Insecticidal and inhibitory effects of Meliaceae and Asteraceae extracts to silverleaf whitefly

ABSTRACT Bemisia tabaci (Hemiptera: Aleyrodidae) is a polyphagous insect that causes direct and indirect damage on tomato. Spraying with synthetic insecticides is one of the main control tools for the whitefly; however, the abusive use of this tool can impact the environment and human beings. In this study we evaluated the bioactivity of extracts from plant species from Asteraceae and Meliaceae families on B. tabaci biotype B in tomato. A preliminary bioassay evaluated the effects of the extracts at 2% (w/v) on infestation and oviposition of this whitefly. Then, the nymphicidal and ovicidal effects of the chloroformic extract of Trichilia pallida - TP-Cl at six concentrations were performed. Finally, the TP-Cl LC50 was estimated. All extracts were repellent to the whitefly, except that ones from T. pallida (ethanolic) and Melia azedarach (hexanic), considered neutral at 24 h. All the extracts caused deterrence of oviposition. All concentrations of TP-Cl revealed nymphicidal activity and the highest ones provided the lowest egg viability averages. The estimated LC50 was 0.0955%. These results provide evidence for the potential of the extracts to be used as alternative control agents of B. tabaci biotype B in tomatoes.

摘要 烟粉虱（Bemisia tabaci）隶属于半翅目（Hemiptera）粉虱科（Aleyrodidae），是一类多食性昆虫，可对番茄造成直接与间接为害。合成杀虫剂喷施是防治该粉虱的主要手段之一，但该手段的滥用会对环境及人类健康产生不利影响。本研究评估了菊科（Asteraceae）与楝科（Meliaceae）植物提取物对番茄上烟粉虱B型（B. tabaci biotype B）的生物活性。初步生物测定以2%质量体积比（w/v）的提取物浓度，探究其对该粉虱侵染与产卵的影响；随后针对香桃花心木（Trichilia pallida）氯仿提取物（TP-Cl）设置6个浓度梯度，开展杀若虫与杀卵活性试验，并估算其半致死浓度（LC50）。结果表明，除香桃花心木乙醇提取物与苦楝（Melia azedarach）正己烷提取物在24小时时表现为中性作用外，其余所有受试提取物均对该粉虱具有驱避活性；所有提取物均具备产卵忌避效果。TP-Cl的各浓度梯度均展现出杀若虫活性，且高浓度组的卵存活率均值最低。经估算，其LC50为0.0955%。本研究结果证实，此类植物提取物可作为番茄上烟粉虱B型的替代防治药剂。