Abstract: Annual monitoring was conducted on the population dynamics of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) through methyl eugenol-baited traps in Liuku, Yunnan from 2003 to 2005 respectively. Temperature, rainfall and host-plant species were analyzed in relation to population fluctuation of the fly. The results indicated that during the study periods, adults of the fruit fly occurred seasonally from March to December. The population fluctuation was single peaked, with the peak in July. There were close relationships between the fluctuation of B. dorsalis male adult abundance and such environmental factors as temperature, rainfall, and raining days in Liuku, Yunnan. Decision coefficient and path analyses indicated that the monthly rainfall was the major decision factor, and the monthly mean temperature and the monthly mean minimum temperature were the crucial limiting factors, of which the monthly mean minimum temperature was the most important factor indirectly negatively influencing population increasing. The principal component analysis screened out the first principal components, all representing the low temperature condition, whose cumulative variance proportion was 77.65%. The results of stepwise regression analysis also indicated that the monthly mean temperature and the monthly mean minimum temperature were the major climatic factors influencing the population fluctuation. In conclusion, the lower temperature condition was the key factor resulting in the seasonal population fluctuation of B. dorsalis in Liuku, Yunnan.

Key words: Bactrocera dorsalis, population dynamics, climatic factors, host plant, methyl eugenol, Yunnan