[ Objective ] To overcome the resistance of Phytophthora parasitica var. nicotianae towards metalaxyl and effectively eontrol its damage,new efficient complex agent of metalaxyl was studied and developed. [ Method ] The toxicities of nine fungicides against P. parasitica were meastned using growth rate method. On this basis,the fungicides with good effects were selected to complex with metalaxyl ,and the optimum complex ratio was confirmed. [ Result ] The toxicity of metalaxyl was the strongest with EC50 of 2. 130 5 μg/ml ;followed by Carbendazim, Mancozeb and Dimethomorph with EC50 of 2. 357 9,2.639 8 and 2.778 8 μg/ml. The effect of Cyazofamid was the poorest with EC50 of 6. 278 08 μg/ml. The optimum complex ratios of Dimethomorph,Carbendazim and Mancozeb with metalaxyl were 40:60,30:70 and 20:80, and their co-toxicity coefficients were 138.80,124.25 and 115.00,respectively. [ Conclusion ] The complex had application and promotion value, which could be used to carry out further field trials.%[目的]为克服烟草黑胫对甲霜的抗药性,有效控制其危害,研究开发新甲霜灵高效复配剂.[方法]采用生长速率法测定了9种杀菌剂对烟草黑胫病菌的毒力,并在此基础上选取效果较好的杀菌剂与甲霜灵进行复配,确定最佳复配比.[结果]甲霜灵的毒力最强,EC50为2.1305μg/ml,其次为多菌灵、代森锰锌和烯酰吗啉,EC50分别为2.3579、2.6398、2.7788μg/ml.氰霜唑的效果最差,EC50为6.2788μg/ml.效果较好的烯酰吗啉、多菌灵、代森锰锌3种杀菌剂与甲霜灵的最佳复配比分别为40:60、30:70和20:80,其共毒药系数分别为138.80、124.25和115.00.[结论]复配剂具有推广应用的价值,可进一步开展大田试验.
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