Visual and image system measurement of spray deposits using water-sensitive paper

Water-sensitive papers (WSP) were attached to leaves in nursery trees and sprayed with air-blast sprayers. Deposit patterns on the WSP were rated visually for coverage, from 0 (no spots) to 10 (completely blue). Visual counts of spot density (spots/cm(2)) were made for cards representing coverage ratings from 1 to 6. WSPs were analyzed with an imaging system; several spot size parameters, number of spots, and area coverage percentage were measured. Visual ratings of 6, 7, and 8 had considerable variability in area coverage percentage. Sample WSPs with visual coverage ratings of 3, 5, 6, and 8 and minimum, median, and maximum coverage percentages are presented. Visually measured spot density was greater than image-system measured spot density for all rating numbers, especially for higher spot densities. Spot density began to decrease at visual rating numbers greater than 7.