Study On Pathogen Identification, Biological Characteristics And Control Of QI-Yam Anthracnose

Qi-Yam is one of the important economic crops in An-Guo and anthracnose is one ofthe diseases. The symptoms of the characteristics and the biological characteristics wassystematically studied. The fungicide was selected to control the anthracnose pathogenindoor and field.Through observing the natural infected strain from Qi-Yam, The anthracnose diseaseperiod,harm locations and the characteristics wre recorded clearly.The sample from An-Guo was identified as Colletotrichum gloeosporioides by thecharacteristics of morphology, pathogenicity test and sequence analysis of the internaltranscribed spacer region of the ribosomal DNA (rDNA ITS).The pathogen fungus mycelium growed better in PDA medium than in PYA, C-PDA,but couldn’t grow in WA medium. The fungus could grow among10～35℃, and theoptimum temperature for mycelium growth was25℃, it stopped grow at5℃and40℃.The temperture also influence the conidium germination, and the optimum temperature forconidium germination was25℃, it stopped germination at5℃and40℃. The range ofPH was2～11for mycelium growth, the optimum PH was7. The range of PH was3～8for conidium germination, the optimum pH for conidium germination was6, less than2ormore than9are not germination. Mildly acidic environment is advantageous to themycelium growth and conidial germination.According to measure the different lightcondition on the mycelium growth, the light-dark alternately is the most conductive to themycelium growth. And the conidium germination rate of under the condition of continuousdarkness higer than light-dark alternately and continuous light.The inhibitory activity of eleven fungicides and difenoconazole,pyraclostrobin withtheir mixtures at different ratios against C.gloeosporioides against yam anthracnose weredetermined by the mycelial growth rate test. It aimed to clarify the synergistic interactionof difenoconazole and pyraclostrobin against C.gloeosporioides.The results indicated inlaboratory that prochloraz,flusilazole,pyraclostrobin,propiconazole and difenoconazoleshowed higher effective to the anthracnose. Their EC50were0.0249,0.0378,0.0406,0.3941and1.2812mg/L. the synergistic effects of the2:1mixture was the most obviouswith synergistic ratio of2.41.The selected fungicides used in the field test,the results indicated:The first medicine after7days, the effective of the10%difenoconazole WDG higherthan the mixture(2:1)exhibited,but no significant difference. The difenoconazole’s controleffect was43.04%, the mixture was41.93%, significantly higher than other processing.The second medicine after7days, the fungicides exhibited higher efficacy in controllingyam anthracnose, more than50%. The third medicine after7days, the control efficative of the mixture were60.05%,79.99%and85.13%. significantly higher than other treatments,especially for the fifth medicine after7days.Its control effect was85.13%. On October22,2012, the yiled of Qi-Yam that treated the mixture was higher than othertreatments.Compared with the check plot, increase rate of45.02%. The mixture(2:1)exhibited higher efficacy in controlling yam anthracnose. The prochloraz,difenoconazole pyraclostrobin and propiconazole showed effective to the anthracnose.