Wild blueberry producers apply herbicides uniformly to control grasses and weeds without considering the significant weed density variability and bare spots within fields. The repeated and excessive use of herbicides in significant bare spots has resulted in an increased cost of production and environmental contamination. The objective of this study was to examine the impact of spot-application (SA) of herbicide using a prototype variable rate (VR) sprayer to control weeds and grasses in a wild blueberry field. The 6.1 m VR sprayer was mounted on all-terrain vehicle (ATV). The machine vision sensing and control system of the VR sprayer consisted of μEye digital color cameras mounted on a separate boom in front of the ATV, fast ruggedized computer, custom image processing software, VR controller, Land Manager II, flow valve, solenoid valves and a Pocket PC. Nine 6.1 m wide test plots were selected in a wild blueberry field and the bare spot, grass and weed areas were mapped using RTK-DGPS. Three different techniques (uniform application (UA), SA in blueberry plant areas only and SA in weed areas only) were applied in nine selected plots (each application in three randomly selected plots). Weed density was measured at 20 randomly selected data points in plant areas of each plot after approximately 2, and 10 weeks of herbicide application. Weed density data was examined to determine the impact of SA of herbicide in plant areas of the wild blueberry field as compared to a traditional UA. The chemical saved with SA in plant areas ranged from 14.17 to 31.92 % depending on the size of bare patches.