| The entomopathogenic fungus, Beauveria bassiana, is a classic fungal biocontrol agent and has been developed into a series of commercial formulations, called mycoinsecticides, for control of insect pests on crops and in forest worldwide. Intensive studies on various aspects of the fungus have been undertaken in China for several decades and recent effort has been directed toward developing mycoinsecticides for practical use in production of safe agroproducts because Hypomycetes-based mycoinsecticides meet requirements for technical revolution in insect control. Based on previous studies on various aspects of the aphid-derived isolate B. bassiana SG8702 in our laboratory, the present study was conducted to establish a novel bioassay protocol in accordance with international standards and, with the protocol, to evaluate the lethal effect of unformulated conidia and emulsifiable formulation of the fungal isolate on the green peach aphid Myzus persicae. Emphasis was placed upon the quantitative interaction of the fungal formulation with imidacloprid at low sublethal concentrations. We hope that our results and the standard valuation system will help to facilitate the development and application of B. bassiana-based mycoinsecticides for aphid control.Enhanced aphidicidal activity of emulsifiable formulation of B. bassiana conidia based on a novel bioassay protocol. An emulsifiable formulation (EF) of B. bassiana SG8702 containing 1010 conidia/mL was prepared by suspending dry conidia in mineral oil-based liquid containing emulsifier, stabilizer and UV protectant (emulsion), and then bioassayed on newly emerged M. percisae adults in parallel to unformulated conidia (UC) of the same fungal isolate. For inoculation, five gradient concentrations of aqueous EF andUC suspensions (5 10 -1 10 conidia/mL) were separately sprayed on to aphids on detached cabbage leaves (30-40 adults/leaf) using a Micro Ulva hand-held sprayer, generating the EF concentrations of 1.5, 6.3, 32.6, 87.6 and 701.1 conidia/mm2 and the UC concentrations of 2.8, 9.2, 52.7, 114.8 and 1005.9 conidia/mm2, respectively. All concentration treatments including blank controls for EF (100-fold aqueous dilution of theemulsion) and UC (water spray only) were replicated three times (aphid colonies on three leaves), and maintained in Petri dishes at 23 and 12:12 (L: D) and examined daily for 8 days. The resulting data all fit very well to time-concentration-mortality model with the concentration effect being larger in EF (1.05+0.10) than in UC (0.8210.11). The time effect was also faster in EF than in UC. The estimates of the concentration- and time-effect parameters from the modeling were then used to compute lethal concentrations (LC50) and time (LT50). The estimates of LC50 with 95% confidence intervals for both EF and UC were 9.0 (6.9-11.6) and 634 (263-1532) conidia/mm2 on day 4 after spray, and 3.3 (2.4-4.6) and5.3 (3.2-8.6) on day 7, apparently decreasing with the increasing time lengths after spray. The estimates of LTso for EF and UC were 4.9 and 7.2 days at 5 conidia/mm2, 4.0 and 5.6days at 10 conidia/mm , and 3.2 and 4.5 days at 100 conidia/mm , apparently tending to decrease with larger counts of conidia attached to aphids on the detached leaves. The results indicate that the emulsifiable formulation of B. bassiana conidia was more aphidicidal than the unformulated conidia.Time-concentration-mortality modeling for the responses of M. persicae to imidacloprid at Ion sublethal concentrations. The response of M persicae adults to low sublethal concentrations of imidacloprid (0.01-1.0 jig/mL) sprayed by an electronic sprayer was assessed at the regime of 23癈 and 12:12 (L: D) during a 7-day period. The resultant data were fitted to time-concentration-mortality model, generating the estimates of lethal concentrations (LCs) and lethal times (LTs) that depended on each other at an expected efficacy level. On days 1 and 5 after spray, for instance, the LC50 with 95% confidential limits were estimated as 2.8 (1.8-4.6) and 0.5 (0.4-0.6) g/mL, LC70 4.3...
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