Field Evaluation of Microbial and Chemical Insecticides for Diamondback Moth and Other Lepidopterous Pests Control on Cabbage

Abstract

The newly introduced experimental Bacillus thuringiensis (BT) pro-ducts and one synthetic chemical were screened in field on their efficacies to control the diamondback moth (DBM, Flutella xylostella), Spodoptera litura and Pieris rapae, and the long-used BT products and synthetic pyrethroids served as the comparing control agents. The results of two field experiments indicated that the newly commercialized SAN415-SC and other experimental BT products such as Florbac-FC, Florbac-XLV, TC0918 and CGA237218 provided better control on the DBM than other brands although suitable dosages still need to be determined. All BT products provided fair control for P. rapae. A newly developed thiourea insecticide/acaricide, Polo (diafenthiuron), performed better than any other entries in this field evaluation on both DBM and S. litura. Two tested synthetic pryethroids had not only lost their ability in controlling the DBM, also resulted in higher DBM counts by reducing both competition from other pests and the parasitization of natural enemies. 針對本省抗藥性嚴重之小菜蛾及蔬菜上其他有關之鱗翅目害蟲，以新發展出之試驗性蘇力菌（Bacillus thuringiensis）製劑及殺蟲殺蟎劑硫化尿素（thiourea），進行田間藥效測定。結果發現，新發展之成品的確較以往之商品效果為佳，對小菜蛾、斜紋夜盜蛾之防治率均較固有之蘇力菌商品提高50─100 %；而所有供試藥劑對白粉蝶之防治效果則略遜。蘇力菌製劑中，以Florbac-FC、Florbac-XLV、TC0918、CGA237218及SAN415之效果較以往使用之Thuricide、Dipel及Bactospeine更佳。硫化尿素類之新藥Polo（diafenthiuron）所表現之藥效更超過蘇力菌，惟此一化學藥劑未來可能遭遇抗性問題。Polo之兩種劑型中，Polo-SC對小菜蛾及斜紋夜盜蛾效果均佳，而可濕性粉劑配方對小菜蛾之防治效果則優於斜紋夜盜蛾。本試驗中再度證明，合成除蟲菊精類已對抗性小菜蛾完全失去防治效果，其試驗區內之小菜蛾密度甚至超過對照區，原因可能係該類藥劑不但未能造成小菜蛾之死亡，同時也減少其他害蟲與天敵對小菜蛾之競爭及寄生能力。