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（Spodoptera frugiperda (Smith)，鳞翅目（Lepidoptera）夜蛾科（Noctuidae））是玉米作物的主要害虫之一，现已对化学药剂及Bt技术产生抗药性。因此，精油（essential oils, EOs）这类替代防治手段，是该害虫综合治理策略实施中的关键环节。本研究旨在评估柠檬桉（Corymbia citriodora）、卡姆果（Myrciaria dubia，桃金娘科（Myrtaceae））、小叶过江藤（Lippia microphylla，马鞭草科（Verbenaceae））及粗柄胡椒（Piper umbellatum，胡椒科（Piperaceae））的精油对草地贪夜蛾的防治效果。研究人员提取了上述四种精油，以人工饲养并采用人工饲料繁育的30头二龄幼虫为试虫，分别开展体表点滴施用与熏蒸施用两种方式的死亡率测定试验；以蒸馏水和丙酮作为空白对照。死亡率超过80%的精油将进行化学成分分析以鉴定其活性组分。结果显示，仅柠檬桉与小叶过江藤的精油表现出优异的防治效果。其中，柠檬桉精油的80%致死剂量（LD80）在体表点滴施用时为7.06±0.73 mg·g⁻¹，熏蒸施用时为5.85±0.75 μL；而小叶过江藤精油的LD80（原文笔误为DL80）在体表点滴施用时为9.95±1.25 mg·g⁻¹，熏蒸施用时为18.56±3.55 μL。化学成分分析表明，柠檬桉精油的主要活性成分为香茅素（citronella），小叶过江藤精油的主要活性成分为(E)-石竹烯与(E)-橙花叔醇。综上，柠檬桉与小叶过江藤的精油对草地贪夜蛾均具有良好的防治潜力，其中柠檬桉精油的熏蒸防控效果尤为突出。