Chemical and biological insecticides:Resistance mechanisms and management in diamondback moth




The diamondback moth(DBM),Plutella xylostella L.,is a highly injurious,cosmopolitan pest of cruciferous crops.A well-known reason for this pest status is its remarkable ability to rapidly evolve insecticide resistance.When a new compound becomes available,growers may adopt it because of inability of existing insecticides to provide adequate control;but over-use and the absence of management strategies usually result in the appearance and spread of new resistance from focal points to wider geographic areas.DBM was the first species to develop resistance to Bt toxins in open field populations.Overuse of Bt sprays was responsible;and future attempts to control DBM using Bt-expressing transgenic plants must be mindful of this precedent.Resistance management strategies may attempt to delay the onset of resistance,such as the high-dose/refuge strategy employed for pests of transgenic Bt-cotton,or to manage existing levels of resistance to economically sustainable amounts when it has already appeared. The latter approach.such as when rotations are employed,is successful only when resistance carries with it a substantial fitness cost in the absence of insecticide,and the magnitude and types of such costs are in general poorly known.Combinations of chemical insecticides or“pyramiding”of insecticidal genes in plants can delay the onset of resistance,but if DBM has already developed some resistance to one of the components,the effectiveness of this strategy is compromised.One approach that deserves more attention is the exploitation of the key adaptation by which DBM detoxifies glucosinolates in its cruciferous hostplants.A highly active sulfatase expressed in the midgut has been shown to cleave off the sulfate group,preventing activation of the glucosinolate to more toxic compounds by the myrosinase enzyme of the plant. This sulfatase has not been detected in any other insect,and may be unique to DBM;thus targetting this enzyme may provide a highly specific method of control.
机译:小菜蛾(Plutella xylostella L.)是十字花科作物的一种高度伤害性的世界性害虫。造成这种害虫状态的一个众所周知的原因是其迅速发展出对杀虫剂的抗性的显着能力。当有新化合物出现时,种植者可能由于现有杀虫剂无法提供足够的控制而采用它;但是过度使用和缺乏管理策略通常会导致新的抗药性出现并从焦点转移到更广泛的地理区域。DBM是第一个产生抗药性的物种过度使用Bt喷雾剂是造成这种情况的原因;将来使用表达Bt的转基因植物控制DBM的尝试必须牢记这一先例。抗药性管理策略可能会试图延缓抗药性的发作,例如高抗药性。 -转基因Bt-棉害虫的剂量/避难所策略,或管理已经对经济上可持续的数量产生抗药性的现有水平出现了。后一种方法(例如采用旋转方式)只有在没有杀虫剂的情况下抵抗力会带来相当大的适应性成本,而这种成本的大小和类型却鲜为人知。化学杀虫剂或“金字塔”的组合植物中的杀虫基因可以延缓抗药性的发作,但是如果DBM已经对其中一种成分产生了抗药性,那么该策略的有效性就会受到损害。一种值得更多关注的方法是利用关键的适应性方法DBM对十字花科寄主植物中的芥子油苷进行解毒。已证明中肠中表达的高活性硫酸酯酶会裂解硫酸根基团,从而防止芥子油苷被植物的黑芥子酶分解为更具毒性的化合物。该硫酸酯酶在其他任何昆虫中均未检测到,可能是DBM所独有的;因此,以该酶为目标可提供一种高度特异性的防治方法。



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