Effect of partial pesticide spraying on the number of major pests and damage to new shoots of tea plants

We studied the effects of partial spraying, targeting tea [Camellia sinensis (L.) O. Kuntze] plants' plucking surfaces, on the annual number of major pests and damage to new shoots. The prevention of feeding damage to shoots caused by Empoasca onukii Matsuda (Hemiptera: Cicadellidae) was more stable when spraying at high volumes. However, the annual number of E. onukii with conventional spraying (200 L/1000 m(2)) was similar to the control (No pesticide). On the other hand, the prevention effect on shoots and the annual number of Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) in partial spraying (40 L/1000 m(2)) was similar to conventional spraying. Moreover, although high volumes of spraying (1000 L/1000 m(2)) are usually needed to control Pseudaulacaspis pentagona (Targioni-Tozetti) (Hemiptera: Diaspididae), the male adult population of P. pentagona in the control and partially sprayed field tended to be lower than that in the conventional spraying. When using pesticides harmful to P. pentagona's natural enemies, partial spraying seems beneficial. Enough pesticide spraying to widely cover the leaf layer was thought necessary to protect the tea plants' new shoots. However, the spraying method targeting only the tea plants' plucking surfaces protects the new shoots with similar efficacy. Besides, partial spraying protects pests' natural enemies, allowing additional pest population control.