The Efficient Fungicides And Mode Of Action Of Them Against Wheat Fusarium Graminearum

Fusarium head blight caused by Fusarium spp. is one of the important diseases in wheat, the annual occurence area was about 7 million hm2 in China. Deoxynivalenol toxin secreted by Fusarium fungus seriously affected the health of human and animal. At present, carbendazim and other benzimidazoles was used in wheat growing areas to control Fusarium head blight in China, but its pathogen had been resistant to benzimidazole fungicides and expanded in some areas. In order to improve the control effect and delay resistance, it's need to screen more efficient and innovative fungicides of different mechanisms. The toxicities of different types of fungicides on mycelium growth, conidial germination, germ tube elongation and the spore production of F. graminearum were determined by using mycelium growth rate and conidial germination methods and the mycelium and conidial morphology shapes were observed by microscope. The joint-action of the combination of tetramycin and carbendazim and the field inoculation experiment was also conducted. The main results are as follows.1. The toxicity of 11 fungicides against mycelial growth, spore germination, germ tube elongation and sporulation of Fusarium graminearum were significantly different. The toxicities of fluazinam, tetramycin, fludioxonil, prochloraz on mycelial growth were higher, EC50?0.061 ?g/mL, and that of thiophanate-methyl, dioctyl divinyltriamino glycine and azoxystrobin were lower, EC50> 24 ?g/mL.The toxicity on spore germination of tetramycin, fluazinam, carbendazim were higher, EC50?0.394?g/mL, and that of prochloraz, thiophanate-methyl, diniconazole, difenoconazole and azoxystrobin were lower, EC50> 37 ?g/mL, fludioxonil was the lowest, EC50>1.0×104?g/mL.The toxicity of tetramycin, carbendazim, fluazinam, prochloraz and fludioxonil were higher, EC50?0.881?g/mL, and that of diniconazole, thiophanate-methyl and azoxystrobin were lower, EC50?42.977 ?g/mL.The toxicity on sporulation of fludioxonil, tetramycin, fluazinam, prochloraz and carbendazim were higher, EC50?0.360?g/mL, and that of diniconazole, azoxystrobin and thiophanate-methyl were lower, EC50?34.316 p.g/mL.2. Observed the influence of fungicides treated with EC90 on the morphology of mycelial growth and conidial germination with microscope. Fludioxonil and fluazinam treated caused the mycelial frequent increase of secondary branches, the inhibition of new branch hypha growth at the top. Dioctyl divinyltriamino glycine treated caused the increase of secondary branches, thiophanate-methyl treated caused local constriction or enlargement in mycelium. Azoxystrobin treated caused curve in the top of the mycelium. In addition, fluazinam, fludioxonil, dioctyl divinyltriamino glycine, azoxystrobin treated caused local constriction or enlargement in mycelium. All the SBIs fungcides treated with EC90 caused new branch hypha growth at the top, local constriction or enlargement in mycelium and difenoconazole treated caused the digestion of germ tube and mycelium.3. The combination (Tet4+Carl) was the most obvious synergistic one for inhibition of mycelial growth, spore germination and germ tube elongation with synergistic ratio of 4.49, 1.25 and 1.18, which showed synergistic action and additive action, respectively. All the other combinations showed summation for inhibition of mycelial growth, spore germination and germ tube elongation..4. In field trial, all the fungicides could effectively control Fusarium head blight when used three days before the inoculum of F. graminearum, the control efficacies of tetramycin, fludioxonil and fluazinam were higher than 80%, the control efficacies of other fungicides were higher than 70%. The control of tetramycin, fludioxonil, tebuconazole, prochloraz and difenoconazole were higher than 70% when used three days after the inoculum of F. graminearum while fluazinam was 50.57%.