Spatial Distribution Pattern of Larva of Prodenia Litura (Fabricius) in Sweet Potato Fields

Occurrence of Prodenia litura in sweet potato fields was investigated in 2010 in order to reveal their distribution. Eight groups of samples were obtained. Several clustering indices, power law of Taylor and Iwao's way (regressive relation by m*-m) were used to test the spatial distribution pattern of P.litura in sweet potato fields. The results showed the eggs of P.litura fits the pattern of symmetrical distribution,and the larva of P.litura fits the pattern of aggregative distribution in sweet potato fields with the basic component of distribution of colony. The population density effected the Spatial distribution. The cause of their aggregation was tested by Blaekith's method, when m4.424 1,their aggregation was caused by some environmental factors such as climate,soil humidity,and growth and so on;when m4.424 1,their aggregation was caused by their behavior and environmental conditions.Based on the data of the spatial distribution, the model for determining the optimum theoretical sampling number model and the optimum sequential sampling model were proposed.