Since spiders are sensitive to pesticides, the use of lower-volume pesticide sprays that specifically target the plucking surface may help to preserve their assemblages. In this study, we investigated the effect of four pyrethroid pesticides on spider populations in tea (Camellia sinensis) fields when applied using a lower-volume sprayer. Abundance and composition at family level of spiders were assessed before and after treatments. We found that fewer spiders were eliminated when we used a lower-volume sprayer (40 liters/10 ares) rather than a conventional sprayer (200 liters/10 ares) due to the lower-volume treatment only covering the plucking surface (top layer) of the tea plants. These findings indicate that the tea leaf layer plays a good role in sheltering spiders during pesticide application and that the lower-volume treatment that specifically targets the plucking surface can enhance this protection. Therefore, to successfully maintain predatory spiders that prey on tea pests, tea farmers should reduce the volume of pesticides they use and try to restrict the spray to the plucking surface of the plants.

SummaryIn collaboration with Matsumotokiko Co., Ltd., we have developed a novel method for pesticide reduction using a riding-type pesticide sprayer (the "Kagoshima-style" pesticide sprayer) in tea fields that makes use of a small fog nozzle and a ventilator. This pesticide sprayer facilitates a marked reduction in the pesticide spray volume. It can also be installed in the conventional riding-type pest control machines and tractors.In the first year of examination, this novel method provided results equivalent to those of conventional methods. The influence of pesticide reduction on pest management remains to be elucidated. However, this technology presents possibilities of practical use.We would also like to advance the improvement of this method in order to correspond to tea fields in every region of the country.

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