Coryneum beijerinckii conidia germinated equally well on both surfaces of almond leaves. The underside of leaves was more prone to infection than the upper side and deposits on both surfaces were required for effective disease control. Helicopter spray applications with captan gave excellent disease control, provided the spray droplet size and air speed were reduced from those normally used in commercial helicopter spray applications. The finer spray droplets and slower helicopter speed resulted in considerably more captan deposit on both surfaces of leaves and glass slides. The amount of this deposit was determined by chemical analyses and its fungitoxicity was determined by bioassay with conidia of C. beijerinckii.