Effect of target wettability on spray droplet adhesion, retention, spreading and coverage: artificial collectors versus plant surfaces

This study demonstrated that natural foliage and artificial collectors range in surface wettability, affecting spray adhesion, retention, spreading and coverage. Therefore the choice of artificial collector or natural foliage depends on the scientific question. If the volume of spray available to the canopy, or spray accountancy, is to be determined then an artificial collector that will intercept and retain all of the spray is required. Careful consideration of collector is required to meet stated objectives. For example, water sensitive paper is an excellent aid to sprayer set-up, but does not distinguish differences between formulations. It also provides no indication of retention or coverage on the crop surface. All artificial collectors tested were poor indicators of adhesion and retention by, and spreading and coverage on, natural plant surfaces and should not be substituted for natural plant surfaces in field trials attempting to quantify spray retention and coverage on the crop surfaces.