Field Control Efficiency Study of a 42%Oligose-Sulfur Suspension Agent Against Watermelon Powdery Mildew(Erysiphe cichoracearum)
A field efficacy test was conducted to clarify the ability of a 42%oligose-sulfur suspension to control watermelon powdery mildew.The results showed that a 42%oligose-sulfur suspension could control watermelon powdery mildew.The control effect reached 50.84%to 65.94%ten days after the first application,62.03%to 75.91%seven days after the second application,and 67.81%to 80.77%14 days after the second application.Among them,the control effect of high concentration(945.0 g·hm-2)and medium concentration(630.0 g·hm-2)was better than that of control agent 5%aminooligosaccharide water agent(52.5 g/hm2),and the control effect of low concentration treatment(378.0 g·hm-2)was similar to that of control agent 5%aminooligosaccharide water agent.The control effect of high-concentration was significantly higher than that of the 50%sulfur suspension agent(1 525.0 g·hm-2),and the control effect of medium-concentration treatment was similar to that of the control agent 50%sulfur suspension agent.The efficacy of the high-concentration treatment was significantly greater than that of the control agent.525.0 g·hm-2),and the efficacy of the medium-concentration treatment was comparable to that of the 50%sulfur suspension.According to the test results,it is safe for the crop within the test dose range,and a 42%oligose-sulfur sus-pension can be popularized for use on watermelon.The recommended dosage of the active ingredient is 630-945 g·hm-2,750 L of liquid per hectare,sprayed once every 10 d,and sprayed two times continuously.