Ecological control of Asian corn borer (ACB), Ostrina furnacalis in the sweet corn field
甜玉米地亚洲玉米螟为害的生态控制系统研究

ACB (Ostrina furnacalis) is an important pest to the sweet corn in Zhujiang Delta area. In order to reduce the serious pesticide pollution in the sweet corn field, and efficient control of ACB, the ecological control approaches through natural population life table are proposed in the paper. The studies were performed in ecological demonstration farm in Shenzhen Longgang. The experimental fields at three different densities of ACB were chosen. The host resistance variety, Trichogramma ostrininae and Steinernema feltiae A_(24) were chosen as control methods for ACB. The systematic surveys were applied and done one time every four days. The quantities of ACB and the lethal factors at different instars per each corn were recorded. According to the data from the systematic survey and the action factor life table methods, natural population life table of ACB fifth generation was built, through which, ecological control approaches for ACB were presented depending on the initial egg densities. The results show that ecological control approaches for ACB consist of artificially ecological control approach and natural control approach. The controllable factors for ACB population in artificially ecological control approach included T. ostrininae, resistance variety, S. feltiae A_(24). However, that in natural control approaches were natural enemies and some weather factors. Weather factors such as temperature and humidity are difficultly controlled, so protecting natural enemies seems to be very important. If ecological control measures were reasonably provided, the aim of ecological control should be achieved. The contents of ecological control approaches according to the different initial egg densities are as following: when the sweet corn variety is S2, the egg density of ACB are 18 lumps of egg per 100 corn plants, in this way the damage of ACB could be controlled under economic injury level (EIL) without using any control measures; and when the sweet corn variety is Y1, the egg density of ACB is 18 or 35 lumps of egg per 100 corn plants, ACB can be controlled under EIL by releasing T. ostrininae or spreading nematode granules; and when the egg density of ACB reaches at 62 lumps of egg per 100 corn plants, both T. ostrininae and nematode granules are required to the corn field in order to control ACB under EIL. The specific methods of releasing both T. ostrininae and S. feltiae A_(24) are very important. Usually, two times of releasing T. ostrininae, the quantities of which should be 375,000 wasps per hm~2, are appropriate during egg stage of ACB: one is at egg incipient stage, another is at prevailing stage. The method of spreading nematode granules is as following: spreading time is once only at corn spindle leaf stage; spreading dosage should be 10,000 pieces per plant. The ecological control approach offers a feasible no-pollution way to pest management for the ACB.