IMPROVING CROP PROTECTION TECHNOLOGY FOR HORTICULTURE CROPS
Location: Application Technology Research Unit
Title: Comparing Greenhouse Sprayers: The Dose Transfer Process
Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 6, 2003
Publication Date: July 27, 2003
Citation: Ebert, T.A., Derksen, R.C., Downer, R.A., Krause, C.R. 2003. Comparing Greenhouse Sprayers: The Dose Transfer Process. Pest Management Science. 60(5):507-513.
Interpretive Summary: A high pressure, greenhouse sprayer (DRAMM coldfogger), an electrostatic sprayer (ESS), and a low pressure, hydraulic sprayer were tested for their ability to deliver insecticides onto chrysanthemums or poinsettias for control of aphids or whitefly. Each sprayer was used to treat the plants at three different spray volumes; each volume representing the recommended application volume for each piece of equipment. Total spray volume was changed only by varying the total time spent delivering the material to the target canopy. Pesticide efficacy was evaluated five days post-treatment. Across all three spray volumes, the low pressure, hydraulic sprayer produced higher spray deposits on target canopies than the other two sprayers. Independent of sprayer type, lower spray volumes produced greater spray retention on target canopies. However, higher rates of spray retention did not necessarily correlate with greater pest control. Plants treated with lower spray volumes had more pests five days post-treatment. These results indicate that the two sprayers designed to make lower volume applications, the DRAMM and ESS, improve the bioavailability of pesticide and thus increase chances of successful pest management under the conditions evaluated in this study. However, these results also indicate that the spray volumes applied with these two sprayers could be optimized further to provide greater bioavailability of pesticide. Growers can benefit from this research by understanding that the success of a particular pest management strategy depends on many factors. This knowledge will help select spray equipment best suited for their pest management needs.
The efficacy of a particular pest management strategy is a function of the manner in which pest management materials are delivered. Delivery is a function of many variables including but not limited to the travel speed, flow rate of liquid through a nozzle, the number of nozzles, the type of nozzle and physical properties of the spray formulation. Changing one variable could affect other aspects of the application as well. This study was designed to limit the number of changes in variables that could impact the efficacy of an application. Three machines, a conventional, lower pressure, high volume sprayer, an air-assist, electrostatic sprayer and a high pressure, low volume sprayer were used to apply dilute insecticide applications to control aphids on chrysanthemums or whitefly on poinsettias. Treatments made with the low pressure, hydraulic sprayer, resulted in higher retention of spray material on leaves; however, these plants also had more pests. Plants treated at low application volumes, independent of sprayer type, retained more spray than plants treated at higher spray volumes. In general, low volume treatments resulted in more pests on plants. It is clear there is not necessarily a correlation between overall spray retention and efficacy. It emphasizes the importance of understanding the effect of spray or toxicant distribution on the target. These results demonstrate the importance of separating application variables such as spray or carrier volume from changes in spray equipment. Understanding the importance of affect of individual variables on application efficacy will facilitate future evaluation of pest management strategies.