Field efficacy of emulsifiable suspensions of Beauveria bassiana conidia for control of Myzus persicae population on cabbage

The conidial powder of Beauveria bassiana SG8702 produced using a diphasic fermentation technology was formulated into emulsifiable suspension I (EI-I, > 10(10) conidia.ml-1) and ES-II, which resulted from adding 1% (W/V) of imidacloprid 10% WP to the ES-I. Three dilutions (10(7), 10(6), and 10(5) conidia.ml-1 of each were sprayed onto cabbage plants for control of the green peach aphid Myzus persicae population in field plots in Kunming, Yunnan during July 2001. Each dilution and a water spray as control were replicated three times. During a 28 d period of sampling at 3 or 4 d intervals, spray of the ES-II at 10(7) conidia.ml-1 controlled the increase of the aphid population by > 90% consistently from day 7 after spray. The efficacy for the ES-I at the same concentration reached 85% on day 7 after spray, exceeded 70% in the following two weeks, but declined to 64.4% on day 24 and 52.6% on day 28. At the lower concentrations sprayed, both suspensions significantly suppressed the increase of M. persicae popula