|Krause, Charles - Chuck|
Submitted to: Journal of Pesticide Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/2/2003
Publication Date: 12/16/2003
Citation: Ebert, T.A., Derksen, R.C., Downer, R.A., Krause, C.R. 2003. Comparing Greenhouse Sprayers: The Dose-Transfer Process. Journal of Pesticide Science. 60:507-513. Interpretive Summary: A high pressure, greenhouse sprayer (DRAMM coldfogger), an electrostatic sprayer (ESS), and a low pressure, hydraulic sprayer (TXVS-6 or TXVS-18 nozzles) were tested for their ability to deliver insecticides into a dense, potted, soybean plant canopy. Their relative success was assessed by measuring deposition of a fluorescent dye on shoots and leaves, and by counting thrips or aphid abundance on shoots and leaves five days after treatment. Sprayers were evaluated using manufacturers' recommended spray volume as well as when applying the same spray volume. Overall, the low pressure sprayer produced the largest and the slowest moving droplets. In general, the DRAMM and ESS sprayers produced fairly similar droplet clouds. In three of the four tests, there were no significant differences between treatment methods in the total amount of dye retained in the canopy. The application method was not a good predictor of pest control when used according to manufacturers' recommendations. When applying the same spray volume, the sprayer type was a significant factor in predicting pest control. The smaller droplet sprays (DRAMM and ESS) resulted in numerically fewer thrips than the same volume applied with a coarse spray. Future research in this area will more fully define how this effect is achieved. Growers can benefit from this research by understanding that different forms of greenhouse sprayer technology will make toxicant application more efficient with direct benefits in reducing grower costs and reducing environmental contamination.
Technical Abstract: Innovation in spray equipment for insecticide delivery in greenhouses could improve pest control, help manage pest control costs, improve worker safety, and reduce environmental contamination. The ability of a high pressure atomizer (DRAMM), an air-assist, electrostatic sprayer (ESS), and a low pressure, hydraulic nozzle (TXVS-6 or TXVS-18) to deliver a biologically measurable dose of spinosad (Spintor 2SC) or azadirachtin (Neemix 4.5) onto greenhouse grown soybeans was evaluated based on recovery of fluorescent dye from shoots and leaves. The biological effect of the application was measured based on abundance of western flower thrips or soybean aphids at five days post treatment. Atomization characteristics of each sprayer were measured using a phase/doppler particle analyzer. The lower pressure treatments with the TXVS-18 treatment produced a spray cloud with large and generally slower moving (for 50 micron diameter) droplets relative to the DRAMM and ESS sprayers. Both application volume and the sprayer type influenced the quantity of spray retained in the canopy. Application strategy, as defined by the equipment manufacturers, did not influence pest abundance. After adjusting ANCOVA models for the dose applied, the sprayers treating at the same spray volume had an additional effect on efficacy. This was attributed to changes in toxicant distribution over plant surfaces and atomization characteristics of each machine. Understanding how sprayers influence efficacy will facilitate the development of better sprayers, facilitate development of use guidelines for application equipment and improve pesticide performance.