Research on the Spatial Distribution Pattern and Sampling Technique of Noorda blitealis Walk Larva

Purpose Noorda blitealis Walk (Lepidotera: Crambidae), a pest newly discovered on moringa trees in China, whose larvae feed on leaves and fruits. In order to understand the distribution of their larvae at moringa plantation, an investigation with stratified random sampling was conducted on the larvae number in moringa plantation of Yuanjiang County, Yunnan Province in September, 2015.

Method Six aggregation indices (C、I、C_a、m^*/m、L_a、K) and two regression models (Iwao’s regression equation and Taylor’s power law) were used to test and determine the spatial distribution patterns of N. blitealis larvae of moringa plantation, the reasons for the aggregation of N. blitealis larvae was analyzed according to estimation by aggregation mean (λ).

Result The spatial distribution pattern of the larvae belonged to the aggregation distribution with density dependence. Basic component of spatial distribution was a group of individuals, which attracted one another. In addition, the aggregation average method was applied to analyze the aggregation reasons of the larvae. The oviposition and feeding habit of N. blitealis and environmental factors were the main factors. The average population density of larvae was less affected by horizontal direction, but greater affected by vertical direction. The optimal sampling equation N=t²/D²(3.548/m+0.253) and sequential sampling equation T\rm(n\rm) = n \pm \rm1\rm.95\sqrt n were established.

Conclusion This study enriches the data of N. blitealis in Yunnan Province and provides the base for forecast and control of N. blitealis.