Performance Evaluation of a Prototype Variable Rate Sprayer for Spot - Specific Application of Bravo® Fungicide in Wild Blueberry

Abstract

Wild blueberry yields are highly dependent on fungicides to control floral blight (monilinia and botrytis) and leaf diseases (septoria and rust). Growers apply fungicides uniformly without considering the significant bare spots (30-50% of the total field area). The repeated and excessive use of agrochemicals in bare spots has resulted in an increased cost of production. The over use of the fungicides is harmful to the environment and can contaminate surface and ground water. The proper targeting of fungicide on only foliage has the potential to save a substantial amount of chemical. Therefore, a significant need of an affordable variable rate sprayer for spot application of fungicide is needed for wild blueberry production. The objective of this study was to determine the performance of a prototype variable rate sprayer for spot application of Bravo fungicide in wild blueberry fields. The 6.1 meter VR sprayer was mounted on a all-terrain vehicle. Color cameras were used to detect bare soil areas in wild blueberry fields. Eighteen 6.1 meter wide test plots were selected in a wild blueberry field and the bare soil areas were mapped using RTK-DGPS. Three application rates (uniform, variable and control) were selected at random for each plot. Digital color images were taken at 6 randomly selected locations in each of the 18 plots. Each image was analyzed to calculate green ratio for determining effect of Bravo on wild blueberries. The application tracks were statistically compared with reference to the control tracks. Water sensitive paper was also placed in randomly selected locations for analysis purposes. The results can be used to determine the performance of applying fungicide on site-specific bases using a variable rate sprayer.