| Botrytis cinerea Pers is an important pathogenic fungus of plant in greenhouse and postharvest storage. Now fungicide is the main prevent method. But people pay close attention to remaining problem. Search more safer and high-performance fungicide is an urgent task. Use sensitive strain as object, effects of natamycin, carbendazim, diethofencarb, procymidone and pyrimethani against B.cinerea were tested. The activity change of fungicides under different temperatures was also tested. We have also studied the effect of natamycin on biological characteristics of B. cinerea and action mechanism of natamycin. Stability of natamycin under different test conditions was also studied. The results showed that:1 The sensitivity of B. cinerea to fungicides under 25℃was tested through mycelial growth rate method. Natamycin has good effect, EC50 value was 37.4212 mg/L, efficacy of carbendazim, iprodione and procymidone were remarkable, EC50 value were 0.6973 mg/L, 0.5315 mg/L and 0.4411 mg/L. Prochloraz, thiabendazole and pyrimethanil take the second place, EC50 value were 1.7181mg/L, 1.8432mg/L and 3.2956mg/L. The activity of diethofencarb was the lowest, EC50 value was 151.2110 mg/L.2 The sensitivity of B. cinerea to fungicides under different temperatures was tested. With temperature decrease, the effect of fungicides to B. cinerea is increase. Natamycin have good effect on mycelial growth at low temperature, EC50 value at 5℃was 0.9840 mg/L, increased 38-folds compared with 25℃. The activity of diethofencarb, carbendazim, pyrimethanil, procymidone, thiabendazole, iprodione and prochloraz to B. cinerea increased 6-folds, 10.8-folds, 9.6-folds, 8.2-folds, 4.5-folds, 4.1-folds and 30.6-folds. The activity of natamycin to spore germination at 10℃increased 2.5-folds compared with 25℃, and to sclerote germination increased 1.7-folds. The distinction of activity to B. cinerea at different growth stages was significant. Conidium was most sensitive. EC50 value of natamycin to spore germination and mycelial growth were 3.3239mg/L and 37.4212 mg/L. Activity of natamycin to sclerote germination was very weak, EC50 value exceeded 2000 mg/L.3 The toxicity to B. cinerea at different growth stages was also studied. The two fungicides have no effect on the time of spore and sclerote formation, but natamycin can restrain sporulation and sclerotigenic significantly compared with carbendazim. Carbendazim can stimulate sporulation and sclerotigenic.4 The stability of natamycin under different conditions was studied. The result indicated that ultraviolet irradiation can promote decomposition. After irradiated half an hour, utility content degradation rate was 60%. Natamycin decompose slowly in low temperature. After twenty-four hours, utility content decreased to 51.2% compared with incipient under 25℃. While, under 5℃the utility content decreased to 82.3%, degradation rate was only 17.7%. Oxidation-resistant can restrain decomposition of natamycin. After twenty days, degradation rate of CK was 68.16%. While, the degradation rate of treatment which contain oxidation-resistant was 34.84%. The result of effect on mycelial growth and spore germination under different PH value indicated that, natamycin has better effect in weak acid condition.5 Studies on action mechanism indicated that, influence of natamycin to mycelial leakage was significant. 8 hours after treated by natamycin, sugar leakage was 4 mg/g, increased 9-folds compared with incipient. Albumen leakage was 177μg/g. Conductivity was 700μs/cm. Other fungicides did not have so significant change. Among treatments of different temperatures, mycelial leakage decreased as temperature decreased. The change of treatment by natamycin was most significant. Sugar leakage after 8 hours under 5℃was 31 percents of treatment under 25℃. After treated by natamycin, the content of ergostero1 decreased. Ergostero1 content of treatment by 20 mg/L natamycin was 46.78μg/g, 55 percents of CK. Ergostero1 content decrease with temperature drop. But exocellular enzyme activity has no change.6 The result of live leaf test was identical to the toxicity of mycelium growth. The inhibitory effect of natamycin on spot expand was worse than carbendazim, but better than diethofencarb remarkably.
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