Insecticidal activity of essential oils in controlling fall armyworm, Spodoptera frugiperda

ABSTRACT: Fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) is one of the main pests in maize crop with developing resistance to chemical products and Bt technology. Therefore, alternative control methods such as essential oils are important steps in the implementation management strategies for this pest. This study aimed to evaluate the efficiency of essential oils (EOs) of Corymbia citriodora, Myrciaria dubia (Myrtaceae), Lippia microphylla (Verbenaceae) and Piper umbelattum (Piperaceae) in controlling S. frugiperda. The OEs were extracted and mortality tests were conducted with topic and volatile applications, in 30 second-instar caterpillars originated from insect rearing and artificial diet. As a control, we conducted tests with distilled water and acetone. EOs that provided mortality rates above 80% were submitted to chemical analysis for constituent identification. The efficient EOs were only those of C. citriodora and L. microphylla. For EO of C. citriodora, the LD80 was 7.06 ± 0.73 mg.g-1 in topical application and 5.85 ± 0.75 µL via volatile application. On the other hand, for EO of L. microphylla, DL80 was 9.95 ± 1.25 mg.g-1 in topical application and 18.56 ± 3.55 µL via volatile application. Chemical analysis showed that the main constituents were citronella for the EO of C. citriodora and (E)-caryophyllene and (E)-nerolidol to the EO of L. microphylla. EOs of C. citriodora and L. microphylla are promising for controlling S. frugiperda, with emphasis on the volatile effect of C. citriodora oil.

摘要：草地贪夜蛾（Fall armyworm, *Spodoptera frugiperda* (Smith)，鳞翅目Lepidoptera夜蛾科Noctuidae）是玉米作物的主要害虫之一，现已对化学农药及Bt技术产生抗药性。因此，精油等替代防治手段是该害虫综合治理策略实施的关键环节。本研究旨在评估柠檬桉（Corymbia citriodora）、香桃蒲桃（Myrciaria dubia，桃金娘科Myrtaceae）、小叶过江藤（Lippia microphylla，马鞭草科Verbenaceae）及伞花胡椒（Piper umbellatum，胡椒科Piperaceae）的精油（essential oils, EOs）对贪夜蛾的防控效果。研究提取了上述精油，并采用点滴法与熏蒸法，以人工饲养、取食人工饲料的30头二龄幼虫开展毒力测定试验，以蒸馏水与丙酮作为空白对照。对死亡率超过80%的精油进行化学成分分析以鉴定其有效组分。结果表明，仅柠檬桉精油与小叶过江藤精油表现出优异防控效果：柠檬桉精油的点滴法80%致死剂量（LD₈₀）为7.06±0.73 mg·g⁻¹，熏蒸法80%致死剂量为5.85±0.75 μL；小叶过江藤精油的点滴法80%致死剂量为9.95±1.25 mg·g⁻¹，熏蒸法80%致死剂量为18.56±3.55 μL。化学成分分析显示，柠檬桉精油的主要成分为香茅素（citronella），小叶过江藤精油的主要成分为(E)-石竹烯与(E)-橙花叔醇。综上，柠檬桉精油与小叶过江藤精油对草地贪夜蛾具有良好的防控潜力，其中柠檬桉精油的熏蒸防控效果尤为突出。