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

为了寻找褐飞虱Nilaparvata lugens生物防治的新途径,用新分离出的黄绿绿僵菌Metarhiziumflavoviride(Mf82)菌株与实验室保存的黄绿绿僵菌、金龟子绿僵菌和球孢白僵菌3种菌种9个菌株作对比,测定了它们对褐飞虱成虫的毒力。结果表明:Mf82菌株对褐飞虱成虫的毒力最高,以1.0×108个孢子/mL的孢子液喷雾接种到褐飞虱成虫体表上,累积死亡率高达81.7%,LT50为4.6d,致病效果显著高于其他受测菌株。在此基础上研制了黄绿绿僵菌悬乳剂,并研究了其对褐飞虱的致病力。结果表明:随着黄绿绿僵菌浓度的增加,褐飞虱的累计死亡率增加,在浓度为1,048个孢子/mm2时,累计死亡率达到85.0%。利用时间-剂量-死亡率模型对数据进行处理,所建模型均顺利通过Hosmer-Lemeshow拟合异质性检验,表明模型拟合良好,并由模型估计出了该剂型对褐飞虱的致死剂量与致死时间。在接种后第7天和第9天,LC50值分别为2.1×103、9.9×102个孢子/mm2,LC90分别为7.8×104、3.7×104个孢子/mm2。黄绿绿僵菌悬乳剂对褐飞虱的致死时间与对数剂量相关,供试菌剂LT50值随着对数剂量的增加而递减,对数剂量由7.0增加到8.0时,LT50由8.9d降为5.7d。可见该黄绿绿僵菌悬乳剂对褐飞虱具有较强的毒力,在褐飞虱生物防治中具有广阔的应用前景。

Analyses of time-dose-mortality model of the emulsifiable formulation of Metarhizium flavoviride Mf82 against Nilaparvata lugens

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.