| Corn is one of the main cereal crops, and its amounts of planting are rank the third which next only to the wheat and rice. Southern corn leaf blight is the most important fungal diseases for corn which greatly influence the yield and quality. Azoxystrobin is developed by Syngenta, which is a fungicide with the characters of efficient, low mammalian toxicity, low residual and environment friendly. The study was conducted by using the azoxystrobin of strobilurin fungicide. The sensitive of southern corn leaf blight to azoxystrobin and the synergistic effect of SHAM and azoxystrobin were examed in the laboratory. The sensitivity baseline was constructed for further study the field efficacy of Amistar to the important fungal disease of corn. The aim of the study is to evaluate the field efficacy of Amistarto the fungal diseaseof corn and best does of the fungicide in order to porvived theoretical gudilines for the plant disease's prevention of corn.The sensitivities of 20 isolates of B. maydis to 7 fungicides were examined. The results shown that fluazinam and flusilazole has the best effect to inhibit the growth of the mycelium, and the EC50 was 0.0295±0.0040 ?g/m L and 0.0145±0.0010 ?g/m L, respectively. Difenoconazole, prochloraz and tebuconazole ranked the second, and the EC50 was 0.0929±0.0090 ?g/m L, 0.0916±0.0134 ?g/m L and 0.2146±0.0191 ?g/m L, respectively. The inhibitory effect of chlorothalonil and azoxystrobin was relatively worse, and the EC50 was 2.3518±0.214 ?g/m L and 1.4885±0.3091 ?g/m L, respectively. There were no significant effects on the same fungicide between different strains.The sensitivities of 98 strains of B. maydis to azoxystrobin were examined using the spore germination method. The EC50 is ranging from 4.1559 to 691.4320 ?g/m L and the average value is 171.2762±19.4221 ?g/m L. The EC50 was 0.0007 to 9.0220 ?g/m L when 100?g/m L SHAM was mixed. The activities of azoxystrobin were significantly enhanced when 100?g/m L SHAM was mixed. The average EC50 is 1.3639±0.1889 ?g/m L when the abnormal values were excluded. Upon examination are in the line with normal distribution, the average value can be used as the sensitive baseline of the B. maydis to azoxystrobin(+SHAM).The results of field experiment revealed that, the first spraying azoxystrobin 40?80?120 and 160 ?g/m L on Huamei sweet No.8 which was infected serious diseases with southern leaf blight, 7 days later, the disease control efficiency were 22.94 to 45.17%; And the second spraying azoxystrobin, the disease control efficiency was 35.77 to 67.2% after 7 days; and the third were 43.51 to 75.39%. However, the first disease control efficiency of southern leaf blight on Huamei cereal 7th which have light diseases were 48.54% after 7 days later, the second disease control efficiency were 27.75 to 76.02%, and the third were 24.50 to 73.97%.Azoxystrobin, as well as kresoxim-methyl, were applied to control corn southern leaf blight of waxy corn of Huamei No.7. The azoxystrobin 36?72?107 and 142 ?g/m L which was infected serious diseases with southern leaf blight, 7 days later, the disease control efficiency were 51.65~87.18%; And the second spraying azoxystrobin, the disease control efficiency were 20.10 to 50.46% after 7 days; and the third were 23.68~69.92%%. However, The kresoxim-methyl 72?107 and 142 ?g/m L which was infected serious diseases with southern leaf blight, 7 days later, which have light diseases were 56.28 to 93.37% after 7 days later, the second disease control efficiency were 9.51 to 64.16%, and the third were 7.05 to 47.61%. The control effects to corn southern leaf blight of all treatments were increasing and control effect could last more than 14 d. The corn yield of all treatment was increasing(up to 18.84% yield increase) by using the azoxystrobin and kresoxim-methyl. |
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