective 3, efficacy of seed treatments (containing a base fungicide and Cruiser) was enhanced with the addition of a single foliar broadcast application of Benevia, Orthene, or Radiant, and we learned how different rates of these broadcast insecticides work for thrips management.

Bollworm resistance monitoring (Objective 4) showed that high numbers of moths survived the adult vial test, consisting of 24 hours of exposure to cypermethrin (a standard pyrethroid). The mean survival of 37.1% for the 2012 season was the highest ever recorded for Virginia since this program was initiated in 2003.

Results from four BMSB cage experiments in Virginia in 2012 (Objective 5) indicated that BMSB nymphs are piercing (or creating more warts on) larger bolls compared with smaller bolls. Extension recommendations currently consider large bolls (greater than 1.1-inch diameter) to be "safe" from native stink bug feeding. If BMSB ever becomes a common invader of cotton fields, sampling procedures, and possibly thresholds, may have to be developed specifically for this invasive species.

 

Project Year: 2012
 

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