| Abstract: In order to take advantages of the characteristics of plant active substances, such as insecticidalefficacy, sterilization, antiviral property, weeding, etc., and achieve the purpose of not destroying the ecologicalenvironment and retarding the drug resistance of the target creature, a mixed water agent composed of activesubstances of multiple plants which extracted from phellodendron bark, Chinese rhubarb, turpentine, aloe,saponin, chinaberry root was used in the experiment. The toxicity determination of powdery mildew fungus ofcucumber was studied. The field efficacy test and safety evaluation of powdery mildew of cucumber, pumpkinand watermelon were conducted. The results showed that mixtures of various plant active substances had stronginhibitory effect on the powdery mildew of cucumber, the EC50 value of its inhibitory activity was 5.981 7. Thecontrol effects of powdery mildew on cucumber, pumpkin and watermelon were enhanced with the increase ofconcentration, and the control effects of 400 times diluted mixtures were 75.8%, 76.7% and 78.1%, respectively,which indicated that the mixtures were safe for the growth of the above melons. |