瓢虫种群对棉花-玉米农田景观格局的响应

Effects of farmland landscape patterns on the population dynamics of two lady beetles

本文研究了华北棉花-玉米农田景观格局中龟纹瓢虫Propylaea japonica(Thunberg)和异色瓢虫Harmonia axyridis(Pallas)种群动态,发现农田景观格局中作物类型(棉花与玉米)对两种瓢虫种群密度动态有显著的影响,两种天敌瓢虫都趋向在玉米斑块上栖息。两种瓢虫在棉花斑块上呈现出时间分化,其中龟纹瓢虫在棉花种植的前中期种群密度较大,后期较少;而异色瓢虫在棉花前中期种群密度较少,后期较多,表明农田景观中种植玉米有利于增强瓢虫对棉花害虫的控制作用。进一步的研究表明,农田景观系统中玉米斑块所占的面积比对龟纹瓢虫和异色瓢虫种群密度均产生显著影响。这说明在农田景观系统中开展区域性生态调控的时候,需要考虑到各类斑块组合的面积比例,从而有利于增强多种天敌昆虫的协调控害作用。

Population dynamics of two predatory beetles, Propylaea japonica （Thunberg） and Harmonia axyridis （Pallas） were surveyed in agricultural landscapes composed of cotton and maize in North China. Crop composition （cotton and maize） was found to significantly affect population densities of the beetles in this agricultural landscape system. Population densities of both beetles in maize patches were higher than in cotton patches, and adults of both species prefer to inhabit maize plants. The population densities of the two species varied through time in the cotton patches, with more adults of P. japonica in the earlier and middle stages and fewer in the later stage, and fewer adults of H. axyridis in the earlier and middle stages and more in the later stage. These results suggest that maize can serve as a habitat or refuge for predatory beetles and its presence may enhance biological control of insect pests in cotton. The proportion of maize patches in the agricultural landscape significantly affected adult densities of these two predatory beetles. This suggests that habitat management with a suitable ratio and spatial arrangement of cotton and maize may enhance the biological control of pest insects.