三种药剂对早稻二化螟的防效及施药适期探讨

试验结果表明,氯虫苯甲酰胺、氯虫·噻虫嗪有对二化螟Chilo suppressalis(Walker)有较好的防效和较长的持效,一次施药可兼治多个峰次。20%氯虫苯甲酰胺150mL/hm2、40%氯虫·噻虫嗪120g/hm2和2.15%甲氨基阿维菌素苯甲酸盐750mL/hm2在二化螟2龄幼虫高峰期施药,药后8d对幼虫防效分别达94.7%、91.2%和91.0%;药后18d的防效依次为99.0%、98.0%、73.2%,氯虫苯甲酰胺、氯虫·噻虫嗪处理防效仍高于药后8d,但甲氨基阿维菌素苯甲酸盐处理防效明显下降;药后18d对主峰保苗效果(枯心)氯虫苯甲酰胺和氯虫·噻虫嗪分别为99.0%、98.0%,甲氨基阿维菌素苯甲酸盐处理偏低,为73.2%。对后峰保苗效果(枯鞘)氯虫苯甲酰胺为84.9%好于氯虫·噻虫嗪处理的69.3%,甲氨基阿维菌素苯甲酸盐的防效仅为7.1%。氯虫·噻虫嗪不同时期施药处理后,主峰卵孵高峰后14d考查,防治效果和保苗效果以卵孵高峰施药最好,其次为2龄幼虫高峰期施药;主峰卵孵高峰后24d考查,主峰卵孵高峰至3龄幼虫高峰施药对主峰均有较好的防效,但对后峰的防效,随着施药时间推迟而提高,但在螟虫重发地区施药过迟,前期的大量枯鞘会影响稻苗生长与分蘖。因此作者建议在二化螟发生量大、后峰数量多地区,采用主峰卵孵高峰和后峰卵孵高峰2次防治对策,在螟虫发生较轻、后峰数量较少或全代发生较为集中地区,可根据当地虫情发生情况,适当推迟施药,达到一次用药,解决全代螟害。甲氨基阿维菌素苯甲酸盐持效期较短,可根据螟虫发生峰次施用。

Control effect and optimum sprayed period of chlorantraniliprole pesticide on Chilo suppressalis of early rice

The effectiveness and optimum spraying period of the three pesticides（chlorantraniliprole,chlorantraniliprole thiametho,and emamectin benzoate） were assessed with regard to the control of the striped rice borer Chilo suppressalis（Walker） on early rice in double rice-cropping seasons.The results indicate that chlorantraniliprole and chlorantraniliprole thiametho provided better and more prolonged control and a single application of these pesticides may effectively control multiple peaks of a striped rice borer epidemic.Spraying with 20% chlorantraniliprole（SC150 mL /hm2）,40% chlorantraniliprole thiametho（WDG120 g /hm2）,and 2.15% emamectin benzoate（EC750mL /hm2） reduced the main peak of the larval epidemic by 94.7%,91.2%,91.0%,respectively after 8 days,and by 99%,98%,73.2% respectively,after 18 days.Chlorantraniliprole was most effective with 84.9% efficiency during the latter peak of sheath blight,and its 69.3% borer control was better than that achieved by chlorantraniliprole thiametho.However,emamectin benzoate had control efficacy of only 7.1%.The timing of spraying affected Chlorantraniliprole＇s effectiveness;during the main peak of sheath blight,the optimum control period was at the peak of hatching followed by the 2nd stage larval peak.During the main peak of ovary blight,spraying was more effective from the peak of hatching to the 3rd larval stage.During the later sheath blight peak;an additional spray of the pesticide improved control efficiency.However,spraying too late during a massive early sheath blight epidemic resulted in depressed plant growth and reduced numbers of tillers as a result of early sheath blight.Therefore,it is recommended that chlorantraniliprole should be sprayed twice during the prominent and late peaks of egg hatching,in regions with heavy borer epidemics,but in regions with relatively light borer infestations spraying during the later peak of infestation may be sufficient.