宿主虫龄对斜纹夜蛾核型多角体病毒病流行的影响

通过对田间感病幼虫跟踪观察，研究了对斜纹夜蛾不同龄期幼虫喷施斜纹夜蛾核型多角体病毒后，病毒病在当代种群中的田间流行动态．结果表明，随虫龄的增大，幼虫对病毒的敏感性下降，宿主幼虫病死率降低，病死速率减慢，病死持续时间延长，幼虫病亡和疾病现患始期、高峰期推迟．对不同龄期幼虫喷施病毒后，幼虫每日病死时间分布可用互补重对数模型较好地拟合(Hosmer-Lemoshow统计量检验不显著)，模型中各项系数经t检验达极显著水平；疾病现息时间分布可用Holliday模型拟合，模型经F检验显著，方程中各项系数达到或接近显著水平；幼虫逐日病死时间分布可用’Weibull模型、Gompertz模型及Lo—gistic模型较好地拟合，通过用剩余平方和Q比较各模型的拟合程度，表明Gompertz模型拟合效果最好．

Influence of host age on the epizootic of nuclear polyhedrosis virus of Spodoptera litura

Through investigation of tracking infected Spodoptera litura larvae, a study was carried out to observe the epizootic dynamics of nuclear virus disease of S. litura after virus release in different instar with concentration of 2.15 x 10(7) PIBs.ml-1 in vegetable field. The results showed that with the age of S. litura increasing, the susceptibility to virus, mortality and death velocity decreased, the disease death sustained period of larvae obviously elongated, and the time that larval mortality and diseased prevalence began and peaked were postponed. The distribution of disease death time could be well simulated by Complementary log-log model (CLL). Hosmer-Lemoshow test showed that the theoretic values well fitted to observed data, and t-test indicated that the coefficients of the model reached significant level. The distribution of diseased prevalence of host larvae was simulated by Holliday model, the regression of function was significant by F-test, and its coefficients reached or approached significant level. Moreover, the cumulative diseased death time distribution could be described by S-type models (Gompertz, Logistic, Weibull), in which, the Gompertz model was the best.