Spray ununiformity observed in nozzle motion spraying pesticide on eggplants

A pesticide was sprayed in a field of V-shaped training eggplants (height: 2.2 m) by a grower with the conventional method such that the motion of a nozzle drew a wavy curve, and the distribution of pesticide adhesions on leaves was investigated. Also, the level of pesticide adhesion during a wavy motion (wavelength: 2 m, wave height: 1 m) of the nozzle was studied under the condition in which a pesticide was sprayed onto a side of a row of eggplants. The maximum quantity of pesticide adhered on the underside of leaves which were located on the line of spray during the upward motion of the nozzle (Location A). On leaves located on the line of spray during the downward motion (Location B), the mean quantity of pesticide was less than 10% of that on the leaves in Location A. In other locations which were located aside from the line of spray, the quantity of pesticide was below the detectable level. The maximum quantity of pesticide adhesion on the topside of leaves occurred on the leaves in Location B. There was a reasonable level of pesticide adhesion on the leaves in Location A and in Location D which was surrounded with the upward and downward line drawn by the motion of the nozzle. The minimum quantity of pesticide adhesion occurred on the leaves in Location C which was surrounded with the downward and upward line. The number of western flower thrips on the underside of leaves depended on the quantity of pesticide adhesion. Pesticide spraying to both sides of the plants did not change the above results. When the colouring solution was sprayed, it was obvious that the direct adhesion was 40 cm wide along the line of spray, but it almost didn't in the other area. These results show that spray ununiformity occurs during the upward and the downward motion of the nozzle, as well as among leaves which are located on or aside from the line of spray.