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Abstract:The effects of 28 insecticides of 11 types on different life stages of the tea leaf roller, Caloptilia theivoraWalsingham 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.

Abstract:We conducted a laboratory investigation on the growth, copulation and egg-laying behavior of the tea leafroller Caloptilia theivora Walsingham , a serious pest of tea plants in Japan. The aim of the study was to obtain basic information that can be used to control the tea leafroller. When reared at 24 C, adult males emerged earlier than adult females by 1.5 days. On the day of emergence, adult females copulated, but males did not. These observations suggest that males have adopted a mating strategy in which they emerge earlier than females and become sexually mature before females emerge. Next, we investigated the influence of copulation frequency on the adult longevity and number of eggs laid by females. Males and females kept virgin for their entire life lived significantly longer than those allowed to mate. Males and females copulated repeatedly during their entire life when allowed to mate freely; females exposed to males for life laid more eggs than those exposed to a male for one day. Females laid eggs between 22:00 and 24:00. These findings may be used to develop a management strategy against the tea leafroller using mating disruption with synthetic sex pheromones and disturbance of oviposition by lighting.

Reduction of control effects by diamide insecticides against eggs and young larvae of the tea leaf roller, Caloptilia theivora (Lepidoptera: Gracillariidae), one of the major pests of tea, was confirmed by field and laboratory tests throughout the tea fields in Minamikyushu, Kagoshima Prefecture, Japan. In the field, chlorantraniliprole, cyantraniliprole and ginotefran were less effective than spinetram and methoxyphenozide, while the latter two showed 95 % or more control effect. In the laboratory, larval mortality by flubendiamide was between 6.9 % and 23.3 % to the Minamikyushu population while 100 % in the other population. Chlorantraniliprole and cyantraniliprole showed similar tendency but the mortality was 26.7 %-70.0 % and 60.4 %-100 %, respectively, depending on the larval stage of treatment. LC 50 -value of chlorantraniliprole determined in 2018 was drastically increased from the values determined in 2013. The reasons for development of resistance are discussed.