Investigation On Walunt Fungal Disease In Northwest Guangxi And Control Of Walnut Anthracnose

The distribution,pathogen and hazardous degree of walnut diseases were investigated in Fengshan County?Huanjiang County and Jinchengjiang County of Hechi City and Leye County of Baise City during 2015 to 2017.Biological characteristics of pathogen of walnut anthracnose,fungicides against pathogen of walnut anthracnose and control in field were researched.The results were as follows:1.Pathogen identification of walnut fungal diseasesIt was showed four walnut fungal diseases occurred in Northwest Guangxi,which included walnut root rot,walnut twig blight,walnut Phoma leaf spot and walnut anthracnose after being surveyed for two years.It was first time that pathogen of walnut root rot was identified as Fusarium solani,pathogen of walnut twig blight was identified as Phomopsis juglandina,pathogen of walnut Phoma leaf spot was identified as Phoma sp.based on the results of pathogenicity test,morphological character,homology comparison of ITS sequences,and five isolates of pathogen of walnut anthracnose were identified as Colletotrichum gloeosporioides based on the results of pathogenicity test,morphologentic characters,multigene homology comparison and multi-gene phylogenetic analysis based on five sequences which included ITS,ACT gene,CHS-1 gene,TUB2 gene and GAPDH gene in northwest Guangxi.2.Occurrence and degree of damage of walnut anthracnoseField investigation showed walnut anthracnose was the most serious on walnut in northwest Guangxi.Disease rate of walnut anthracnose was from 20%to 100%,incidence of anthracnose in several walnut nursery was over 90%,disease index of walnut anthracnose ranged from 5 to 90,incidence and severity of walnut anthracnose were big different between different walnut varieties,which only disease index of Juglans sigillata was the lowest and disease index on other varieties were high.3.Biological characteristics of pathogen of walnut anthracnoseBiological characteristics of pathogen of walnut anthracnose were tested and it showed that temperature for mycelium growth ranged from 10 ? to 40?,and the optimum temperature was 25 ?;the temperature for conidial germination ranged from 10? to 40 ?,and optimum temperature was 28 ?;pH values for mycelium growth ranged from 3 to 10,and optimum growth pH value was 7;pH value for conidia germination ranged from 4 to 9,and optimum pH value was 7;PDA medium was the most suitable medium for mycelium growth,and OMA medium was the least suitable medium for mycelium growth among being tested media;PDA medium was the most suitable medium for sporulation and COA medium was the least suitable medium for sporulation among being tested media;darkness benefited mycelium growth;?For strain TA3-4.the lethal temperature for mycelium was 65 ? 10 min and for conidial was 63 ? 20 min.4.Results of screen of fungicides and biological controlling agents against pathogen of walnut anthracnose in roomToxicities of five fungicides were tested and it showed that the maximum toxicity against mycelium growth was tebuconazole>azoxystrobin>difenoconazole>prochloraz>pyraclostrobin and best fungicides was tebuconazole,which EC50 to TA3-4 and TB5-2 were 0.0561mg/L and 0.0605mg/L,respectively.Biological controlling agents against pathogen of walnut anthracnose were screened and it showed that Bacillus subtillis B11 was the best agent which inhibition rate were more than 48%.5.Results of field control experimentTree fungicides were chosen to apply in field and it showed that control efficiency of 25%tebuconazole was 82.23%,azoxystrobin was 80.26%and 43%pyraclostrobin was75.98%.