Biology and Control of the Citrus Leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) in Japan
Recent advances in research on the life history, natural enemies, sex attractant, and practical control of the citrus lceafminer (CLM) in Japan are described, Adult CLM overwinters within canopies of the citrus trees in the warmer districts of the citrus belt where the overwintering females begin to oviposit in mid-March. The moth passes 9 to 10 and 5 generations per year in the southwestern and northeastern parts of the citrus belt, respectively. Developmental zero and effective heat units for development from egg to adult emergence are 12.1°C and 206 degree-days, respectively. Eighty per cent or more larvae were killed by parasitoids and unknown factors before pupation during the summer-autumn seasons. Dominant parasitoids are Sympiesis striatipes in mainland-Japan and Cirrospilus ingenuus and Citrostichus phyllocnistoides in the Southwestern Islands. Biological control of CLM by native parasitoids is not sufficiently effective in Japan because Ageniaspis citricola, a most effective biological control agent in tropical Asia, has not been detected in Japan. A sex attractant, (Z, Z)-7, 11-hexadecadienal showed a high activity for male moths in Japan, but was ineffective for those in foreign countries. The sex attrac tant appeared to be useful for the forecasting of seasonal occurrence, and control measures by using this substance should be initiated. Insecticides are commonly used for the control of CLM on young trees. Nicotine sulfate, IGRs, imidacloprid, alanycarb and pyrethroids are sprayed 4 to 5 times at 5- to 10-day intervals during the flush developing period. Recently, CLM has become resistant to pyrethroids in some districts of Kyushu. To avoid the spread of insecticide resistance of CLM, an attempt was made to use the effective parasitoid, A. citricola, through introduction from Taiwan and Thailand to Japan.