Studies were conducted to examine the micromorphology of leaf surfaces of coca and nova plants and to determine which spray diluents provided optimum coverage of leaf surfaces. Adaxial leaf surfaces of both species were covered with a smooth layer of polygonal-shaped epidermal cells which were covered with wax crystals. Abaxial leaf surfaces were composed only of papillae cells and the guard and subsidiary cells surrounding stomata. Abaxial leaf surfaces of both species were also covered with wax crystals. Average wax weights were 28 to 53 μg cm−2. Water droplets containing an organosilicone surfactant at 0.1% by vol spread better on leaf surfaces that did other adjuvants. Droplets of several different petroleum-based oils spread much better on leaf surfaces than either water droplets with adjuvants or droplets of soybean or cottonseed oil.