Laboratory toxicity of eight fungicides against Colletotrichum gloeosporioides causing walnut anthracnose

Nowadays,walnut anthracnose caused by Colletotrichum gloeosporioides is the serious and mainly diseases of walnut orchards in Shandong province.The optimum temperature for mycelial growth and conidial germination of the tested strains was measurated,and the toxicity of eight fungicides against walnut anthracnose pathogen was determined by both mycelial growth rate test and conidial germination assay in laboratory.The toxicity of prochloraz and tebuconazole to four selected strains of C.gloeosporioides under different temperatures were determined and the sensitivity of all seventeen strains of C.gloeosporioides to prochloraz and tebuconazole were screened by mycelial growth rate test.Meanwhile the protective and curative effects of prochloraz and tebuconazole were evaluated.The results showed that the optimum temperature for mycelial growth and conidial germination of C.gloeosporioides was 28℃.Under 28℃,prochloraz,tebuconazole and triadimefon had maximum toxicity against mycelial growth of C.gloeosporioides with the average EC50 value of 0.07,1.45 and 3.04 mg/L,respectively;while iprodione,mancozeb and prochloraz had maximum toxicity against conidial germination with the average EC50 value of 21.07,25.14 and 25.18 mg/L,respectively.The toxicity of prochloraz against C.gloeosporioides was not influenced by temperature,while the toxicity of tebuconazole increased when the temperature decreased.All the seventeen tested strains of C.gloeosporioides showed high sensitivity to prochloraz and tebuconazole,with mean EC50 values of 0.08 and 1.03 mg/L,respectively.It was recommended that prochloraz,tebuconazole,triadimefon,iprodione and mancozeb could be used as effective fungicides for integrated management of walnut anthracnose.