FIELD TRIALS OF A BEAUVERIA BASSIANA FORMULATION AGAINST APHIDS AND ITS SHELF-LIFE AT AMBIENT TEMPERATURE
白僵菌孢子悬乳剂田间控蚜效果与常温货架寿命测定

An emulsifiable formulation of Beauveria bassiana conidia (Bb), prepared with an oil-based liquid containing stabilizer and UV protectant and standardized as 1010 conidia/ml, was tested alone or together with 3% of imidacloprid 10%WP (Bb Im) for efficacy against Myzus persicae on Chinese cabbage in Yuyao, Zhejiang during May 2003. After spraying 1000-fold dilutions twice in two fields at 10-day interval, relative efficacies reached up to 94.5% and 86.2% for the Bb Im, 86.4% and 73.1% for the Bb, but only about 50% when imidacloprid was applied at the low rate added to the Bb Im. In extensive field trials for control of various aphids on cowpea, cabbage, Chinese cabbage, turnip and pear trees during the summer, relative efficacies against vegetable aphids ranged from 48% to 68% within 5-10 days after one spray of 1000-fold dilution of the mixed formulation Bb Im. Particularly, the mixed formulation resulted in a 99% control of Schizaphis piricola population on pear trees. During an 18-month period of storage at ambient temperature in dark, the oil-based B. bassiana formulations with or without the additives were very stable with conidial viabilities fluctuating around 95% during the first 7 months and remaining about 75% by the end of 10 months. Thereafter, however, the viability of the conidia in the formulation containing the additives decreased rapidly and was not detected by the end of 16 months. In contrast, the formulation not containing the additives had conidial viabilities of 57%, 51%, and 42% on months 16, 17, and 18, respectively.