Fungicidal Activity Of Graphene Oxide-metalaxyl/hymexazol Composite Against Fusarium Oxysporum F.sp.cucumerinum

The pathogen of cucumber fusarium wilt is fusarium oxysporum f.sp.cucumerinum(FO),a Fusarium oxysporum of fusarium oxysporum f.sp.Metalaxyl(Met)and Hymexazol(Hym)are endoscopically applied fungicides,which are widely used to control cucumber fusarium wilt.Their application is limited by the disadvantages of rapid release,unstable property and photodegradation.Graphene Oxide(GO)is an excellent pesticide carrier because of its easy surface modification,high loading rate,large specific surface area and good water dispersion.In this study,the GO-Met/GO-Hym complex was prepared by combining Met/Hym with nano-material GO.The main results were as follows:GO-Met/GO-Hym with high drug loading,good sustained release,stability,and anti leaching performance was prepared.The drug loading of GO on Met/Hym was82.42% and 96.69%,respectively;After using GO as the carrier for Met/Hym,compared to a single fungicide,Met/Hym exhibits good sustained-release performance at different temperatures(25℃,30℃,35℃)and p H(5.0,7.0,9.0).At temperatures(25℃,30℃,35℃),the cumulative release rates of Met reached 79.95%,85.78%,and 93.95% at 168 hours,respectively.GO-Met reached 26.40%,30.16%,and 33.18% at 168 hours,respectively;The cumulative release rates of Hym reached83.98%,92.92%,and 99.89% at 168 hours,respectively,while GO-Hym reached30.39%,43.62%,and 57.85% at 168 hours,respectively.The cumulative release rates of Met at p H(5.0,7.0,9.0)for 168 hours were 90.60%,84.85%,and 94.76%,respectively.GO-Hym reached 37.39%,32.32%,and 40.84% at 168 hours,effectively improving the utilization rate of Met/Hym;In addition,GO can improve the UV photolysis resistance of Met/Hym.The half-lives of GO-Met/GO-Hym were significantly prolonged by 52.05 hours and 30.86 hours,respectively;GO-Met/GO-Hym has good stability.After cold storage at 0 ℃ and 7 days,as well as hot storage at 54℃ and 14 days,the decomposition rate of the active component content of GO-Met/GO-Hym is below 5%,showing good physical stability;In addition,GO and Met/Hym have good soil leaching resistance when compounded separately.At the end of the 10 th leaching cycle,Met/Hym leached 99% and 64% of the active ingredients,respectively,while the leaching rates of GO-Met/GO-Hym were only 8% and 4%.The fungicidal activity of GO-Met/GO-Hym to FO was tested in greenhouse and indoor.The effect of GO-Met/GO-Hym on the growth rate of FO hyphae was determined.Compared with Met/HYM,GO-Met/Go-hym had better bactericidal activity on the growth of FO hyphae.The co-toxicity coefficients(CTC)of GO-Met/GO-Hym to FO hypha growth rate were 391.16 and 356.11,respectively.The co-toxicity coefficients(CTC)of GO-Met/GO-Hym to spore germination of FO were 221.42 and 292.35,respectively.The co-toxicity coefficients(CTC)of GO-Met/GO-Hym to FO hypha biomass were 156.24 and 155.58,respectively.The protective effects of GO-Met/GO-Hym on cucumber seedlings were higher than those of Met/Hym.The control effect of GO-Met was 23.63%,31.82% and 30.91% higher than that of the control group.The control effect of GO-Hym was 13.64%,16.36%and 29.09% higher than that of the control group.