(28(4):225-236)Studies on the resistance of diamondback moth, Plutella xylostella to commonly used insecticides

小菜蛾為臺灣十字花科蔬菜中最嚴重害蟲之一。為探究其在灣臺之抗藥現狀，曾於本省蔬菜主要產區如頂湖、蘆洲、永靖、溪湖、麻豆、鳳山、高樹、林邊、宜蘭、花蓮等地採集小菜蛾，測定其對蔬菜常用農藥Malathion、Diazinon、DDVP 、Elsan。（Phenthoate）、Phosdrin ( MevinPhos）、Thiodan（Endosulfan）等之抗藥程度，發現本蟲對此六種藥劑，已呈現不同程度之抗性。就中對多種藥劑產生多重抗性之現象，尤為可憂，此或為近年用藥無效而致小菜蛾猖獗成災之主要原因。本文除報導田間小菜蛾對上述農藥之抗性及其田間棲群抗藥程度之季節變化外，並就如何延緩抗藥性之發生問題加以討論。 The diamondback moth, Plutella xylostella L. is one of the most serious insect pests of the cruciferus vegetables in Taiwan. Application of organo-synthetic insecticides to control the diamondback moth on vegetables has been used by growers for more than twelve years. Initially, when used at recommended rates, these insecticides were effective in reducing both pest populations and damage to an acceptable level. However, their effectiveness has been gradually decling after a widespread and continuous long-term application as a result the pest population appear to be increasing rapidly. This is suspected to be a consequence of the insect having developed resistance to these chemicals. In order to understand the present status of insecticide resistance, the resistance spectra of diamondback moth strains collected from various vegetable field of Taiwan was determined by topical application using several insecticides. Most of the strains showed a relatively high level of resistance to commonly used insecticides such as malathion, diazinon, DDVP, phosdrin (mevinphos), elsan (phenthoate) and thiodan (endosulfan). The multiple resistance of diamondback moth to quite a few insecticides was also found in some field-strain. This phenomenon might be considered to be a primary obstacle to successful control of diamondback moth by several insecticides today. The implications of resistance to such a wide range of insecticides, seasonal fluctuations of insecticide resistance level in the field population and the future of chemical control of this insect in Taiwan are discussed