大棚草莓斜纹夜蛾的空间分布型

斜纹夜蛾Spodoptera litura(Fabricius)是大棚草莓生长初期的重要害虫。为明确斜纹夜蛾在草莓上的时空动态,连片调查了草莓上低龄幼虫数、中高龄幼虫数、受害叶片数以及叶片受害率,利用聚集度指标法、Taylor幂法则和IwaoM-m的回归法进行分析。结果表明低龄幼虫呈明显的聚集分布,中高龄幼虫则呈随机分布或均匀分布,受害叶片和受害率呈明显的聚集分布;通过聚集均数(λ)判断低龄幼虫高密度时λ>2,聚集由于成虫产卵块、初孵幼虫成聚集危害引起;低龄幼虫低密度时λ<2,聚集由植株间距等影响初孵幼虫的扩散因子引起;中高龄幼虫呈随机分布的田块的λ<2。*

Spatial distribution pattern of the common cutworm Spodoptera litura in greenhouse strawberry

The common cutworm Spodoptera litura (Fabricius)] has been one of the most destructive pests for strawberry at the early growing stage in plastic greenhouse in Hangzhou, Zhejiang province. In order to understand the spatial distribution pattern of S. litura in the strawberry field, the densities of the small larvae, the middle-large larvae, damaged leaves were exclusively sampled in the transplanted strawberry greenhouse field. Three methods of aggregated indices, Taylor’s power law and Iwao’s regression analysis of M-m were used to test the distribution patterns. The results showed that the small larvae, the number of damaged leaves and the percentage of damaged leaves belonged to the aggregated distribution, while the middle-large larvae belonged to either random distribution or even distribution. The aggregated pattern of the small larvae was caused by eggs laid by females in clumped (egg mass) and from which batches of neonates hatched.