Effect and evaluation of the field efficacy test of 5% fluoro-substituted benzothiadiazole derivatives EC to watermelon and melon powdery mildew

Abstract:【Objective】Watermelon and melon are fruits with high economic value, and the diseases will affect the plant yields in seedling and adult periods, resulting in economic losses.The powdery mildew is a common disease in watermelon and melon production.Currently, the fungicides are commonly used to prevent and control this disease.However, the improper use of fungicides caused environmental pollution and drug resistance.The activator capable of inducing disease resistance is a new type of pesticide with low dosage, good effect and wide use, which has broad application prospect.Fluoro-substituted benzothiadiazole derivatives (FBT) , a new kind of activator capable of inducing disease resistance with intellectual property right in China, which is in primary research stage and needs more field experiment data to verifyits effect.In this study, the effects of resistance to watermelon and melon powdery mildew were studied to provide experimental basis for the rational use of 5% fluoro-substituted benzothiadiazole derivatives EC【Methods】In 2016, to the screening experiments of 5% FBT inducing conditions was conducted in Yang town Shunyi district and Kangzhuang town Yanqing district in Beijing.The leaf spraying method was used in this study.The concentration of 5% fluoro-substituted benzothiadiazole derivatives EC was set as follow:100, 50, 25, 10 mg·kg-1.The seedlings were sprayed every 7 days and for 3 times continuously.The induction times of 5% fluoro-substituted benzothiadiazole derivatives EC was set as follow:3, 5 and 7 times.The seedlings were sprayed every 7 days at concentration of 25 mg·kg-1.Then, the assay of 5% fluoro-substituted benzothiadiazole derivatives EC optimal application conditions was conducted in Institute of Vegetable Flower Institute, Chinese Academy of Agricultural Sciences.The concentration of 5% fluorosubstituted benzothiadiazole derivatives emulsifiable concentrater EC was set as 10 mg·kg-1, the seedlings were sprayed every 7 days and for 5 times continuously.【Results】The control efficacy of 5% fluoro-substituted benzothiadiazole to watermelon and melon powdery mildew was increased with the increase of concentration and the number of application of FBT.For the melon powdery mildew, the control efficacy of5% fluoro-substituted benzothiadiazole derivatives EC at the concentration of 100, 50 and 25 mg·kg-1 were significantly higher than the fungicides 40% fluorosilicone EC;For the watermelon powdery mildew, the control efficacy of 5% fluoro-substituted benzothiadiazole derivatives EC at the concentration of 100 mg·kg-1 and 50 mg·kg-1 were significantly higher than the control fungicide 40% fluorosilicone EC.However, 5% fluoro-substituted benzothiadiazole derivatives EC at the concentration of 100 mg·kg-1 or 50 mg·kg-1 caused phytotoxity, and affected yields of watermelon.The control efficacy of 5% fluoro-substituted benzothiadiazole derivatives EC on the induction of watermelon powdery mildew was the best (97.5%) at the concentration of 10 mg·kg-1, 5 times and the induction interval of 7 days.Activated benzothiadiazole (BTH) and control fungicide 42.8% fluopyramtri·floxystrobin ester EC suspension had no significant difference.The control efficacy 5% fluorazole activated ester EC was the best (63.89%) of the induced resistance to melon powdery mildew at the concentration of 10 mg·kg-1, induced 5 times and the induction interval was 7 days.5% fluoro-substituted benzothiadiazole derivatives EC was 69.16% when the concentration was 10 mg·kg-1, induced 5 times and the induction interval was 7 days.The control efficacy to watermelon powdery mildew was the best.【Conclusion】5% fluoro-substituted benzothiadiazole derivatives EC had significant effects on western melon powdery mildew, and its optimal induction concentration was10-25 mg·kg-1, the optimal induction time was 5 times.