分析增效系数和共毒系数的异同及探讨杀菌剂混用联合作用的评判

Analysis the similarities and differences between synergic ratio and co-toxicity coefficient and study the standard evaluating the combined action of fungicide mixture

为提出混用杀菌剂增效作用统一的评判标准,通过浸渍3-4叶期的稻苗和接种稻瘟病菌孢子悬浮液测定三环唑和硫磺按3∶1、2∶1、1∶1、1∶2和1∶3混用对稻瘟病菌的联合作用效果。用增效系数评价测定结果,发现3∶1、2∶1、1∶1和1∶2混用为相加作用,1∶3混用为拮抗作用;用共毒系数评价,则显示3∶1、2∶1和1∶1混配为增效作用,1∶2和1∶3混用为拮抗作用。增效系数和共毒系数都是以EC50和单剂在混剂中的比例进行计算,增效系数乘以100后,在数值上与共毒系数完全相等,是不同的评判标准造成了不同的评判结果。将混剂的EC50分解为三环唑和硫磺的单剂浓度,代入单剂回归方程计算的期望抑制率均大于50%,说明三环唑和硫磺混用后对稻瘟病菌没有增效作用,用Mansour的共毒因子进行计算,则3∶1、2∶1和1∶1混用为相加作用,1∶2和1∶3混用为拮抗作用。在增效系数和共毒系数计算中,EC50只对应50%的病菌抑制率,没考虑对病菌的抑制率范围,而共毒因子则涉及了抑制率范围,研究结果证实用增效系数或共毒系数再辅以共毒因子,能更准确地判断混剂的联合作用方式。

To put forward a unified evaluation standard for synergism of fungicides,the combined action of the bina-ry combinations of tricyclazole and sulfur by3：1, 2：1 ,1 ： 1 ,1 ：2 and 1 ： 3 was tested by dipping 3 ：4 leaf stage of rice seedlings and inoculating with rice blast fungus spore suspension. The results evaluated with synergic ratio showed the combinations mixed by 3 ： 1 ,2 ： 1 , 1 ： 1 and 1 ： 2 were additive action and by 1 ： 3 was antagonism,and the results evalu-ated with co-toxicity coefficient indicated the combinations mixed by 3： 1 ,2 ： 1 and 1 ： 1 were synergism and by 1 ： 2 and 1 ：3 were antagonism. Synergic ratio and co-toxicity coefficient were calculated with EC50 and the proportion of single agent in the combination,synergic ratio multiplied by 100 equal co-toxicity coefficients,the different results were caused only by different judging criterion. The EC. .of the combinations of tricyclazole and sulfur was broken down concentration of single fungicides, the expectation inhibition rate of the combinations were calculated according to the regression equation of the fungicide,and they were more than 50%, which meaned thecombinations of Magnaporthe grisea were no synergism. The combinations mixed by 3： 1 , 2 ： 1 and 1 ： 1 were additive ac-tion and by 1 ： 2 and 1 ： 3 were antagonism according to the Mansour＇s co-toxicity factor. In synergic ratio and co-toxicity co-efficients, EC 50 only responded 50% inhibition rate on rice blast fungus and did not take into account the inhibition rate range, but co-toxicity factor did it. The results indicated that the Synergism of fungicide mixture was judged more correctly through using synergic ratio and co-toxicity factor or co-toxicity coefficient and co-toxicity factor.