草地贪夜蛾的防治时期和次数对玉米产量的影响

草地贪夜蛾（Spodoptera frugiperda）是世界重要的迁飞害虫,具有迁飞速度快、适生区域广、繁殖能力强、危害程度高、防控难度大等特点。为了明确草地贪夜蛾的防治时期和次数对玉米产量的影响,进一步探究周年繁殖区草地贪夜蛾的防治指标提供理论依据,田间选用甲氨基阿维菌素苯甲酸盐分别于苗期、小喇叭口期、大喇叭口期和抽雄期防治草地贪夜蛾,玉米收获期测定主要产量指标,分析防治时期、防治次数、施药间隔周期与防治效果、产量增幅之间的关系。结果表明：各时期防治处理对草地贪夜蛾防效的影响程度均呈随防治时期推后而降低趋势,其中苗期防效（大于90%）优于喇叭口期,抽雄期后防效下降不到83%,施药2次后的防效均超过89%,各处理间差异不显著,施药3次后的防效均超过95%,在苗期、小喇叭口期、大喇叭口期和抽雄期4次施药后防效最高,达97.27%;玉米产量随施药次数增加而显著上升,施药4次、施药3次和苗期+喇叭口期施药2次处理的玉米产量最高（均超过10 t/hm²）,这3种处理的玉米产量分别为10.96、10.59、10.14 t/hm²,显著高于其他施药2次和施药1次的处理;苗期施药（7.29 t/hm²）、小喇叭口期（8.04 t/hm²）、大喇叭口期（7.56 t/hm²）及小喇叭口期+抽雄期（9.08 t/hm²）的产量差异不显著,均高于抽雄期（5.85 t/hm²）的产量,表明抽雄期后施药增产效果不明显,所有施药处理产量均显著高于对照（4.29 t/hm²）;施药次数、间隔周期与玉米产量增幅之间呈二次函数关系,间隔15~20 d施药玉米产量增加幅度最大,施药次数在2~4次产量增幅最高,均出现产量增幅超过60%的处理,产量增幅最高达63.43%（施药3次）,施药次数在3~4次产量增幅并不明显。海南甜玉米种植区草地贪夜蛾化学防治,建议选择苗期、小喇叭口期、大喇叭口期施药2~3次能达到高产高效的目标。

Effects on Control Period and Frequency of Spodoptera frugiperda on Corn Yield

Spodoptera frugiperda (J. E. Smith) is an important migratory pest in the world. It has the characteristics of fast migratory speed, wide suitable area, strong reproduction ability, high degree of damage, and difficulty in prevention and control. In order to clarify the relationship between the control period and frequency of S. frugiperda and corn yield in the annual breeding area, emamectin benzoate was used to control S. frugiperda at seedling stage, small bell mouth stage, big bell mouth stage and tasseling stage respectively under field conditions. The main yield indexes were recorded at harvest stage, and the relationship between control period, control frequency, application interval and control effect and increase of yield was analyzed. The results showed that the effect of control treatments on the control effect of night was decreased with the delay of the control period, and the control effect at seedling stage (more than 90%) was better than that at bell mouth stage. The control effect decreased less than 83% after tasseling stage. The control effect after 2 times of application is more than 89%, and the difference between the treatments is not significant; the control effect after 3 times of application is all over 95%. In the seedling stage, small bell mouth stage, big bell mouth stage and tasseling stage, the control effect was the highest after 4 times of application, reaching 97.27%. The corn yield increased significantly with the increase of application times, and the highest corn yields were treated with 4 times of application, 3 times of application and 2 times of application at seedling + bell stage (both more than 10 t/hm²). The yields of 4 times, 3 times and 2 times at seedling + small bell stage of application were the highest, which were 10.96 t/hm², 10.59 t/hm² and 10.14 t/hm², respectively, which were significantly higher than other treatments. The yield of seedling stage (7.29 t/hm²), small bell stage (8.04 t/hm²), big bell stage (7.56 t/hm²) and small bell + tasseling stage (9.08 t/hm²) was not significant, and they were all higher than tasseling stage (5.85 t/hm²). It indicated that the effect of pesticide application after the tasseling period was not obvious. The yield of all pesticide treatments was significantly higher than that of CK (4.29 t/hm²). Meanwhile, there was a quadratic function relationship between the number of application times, the interval period and the increase in corn yield. The largest increase in maize yield was observed by applying pesticides at intervals of 15-20 d. The highest yield increase was between 2 times and 4 times of application, and the treatments with the output increase more than 60% appeared. The highest yield increase was 63.43% (3 times of application), and the increasing value of yield was not obvious between 3 times and 4 times. Chemical control of S. frugiperda in the sweet corn of Hainan, the goal of high yield and high efficiency can be achieved by applying 2-3 times in the seedling stage, small bell mouth stage and big bell mouth stage.