Sensitivity Analysis Of Five Fungicides To Fusarium Graminearum In Shandong Province And Screening Of Mixture Synergistic Formula

Fusarium head blight（FHB）is a worldwide disease caused by Fusarium graminearum,which is popular in the middle and lower reaches of Yangtze river in China..In recent years,under the influence of climate change,crop rotation and returning straw,the occurrence of the disease shows an explosive trend in Shandong Province.The application of fungicides is the primary approach in managing FHB of wheat in production,however,the use of a single fungicide for a long period of time might make pathogens had diverse degrees in insensitivity to fungicides.Therefore,in order to control the occurrence and prevalence of FHB and alleviate the development of resistance of F.graminearum in Shandong Province,it is of important application value to screen out efficient fungicides with different mechanisms of action and synergistic formulas of fungicide mixtures.In this study,forty strains of F.graminearum from different areas of west and east Shandong were used as test isolates.For the sake of determining the sensitivity of F.graminearum to five fungicides in Shandong Province,the inhibitory effect of five fungicides on FHB was evaluated by the method of mycelial growth rate in the laboratory toxicity test.On this basis,binary compounding of fungicides with different mechanisms was conducted to evaluate the joint-toxicity of fungicide mixtures against mycelial growth of F.graminearum in eastern and western Shandong and the synergistic formulas were screened out.The results are as follows:1.There were differences in the sensitivity of the strains from the eastern Shandong regions to five fungicides.The strains’mean values EC₅₀ to carbendazim,tebuconazole,prochloraz,epoxiconazole and pyraclostrobin was 0.558±0.061μg/mL,0.675±0.110μg/mL,0.626±0.105μg/mL,2.087±0.406μg/mL and 3.412±0.830μg/mL respectively.2.There were also differences in the sensitivity of the strains from the western Shandong regions to five fungicides.The strains’mean values EC50 was 0.636±0.063μg/mL,0.882±0.153μg/mL,0.983±0.344μg/mL,2.815±0.479μg/mL and 7.873±1.713μg/mL respectively.3.The comparison of the sensitivity of the strains in eastern and western Shandong to five fungicides illustrated that the strains’mean EC₅₀ values in eastern Shandong was smaller than that in western Shandong,indicated that the sensitivity of F.graminearum to five fungicides in eastern Shandong was higher than that in western Shandong.The toxicity of five fungicides to the strains in eastern and western Shandong showed that F.graminearum was still more sensitive to carbendazim,tebuconazole,prochloraz and epoxiconazole,but it was less sensitive to pyraclostrobin.4.Fungicide mixtures showed different degree of inhibitory activity against mycelial growth of F.graminearum in eastern Shandong.Three synergistic combinations were selected from thirty-five combinations.The results proved that the mixture of carbendazim and prochloraz at the ratios of 7:1 and the mixture of tebuconazole and pyraclostrobin at the ratios of 1:5 and 1:7 had synergistic effect on the mycelial growth of the more sensitive strain CM-113 and the less sensitive strain CM-115 in eastern Shandong Province.5.Fungicide mixtures showed different degree of inhibitory activity against mycelial growth of F.graminearum in western Shandong.Nine synergistic combinations were selected from thirty-five combinations.The results proved that the mixture of carbendazim and tebuconazole at the ratios of 1:7,the mixture of carbendazim and prochloraz at the ratios of7:1,the mixture of carbendazim and epoxiconazole at the ratios of 1:7,the mixture of tebuconazole and pyraclostrobin at the ratios of 3:1,7:1,1:5 and 1:7 had synergistic effect on the mycelial growth of the more sensitive strain CM-6 and the less sensitive strain CM-254 in western Shandong Province.From the comprehensive analysis,it can be seen that the mixture of carbendazim and prochloraz at the ratios of 7:1,the mixture of tebuconazole and pyraclostrobin at the ratios of 1:5 and 1:7 showed synergistic effect on F.graminearum from eastern Shandong and western Shandong.