The Effect of Spray Volume and Quality on Handgun Delivery of Pesticides to Greenhouse Plants

Authors: Derksen, Richard; Frantz, Jonathan; Ranger, Christopher; Locke, James; Zhu, Heping; Krause, Charles

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 6/12/2007
Publication Date: 6/27/2007
Citation: Derksen, R.C., Frantz, J., Ranger, C.M., Locke, J.C., Zhu, H., Krause, C.R. 2007. The Effect of Spray Volume and Quality on Handgun Delivery of Pesticides to Greenhouse Plants. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE). Paper No. 071149.

Interpretive Summary: The greatest increase in greenhouse sales in the 2006 reporting period was in potted plants. Due to the cosmetic needs of ornamental crops, intensive pest management programs are required to provide the high quality products that consumers seek. Despite these requirements, little information is available to growers on how to most efficaciously apply crop protection materials. A greenhouse trial was established to determine differences in spray retention in a poinsettia canopy between applications using three different spray volumes and three different spray qualities using single nozzle handgun applicators. Measures of performance included fungicide residue on leaves and fluorescent tracer deposits on artificial targets positioned in the canopy. Results for the fungicide residue and tracer analysis were similar. For the same areas of the canopy, there were few differences in spray deposit between treatments. Fronts and upper areas of the canopy received more deposits than the backs and lower areas of the canopy. There were no significant differences in recovery of fungicide from leaves between treatments. The high volume (100 gpa) application produced the highest deposits on artificial targets across all spray qualities. There were no significant differences in overall spray deposit between the low (25 gpa) and medium (50 gpa) volume treatments. The greatest source of error may be in the operator’s ability to the plants uniformly with a single-nozzle, handgun applicator. Greenhouse producers and pest management specialists can use this information to reduce time and the carrier volume needed to make applications.

Technical Abstract: A large number of equipment options are available to producers of ornamental crops. Complicating the management decisions further is the large number of different production systems in use. Greenhouse pesticide labels lack specific recommendations on the spray volume and spray droplet sizes which will provide the most efficacious pest management. The objective of this research was to determine the effect of spray volume and spray quality on the fate of spray in a mature poinsettia canopy using handgun applications. Spray equipment was tested to determine parameters that would provide Coarse, Medium, and Very Fine spray quality. Spray volumes evaluated included 25, 50, and 100 gallons per acre over the test area. A tank mix containing a potassium bicarbonate based fungicide and fluorescent tracer were spray over the target area. Foliar samples and artificial targets were collected to assess the fate of spray in the canopy. Results for the analysis of fungicide on foliage and fluorescent tracer on artificial targets positioned in the canopy were similar. Canopy position (front/back and upper/lower), and the operator’s ability to direct spray at each target plant had more influence over deposition in the canopy than spray volume or spray quality in these trials. It was more difficult to treat the lower canopy areas and the back of plants with respect to the nozzle orientation. There was no benefit to treating with small droplet, high volume sprays as commonly used in commercial production systems. The results of this study demonstrate that application technique by the equipment operator is critical to produce a uniform application by a single-nozzle handgun.