Abstract:

The population dynamics of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) was monitored through methyl eugenol baited traps all year around in 1992, 1998, 2003 and 2004 in Yuanjiang dry hot valley area, Yunnan, and meanwhile, the factors including temperatures, rainfall and hostplant species were analyzed systematically in relation to the population fluctuation of the fly. The results indicated that the fruit fly occurred all year round in Yuanjiang. Its population size remained low from December to February of next year and increased steadily from March through August till it reached the peak. Afterwards, the fruit fly population declined until November. Temperatures, rainfall and host fruits were supposed to be the major factors influencing the population fluctuation. The monthly mean temperatures fell into the ranges of temperatures suitable for development and reproduction of the fly in the study area. But, the monthly mean minimum temperatures from December to February of next year appeared to be lower, and were suggested to be responsible for the low populations in this period. In contrast, the monthly mean maximum temperatures in May were too high and may have negative effect on the fly populations. Rainfall was another essential factor influencing the population fluctuations. Rainfall in summer months from June through August ranged between 100-150 mm, being helpful for the fly population increasing. Mango and orange were the most preferred hostplants for the fly. The planted areas, fruiting period and productions of the two fruit plants exerted essential effects on the fly population fluctuations in Yuanjiang valley area. Briefly, the monthly mean temperature, monthly rainfall and the host plant species, through the way of their functions, their influence strength, as well as the period that they occurred, synthetically impacted the population dynamics of the fruit fly in the study area.

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Key words: Bactrocera dorsalis, population dynamics, climatic factors, hostplants, dryhot valley, trapping