Toxicity Of DMIs And QoIs Fungicides To Cucumber Powder Mildew From Different Regions And Enhancement Measures

Powdery mildew is an important cucurbit diease that occurs every yearthrough the whole growth season. Application of fungicides such asdifenoconazole and kresoxim-methyl is presently the principal practice in mostcucurbit crops for managing powdery mildew in China. As a result, developmentof pathogen resistance to chemical fungicides is one of the major issues onchemical disease control.1. In this paper, the toxicity of DMIs and QoIs fungicides to cucurbitpowdery mildew fungi were assessed for using a leaf-disc assay. The sensitivityof powdery mildew fungi from Shouguang, Chengyang, Feicheng, Zichuan,Yuncheng, Hengshui to difenoconazole was detected. Results shows thatChengyang, Feicheng, Shouguang was the most insensitive regions todifenoconazole. While Qingda and Feicheng was the lowest sensitive region toflusilazol, tetraconazole and tetraconazol in the sensitivity assayed to powderymildew fungi from5regions. The powdery mildew fungi from Tian’ai villagewas the most sensitive fungi to the three fungicides.In the same way, the sensitivity of powdery mildew fungi from8different regions to kresoxim-methyl was detected. The mean EC50value ofkresoxim-methyl to powdery mildew from Feicheng and Qingdao were20.8696mg/L and19.8778mg/L, and they were lower significantly than that from others.Qingda and Feicheng was the lowest sensitive region to azoxystrobin andpyaelostrobin in the sensitivity assayed to powdery mildew fungi from5regions.2. A Cotyledon tests assay was used to determine the sensitivity offungicides with other kinds of fungicides. Meanwhile, the surface tension andcontact angle were admeasured when added to functional agents Si and methyloleate. The results are as follows.Mixture of difenoconazole and kresoxim-methyl in1:9,3:7,5:5,7:3,9:1,respectively. When they at the matching of1:9,3:7,5:5and9:1, the EC50valuereduced. The synergism showed an additive action. And it is the mostoutstanding group when their blending ratio was7:3, SR＞1.5.3. A Cotyledon tests assay was used to determine the sensitivity offungicides with functional agents Si, methyl oleate. Added to functional agentsFairland2408, the mean EC50value of difenoconazole and kresoxim-methyl to powdery mildew fungi were increased to0.0076mg/L and0.0579mg/L from0.0295mg/L and0.5237mg/L, relative multiple were3.88and9.04,respectively. surface tension and contact angle reduced from72.84~67.52,34.3~37.9mN/m to0and20.8~21.6mN/m when added to functional agentsFairland2408.Added to functional agents methyl oleate in the concentration of0.01%,0.05%and0.1%, the mean EC50value of difenoconazole to powdery mildewfungi were0.4059mg/L,0.3219mg/L and0.0481mg/L, relative multiple was39.28, compard with the mean EC50value of difenoconazole1.8896mg/L.Surface tension and contact angle reduced from87.16~81.51,67.6~45.6mN/mto0and31.2~33.3mN/m when added to functional agent.