[Efficacy of emulsifiable formulations of two entomopathogenic fungi against small green leafhoppers on tea plant].

A field trial was conducted to test the efficacy of emulsifiable formulations of Beauveria bassiana (Bb) and Paecilomyces fumosoroseus (Pf) conidia in controlling small green leafhoppers (Empoasca spp.) on tea plant in a hillside tea garden located in Shuichang, Zhejiang during mid-summer 2002. Both Bb and Pf formulations contained 10(10) conidia x ml(-1). Adding 3% of imidacloprid 10% WP to each fungal formulation (W/V) resulted in two other formulations, i.e., Bb-imidacloprid mixture (BbIM) and Pf-imidacloprid mixture (PfIM). Besides the four formulations, a mineral oil-based liquid used to formulate the fungal conidia and containing 3% of imidacloprid 10% WP (OBLI) was also tested, and water spray was used as control (CK). Each of the treatments included three 60-m2 plots (replicates), which were sprayed twice with a 500-fold aqueous dilution of the corresponding formulation or preparation at a 12-d interval. Based on the leafhopper densities estimated by sampling in all plots at 3- or 4-d intervals after the first spray, the spray of BbIM or PfIM could better control the leafhoppers than the spray of Bb or Pf formulation. The maximal efficacy relative to CK reached 83.4% and 71.3% in the BbIM and PfIM treatments, respectively. Estimates of field efficacy obtained during the 25-d period after the first spray was 66.8% for BbIM, 62.1% for PfIM, 50.3% for OBLI, 49.5% for Bb, and 19.0% for Pf, respectively. A discussion was also given on the effect of local weather pattern and leafhopper population age structure on the results of the field trial, and on the application techniques to enhance the efficacy of mycoinsecticides against Empoasca species on tea plant.