Bagnarello Gina, Hilje Luko, Bagnarello Vanessa, Cartín Victor, Calvo Marco
Escuela de Química, Universidad Nacional (UNA), Heredia, Costa Rica.
Rev Biol Trop. 2009 Dec;57(4):1201-15.
Bemisia tabaci (Gennadius) is a polyphagous, cosmopolitan and worldwide relevant pest, mainly acting as a virus vector on many crops. A sound preventive approach to deal with it would be the application of repellent or deterrent substances hopefully present in tropical plants, which in turn may contribute to take advantage of the remarkable rich Mesoamerican biodiversity. Therefore, extracts of two wild plants belonging to family Asteraceae, titonia (Tithonia diversifolia) and "tora" (Montanoa hibiscifolia), were tested for phagodeterrence to B. tabaci adults. The crude leaf extract of each one, as well as four fractions thereof (hexane, dichlorometane, ethyl acetate, and methanol) were tested under greenhouse conditions; in addition, the extracts were submitted to a phytochemical screening to determine possible metabolites causing phagodeterrence. Both restricted-choice and unrestricted-choice experiments were conducted. In the former ones, each fraction was tested at four doses (0.1, 0.5, 1.0 and 1.5% v/v), which were compared with four control treatments: distilled water, endosulfan, an agricultural oil (Aceite Agricola 81 SC), and the emulsifier Citowett. Tomato plants were sprayed and placed inside sleeve cages, where 50 B. tabaci adults were released. The criterion to appraise phagodeterrence was the number of landed adults on plants at 48h. For the unrestricted-choice experiments, only the two highest doses (1.0 and 1.5%) of the crude extracts of each species were tested, and compared to distilled water and the agricultural oil. The titonia and "tora" crude extracts caused phagodeterrence, and for both plant species the methanol fraction stood out. Results suggest that metabolites causing phagodeterrence are several sesquiterpenic lactones, polyphenolic compounds (flavonoids and tannins) and saponins.
烟粉虱（Gennadius）是一种多食性、世界性且在全球范围内具有重要影响的害虫，主要在许多作物上充当病毒传播媒介。一种合理的预防方法是应用有望存在于热带植物中的驱避或威慑物质，这反过来可能有助于利用中美洲丰富的生物多样性。因此，对菊科的两种野生植物——肿柄菊（Tithonia diversifolia）和“托拉”（Montanoa hibiscifolia）的提取物进行了对烟粉虱成虫的拒食作用测试。在温室条件下对每种植物的粗叶提取物及其四个馏分（己烷、二氯甲烷、乙酸乙酯和甲醇）进行了测试；此外，对提取物进行了植物化学筛选，以确定可能导致拒食作用的代谢物。进行了限制选择和非限制选择实验。在前者中，每个馏分在四个剂量（0.1、0.5、1.0和1.5% v/v）下进行测试，并与四个对照处理进行比较：蒸馏水、硫丹、一种农用机油（Aceite Agricola 81 SC）和乳化剂Citowett。对番茄植株进行喷雾处理后放入套筒笼中，在笼中释放50只烟粉虱成虫。评估拒食作用的标准是48小时后落在植株上的成虫数量。对于非限制选择实验，仅测试了每个物种粗提取物的两个最高剂量（1.0和1.5%），并与蒸馏水和农用机油进行比较。肿柄菊和“托拉”的粗提取物具有拒食作用，对于这两种植物，甲醇馏分表现突出。结果表明，导致拒食作用的代谢物有几种倍半萜内酯、多酚化合物（黄酮类和单宁）和皂苷。
