Analyses of time-dose-mortality model of the emulsifiable formulation of Metarhizium flavoviride Mf82 against Nilaparvata lugens
黄绿绿僵菌Mf82悬乳剂对褐飞虱作用的时间-剂量-死亡率模型分析

In order to effectively control Nilaparvata lugens, ten strains of entomogenous fungi including a new strain of Metarhizium flavoviride, Mf82, isolated from N. lugens and six strains of Beauveria bassiana and four different species of Metarhizium were bioassayed for its virulence against the adults of N. lugens. The results showed that cumulative mortality (81.7%) of strain Mf82 was the highest among all tested strains, and the median lethal time (LT50) value was 4.6d at a concentration of 1.0×108conidia/mL. Thus, an emulsifiable formulation of Mf82 was processed in the laboratory, and the bioassay of virulence of Mf82 against N. lugens was carried out. The results showed that the daily cumulative mortality of N.?lugens increased with the concentration of conidial suspension, and the highest concentration (1,048conidia/mm2) treatment caused 85.0% mortality. A time-dose-mortality model was used to analyze the bioassay data and the model fitted the data well, resulting in parameters for estimating the time and dose effects. The estimated LC50 values on day 7 and 9 post treatment were 2.1×103, 9.9×102conidia/mm2, respectively; while LC90 were 7.8×104, 3.7×104conidia/mm2, respectively. The LT50 of the emulsifiable formulation of M. flavoviride against the N. lugens differed at various logarithmic dose, and values of LT50 of tested agents were shortened with logarithmic dose. While logarithmic dose increased from 7.0 to 8.0, the LT50 values reduced from 8.9d to 5.7d. It is thus clear that the emulsifiable formulation of M. flavoviride has high virulence to N. lugens, and this new formulation could be used for biocontrol of N. lugens.