The Resistance and Cross Resistance of Diamondback Moth, Plutella xylostella to Bacillus thuringiensis in Taiwan

Abstract

The Bacillus thuringiensis (B.t.) resistance has been examined in diamondback moth (DBM, Plutella xylostella), and 4 strains collected from vegetable fields in north(1), central(2) and south(1) of Taiwan were compared to the laboratory-maintained susceptible strain on their sensitivities to six commercial B.t. formulations. Tests were conducted on three fixed dosages i.e., 4,000-, 32,000- and 128,000-fold dilution, from original formulations. In the susceptible strain, three designated dosages caused 96~100%, 58~97% and 41~81% mortalities in contrast to 16~100%, 0~65% and 0~31% mortalities in 4 field strains.由三重、溪湖、西螺及路竹採得之小菜蛾以六種商品化之蘇力菌配方（Thuricide、Dipel 2X、Javelin、MVP、Xentari及Turex）測試其感度，並與室內之感性品系進行比較，發現所測試的三個稀釋濃度（4,000倍、32,000倍及128,000倍）下，感性品系之死亡率分別為為96~100%、58~97%及41~81%。而田間品系在相同的三個濃度下，死亡率則為16~100%、0~65%及0~31%，顯示蘇力菌對田間小菜蛾之防治效率已經降低，而證實蘇力菌之抗藥性確實已經發生，尤其以在本省使用歷史最長之Thuricide之抗性最高，其抗性比為118.3。