Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 16, 2007
Publication Date: December 31, 2007
Citation: Martin, D.E., Lopez, J., Hoffmann, W.C., Fritz, B.K., Lan, Y. 2007. Field evaluation of spinosad aerial applications for thrips control on cotton. Southwestern Entomologist. 32(4):221-228. Interpretive Summary: Thrips can periodically be a serious threat to seedling cotton with approximately 25% of the cotton planted in Texas requiring an application of insecticide for thrips control. Studies were conducted to optimize the aerial application of a low-mammalian toxicity compound, spinosad, using conventional, electrostatic, and rotary application systems. The product efficacy was optimized when the product was applied using conventional nozzles and was not influenced by spray rate. These studies will significantly contribute to applicators and producers being able to select the most effective control product for thrips using aerial application as the treatment method.
Technical Abstract: Spinosad (Tracer) was evaluated in a large scale field study for thrips control in early season cotton. Spinosad at 154 mL/ha was used in all treatments and compared to dicrotophos (Bidrin 8) at 292 mL/ha that was applied conventionally. Treatments were applied aerially using conventional hydraulic, electrostatic and rotary nozzle setups. Larvae and adult thrips counts were significantly less than the untreated control across all sampling dates except for larvae per plant count at 1 DAT with dicrotophos (Treatment 6) and adult numbers at 7 DAT. The greatest percent reductions of adult thrips occurred at 1 DAT when all aerial application treatments were significantly lower than the control. At 7 DAT, the three spinosad applications made with CP nozzles (Treatments 3, 4, and 5) showed the greatest control for adults and reduction of larvae. There were increases in adult numbers in the electrostatic and rotary treatments of 41% and 10%, respectively, over the control at 7 DAT. Based on spray droplet deposition data collected and thrips control obtained in this study, the optimum aerial application treatments were conventional hydraulic nozzles (CP-03) with a volume median diameter of 175 µm, at spray rates of 18.7 and 46.8 L/ha with Tracer as the active ingredient. The addition of an adjuvant did not have a significant effect on efficacy. Tracer provided equivalent or better than control of larval or adult thrips than the conventional application of dicrotophos.