Laboratory evaluation of insecticides against different life stages of the tea leaf roller, Caloptilia theivora (Lepidoptera: Gracillariidae)

Abstract

The effects of 28 insecticides of 11 types on different life stages of the tea leaf roller, Caloptilia theivora (Walsingham)were investigated in our laboratory. The following life stages were examined: egg stage, early leafmining stage, late leaf-mining stage, and leaf edge rolling stage. We compared the effects of the different insecticides and examined which life stages were most sensitive to each agent. Insect growth regulators (IGR) were found to be highly effective from the egg stage to the early leaf-mining stage. Neonicotinoid was highly effective in inhibiting egg hatching. Pyrethroid•pyrethrin, avermectin, spinosyn, nereistoxin, and diamide were all highly effective against all of the life stages tested. Application of BT and some IGRs during leaf edge rolling allowed the creation of triangularshaped leaves, however, it killed the larvae in these leaves, reducing the excretion of the larval feces that is responsible for discoloration of green tea extracts. Organophosphate and METI were comparatively less effective against all of the life stages tested. These results revealed the importance of considering life stage when selecting insecticides for control of the tea leaf roller.