Effect of rice sowing date on occurrence of the small brown planthopper and epidemics of the planthopper-transmitted rice stripe virus disease

Chinese. 【目的】了解水稻播种期对灰飞虱及其传播的条纹叶枯病发生流行的影响。【方法】2006～2007年2年田间设置4个播种期，调查分析水稻灰飞虱种群动态和条纹叶枯病发病的程度。【结果】播种期是影响条纹叶枯病的重要因子。在浙江北部，单季晚稻随着播种期的推迟，病情递减；秧田期株发病率与播种期的关系可以Weibull方程来描述、与秧田期灰飞虱种群动态曲线下面积（AUCPD，即累计虫日）或高峰期密度则呈Logistic关系；本田稳定期发病率则可以以播种期、秧田期灰飞虱高峰期密度、秧田末期的株发病率来描述，而本田期的AUCPD并不是描述该阶段的发病率的必要变量。【结论】在综合治理中，适期播种是控制该病害流行的最有效方法之一，在浙江北部单季粳稻移栽的适宜播种期为5月底～6月上旬。

English. [ Objective] To understand the relationship between rice sowing date and the occurrence of the rice small brown planthopper （SBPH） Laodelphax striatellus Fallen and the epidemics of the planthopper- transmitted rice stripe viral （RSV） disease. [Method] Four sowing dates of rice were set up in 2006 and 2007. [Result] The results showed that the peak density of the planthopper and the RSV incidence in both nursery and transplanted field were decreased with the postponing of the sowing date in single crop of japonica rice in north Zhejiang Province. The relationship of seedling RSV incidence at the end of the nursery to the sowing, date was well-described by a Weibull equation, while the incidence to the area under the curve of population dynamics （AUCPD, or planthopper-day accumulation） or the peak density of the planthopper in the nursery could be summarized by a Logistic equation. The RSV incidence in the transplanted fields could be characterized quantitatively by a multivariate regression equation including the variables of sowing date, peak density of the vector in and the RSV incidence at the end of the nursery. That the descriptive model excluded the AUCPD in transplanted field implies this variable is not necessary for forecasting of the disease epidemics in the field. [Conclusion] The 2-year experiments sufficiently indicated that the suitable sowing of rice could be used as one of the effective measures to control the vector population and therefore the planthopper-transmitted RSV in larger scale region. The optimal sowing date for the single-cropping transplanted Japonica rice is recommended as from late May to early June.