VISUAL AND IMAGE SYSTEM MEASUREMENT OF SPRAY DEPOSITS USING WATER–SENSITIVE PAPER

ABSTRACT. 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/cm2) 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