A systems analysis approach to brown planthopper control on rice in Zhejiang Province, China. II. Investigation of control strategies.
Abstract
A simulation model of the population dynamics of the delphacid Nilaparvata lugens on rice in Zhejiang Province, China, described by J.A. Cheng and J. Holt (1990), was used to assess the performance of different insecticidal control strategies. Since field trials indicated that the loss in rice yield associated with attack by N. lugens was linearly related to the peak density of the 2nd generation, control strategies were assessed in terms of the ability to minimize this peak density. Where a single insecticide treatment was given, the best time at which to apply it was at 30 days after transplanting (DAT). This was true for a range of insecticides, transplanting times, temperatures and immigration patterns. Where 2 insecticide treatments were used, treating at 30 DAT remained a robust strategy and allowed considerable flexibility in the timing of the 2nd spray while still achieving an acceptable performance. The main problem concerning control of N. lugens in Zhejiang is to decide whether insecticide treatment should be applied and, if so, whether 1, 2 or more treatments should be given. Thresholds at which treatment is required to prevent the pest from causing 5% yield loss were determined for single and 2-treatment strategies. These thresholds were found to be particularly sensitive to transplanting time and to September temperatures.