| Amistar is a new fungicide used in the control of Sphaerotheca fuliginea at present. The resistance of S.fuliginea to amistar was studied by establishing its sensitivity baseline comparing the methods for testing its sensitivity. The result showed that the sensitivity with floating leaf disc test was more than with others. All the isolates from the coastal area of shanghai and Nanjing were sensitive to amistar. In order to avoiding resistance to amistar , the select pressure of single fungicide application to pathogen should be avoided.Amistar has been proved to be ideal fungicide for control of S. fuliginea with following characteristics:low applying dosage ,long-term persistence ,safety in use .The result of the floating leaf disc test showed amistar has strong toxicity to S. fuliginea. The ECso of amistar was 0.0075μg/ml,while myclobutanil 0.0102μg/ml. The result of protective effect showed the control effect of amistar treatment at 0.5μg/mK 1.0μg/ml, 2.0μg/ml and 3.0μg/ml ranged from 64.33% to 87.42%, while the control effect of myclobutanil treatment at 2.0μ g/ml was 55.97%. The curative experiment showed the control effect of amistar treated with 2.0μg/ml and 3.0μg/ml was 88.0% and 92.5% respectively ,while myclobutanil 2.0μg/ml 39.9%,48 hours spraying after inoculating . Meantime, the control effect of amistar was 69.6% and 85.7% respectively,myclobutanil 25.1%, 96 hours spraying after inoculating . amistar was regarded as the highly effective fungicide and would be used alternatively with myclobutanil and other fungicides for the control of S. fuliginea .The result of field experiment showed amistar is a ideal fungicide for control S. fuliginea . Its effective ingredient ranged from 60 μg/ml to 120 μg/ml . 120μg/ml is the best choice. The test of Duncan's showed the control effect of Amistar treated with 90 μg/ml and 120 μg/ml was better than that of myclobutanil treatment.
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