应用3种方法评价4种新氯化烟碱类杀虫剂对棉花粉蚧的毒力

Toxicities of 4 neonicotinoid insecticides to Phenacoccus solenopsis by 3 bioassay methods

【目的】探讨棉花粉蚧Phenacoccus solenopsis Tinsley的化学防治,筛选高效的防治药剂.【方法】采用浸叶法、浸渍法和药膜法评价吡虫啉、啶虫脒、噻虫嗪和烯啶虫胺4种新氯化烟碱类杀虫剂对棉花粉蚧3龄若虫的毒力.【结果和结论】40 mg·L-1噻虫嗪处理24和48 h后3龄若虫的死亡率:浸叶法为90.0%、98.8%,浸渍法为98.9%、100.0%,药膜法为85.8%、85.8%.应用浸叶法测得的4种杀虫剂对3龄若虫的相对毒力为噻虫嗪>啶虫脒>烯啶虫胺>吡虫啉,浸渍法依次为噻虫嗪>吡虫啉>啶虫脒>烯啶虫胺,药膜法依次为噻虫嗪>啶虫脒>吡虫啉>烯啶虫胺.3种方法测定结果均显示噻虫嗪对棉花粉蚧有相对较高的毒力.3种毒力测定方法中,就吡虫啉而言以浸渍法测定的毒力最高,药膜法次之,浸叶法最低;啶虫脒以浸渍法和药膜法相近,浸叶法较低;噻虫嗪浸渍法较高,药膜法和浸叶法较低;烯啶虫胺3种方法测定的毒力相近.浸渍法较好地反映了新氯化烟碱类杀虫剂对粉蚧的触杀、通过内吸而导致的胃毒等综合作用.

Objective] To study the chemical control of cotton mealybug Phenacoccus solenopsis Tinsley and to screen its efficient pesticides .[Method] The toxicities of 4 neonicotinoid insecticides （ imidaclo-prid, acetamiprid, thiamethoxam, nitenpyram） to P.solenopsis were determined by three methods： leaf dipping, nymph and leaf dipping , and the residual film method under the laboratory conditions .[Result and conclusion] The results showed that the mortalities of the 3rd instar mealybug nymphs treated with 40 mg· L-1 thiamethoxam after 24 and 48 h were 90.0%and 98.8%by using leaf dipping method , 98.9%and 100.0%by using nymph and leaf dipping method , 85.8% and 85.8% by using the residual film method.Relative toxicities of four insecticides from high to low to P.solenopsis 3rd instar nymphs through leaf dipping method were thiamethoxam , acetamiprid , nitenpyram , and imidacloprid .Relative toxicities from high to low tested by nymph and leaf dipping method were thiamethoxam , imidacloprid , acetamiprid , nitenpyram , and those for the residual film method were thiamethoxam , acetamiprid , imidacloprid , and nitenpyram .Thiamethoxam was proved to be the most efficient to P.solenopsis among these four insecti-cides .The relative toxicity of imidacloprid was the highest by nymph and leaf dipping method ;the second-ary was residual film method , and the lowest was leaf dipping method .For acetamiprid , the relative toxici-ties to the mealybug by the nymph and leaf dipping method and the residual film method were similar , while the relative toxicity of leaf dipping method was lower .The toxicity of thiamethoxam to the mealybug with the nymph and leaf dipping method was higher , and those were lower with leaf dipping method and the residual film method .The same results for nitenpyram were presented with the above bioassay methods . Nymph and leaf dipping method was proved to give the comprehensive toxicity of contact effect and stomach poisonous effect for neonicotinoid insecticides in a better way .