Chemical Control on Alternaria Leaf Spot of Schisandra Caused by Alternaria tenuissima

Fewer fungicides could be used to control Alternaria leaf spot of schisandra and the control effects of many fungicides to the disease were not determined. Therefore, the toxicity of 98 fungicides to Alternaria tenuissima was tested by mycelium growth rate method. Ten fungicides were chosen for field trial. Twenty three fungicides including cyprodinil and procymidone had stronger toxicity with EC50 values lower than 0.1 mg/L. Other ten fungicides including flusilazole had toxicity with EC50 values ranging from 0.1 to 1.0 mg/L. Based on the value of EC50 and EC90, cyprodinil and other 9 fungicides were chosen for field trials. The fungicides with higher toxicity to the pathogen indoor had also better control effect in field trial. Among them, pyrimethanil was the best with a control effect of 91.52%, followed by mancozeb, Pythium oligandrum, cyprodinil, difenoconazole azole, flusilazole prochloraz, and their control effects were 82.66%, 82.05%, 77.19%,75.43%, 81.03%, respectively, while that of hexaconazole was 58.14%.