COPPE, Chemical Engineering Program, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
Embrapa Meio Ambiente, Jaguariúna, Brazil.
Pest Manag Sci. 2019 Nov;75(11):2882-2891. doi: 10.1002/ps.5458. Epub 2019 Jun 4.
Microbial surfactants are multifunctional surface-active molecules that have been overlooked in formulating microbial biopesticides. We report a novel approach using the biosurfactant rhamnolipid (RML) against the destructive cosmopolitan insect pest Bemisia tabaci, as well as the combined action of RML with aerial conidia of two entomopathogenic fungi, Cordyceps javanica and Beauveria bassiana. RML was also tested as a suspension agent to improve the recovery rate of conidia from solid substrate for fungal preparations.
The recovery rate of conidia increased dramatically (two to five times) with RML compared with a standard surfactant (Tween 80). Spraying solutions of 0.075% and 0.1% (w/v) RML on B. tabaci third instar nymphs induced 100% mortality within 4 days. Conidial suspensions at 5 × 10 conidia/mL amended with RML at 0.01% or 0.05% markedly increased nymphal mortalities and considerably reduced LC . Conidial suspensions of B. bassiana with 0.05% RML added were more effective against whitefly nymphs (87.3% mortality) than C. javanica + RML (51.4% mortality).
Our results show that this bacterium-based RML improved the recovery rate of hydrophobic conidia, and that mixtures of RML with fungal spore suspensions increased their insecticidal activity. © 2019 Society of Chemical Industry.
微生物表面活性剂是多功能的表面活性分子，在微生物生物农药的配方中被忽视了。我们报告了一种使用生物表面活性剂鼠李糖脂（RML）来防治破坏性世界性害虫烟粉虱的新方法，以及 RML 与两种昆虫病原真菌虫草和球孢白僵菌的气生孢子的联合作用。还测试了 RML 作为悬浮剂来提高真菌制剂固体基质中孢子的回收率。
与标准表面活性剂（吐温 80）相比，RML 使孢子的回收率显著提高（提高了两倍至五倍）。在 B. tabaci 三龄若虫上喷洒 0.075%和 0.1%（w/v）的 RML 溶液，在 4 天内可引起 100%的死亡率。用 0.01%或 0.05%的 RML 改良的 5×10 个孢子/mL 的孢子悬浮液，显著增加了若虫的死亡率，并大大降低了 LC。添加 0.05%RML 的 B. bassiana 孢子悬浮液对粉虱若虫（87.3%死亡率）的效果优于 C. javanica+RML（51.4%死亡率）。
我们的结果表明，这种基于细菌的 RML 提高了疏水性孢子的回收率，并且 RML 与真菌孢子悬浮液的混合物增加了它们的杀虫活性。© 2019 化学工业协会。
