The control efficiency of three Bt (Bacillus thuringiensis) pesticides and one Beauveria bassiana against lepidopteran pests occurring on litchi fall shoots was evaluated, with 20% of diflubenzuron diluted to 1500 times as a chemical pesticide control and water as a blank control. Our results showed that spraying of Bt B diluted at 2000 and 1500, and Bt C diluted at 1000 times exhibited higher control efficiency in comparison with other biopesticide treatments. Three days after spraying, the pest population was reduced by 77.98%, 69.45% and 59.32% by the three Bt treatments, respectively, which contrasted to the 50.58% control efficiency in the chemical pesticide control. At 7 days after spraying, the pest population was decreased by 86.87%, 78.67% and 79.58% with the three Bt treatments, which were not significantly different from that in the chemical pesticide control (91.82%). The damage indexes of the mature leaves in the three Bt treatments were much lower than that of the blank control, and percentages of damaged leaves were not different between the Bt treatments and the blank control. Compared with B. bassiana, Bt pesticides exhibited quick pest control and more stable efficiency in face of environmental stress. Based on the above results, we recommend using Bt B and Bt C instead of diflubenzuron to control lepidopteran pests of the litchi fall shoots with proper concentrations and timing.%为了明确生物农药对危害荔枝秋梢害虫的防效,采用喷雾方法测试了3种苏云金芽胞杆菌Bacillus thuringiensis(Bt)类农药和1种球孢白僵菌Beauveria bassiana在不同浓度下对鳞翅目害虫的防治效果,以20%除虫脲稀释1500倍为药剂对照,清水为空白对照.结果表明,生物农药中Bt B稀释2000倍或1500倍和Bt C稀释1000倍时的防效较好,3 d时虫口减退率分别为77.98%、69.45%、59.32%,均显著高于药剂对照组(50.58%);尽管7 d时的虫口减退率86.87%(Bt B2000)、78.67%(Bt B1500)、79.58%(Bt B1000)略低于药剂对照组的91.82%,但差异不显著.以上3种处理组老熟叶片被害指数均显著低于空白对照组,叶片危害率与空白对照组相比均未达到显著差异.相对于白僵菌处理组,Bt类生物药剂具有防效快且不易受外界环境干扰的优点.因此,建议采用Bt B和Bt C两种生物农药来替代除虫脲防治危害荔枝秋梢的鳞翅目害虫,同时要注意药剂的浓度和施药时机.
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