Application of the Uniform Experimental Design to Obtain the Optimal Synergistic Mixture Ratio of Combined Pesticides

Bioassay was arranged with uniform experimental design method to study the combined synergism of cypermethrin and quinalphos on the 2nd instar larvae of common cutworm, Spodoptera litura . The relationship between the death probability of target insect and the dosages of the insecticides was described as a quadratic polynomial. The mathematical relationship between co toxicity coefficient (CTC) and the dosages of the insecticides (N 1, N 2 ) was deduced from the calculating formula of CTC, i.e. CTC=100/(N 1/a) (N 2/b), where a, b represent the medium lethal concentrations of cypermethrin and quinalphos, respectively. The formula: j=(N 1/a) (N 2/b) , was taken as the goal function of optimization problem. Finally, the maximum CTC and optimal mixture ratio of cypermethrin and quinolphos were obtained by using the program, NLP of SAS.