Identification And Study On Fungicides Control Of Boeremia Exigua,Pathogen Of Polygonatum Kingianum Leaf Spot Disease In Pu’er City

Polygonatum kingianum Coll.et Hemsl.leaf spot disease is a common fungal disease in production,with a high incidence,which seriously reduce its output and quality,hindered its sustainable development.In order to understand the occurrence of Polygonatum kingianum leaf spot disease in Pu’er,and to provide a theoretical basis for the planting of Polygonatum kingianum and the prevention as well as the treatment of leaf spot disease,this paper investigated leaf spot disease,identified the pathogen,studied the prevention and treatment effect of different fungicides in Pu’er.The main findings are as follows:According to the survey of seven Polygonatum kingianum planting areas in Pu’er City,found that Polygonatum kingianum leaf spot disease mainly occurred in the field planting area,the incidence and disease index were as high as 86.50% and 39.32.High temperature in the rainy season from July to August is the high incidence period.Serious cases caused the aerial part of Polygonatum kingianum to dry up and die.Two distinctively dominant bacterial strains,HJYB001 and HJYB002,were isolated from the collected sample leaves.Through pathogenicity test,HJYB001 was confirmed as the causative bacterium of Polygonatum kingianum leaf spot disease.Observed on OA medium,the HJYB001 colony is gray-green,with gray-white edges,and the pycnidium is(nearly)sphericall,90 μm~156 μm,with an orifice,which contains a large number of small conidia,in the shape of oval,ovoid and pyriform,3.9~7.1 μm×1.3~3.2 μm,colorless,transparent,smooth,containing 2 to 3 oil globules,most of which have no diaphragm,and very few have 1 to 2 diaphragms.Whilst,the gene sequence of ITS,was gauged,then compared with BLAST.It was found that the similarity between HJYB001 strain and Boeremia exigua was 100%.Combined with the morphological characteristics of the pathogen and ITS sequence analysis,HJYB001 was identified as B.exigua.Study on Fungicides Control of Boeremia exigua,pathogen of Polygonatum kingianum Leaf Spot Disease.The results show that chemical agents 10% hexanozol SC and 10% difenoconazole WG against B.exigua had the highest indoor toxicity,EC50 values of 0.1047 ug/m L and 0.1549 ug/m L respectively.Compared with 0.5% physcione AS,the relative virulence index was as high as 862.55 and 583.01,and the biological agent 0.3%tetramycin AS had a higher indoor toxicity,EC50 value was 0.3343 ug/m L,and the relative virulence was 270.14.In the pot plant prevention and treatment experiments,10%difenoconazole WG and 10% hexaconazole SC had the best preventive and therapeutic effects on Polygonatum kingianum leaf spot disease,and in the prevention test,the preventive and therapeutic effects were 81.34% and 70.83%,in the treatment test,the preventive and therapeutic effects were 57.73% and 53.36% respectively.The field preventive and therapeutic effects demonstrated that after three times of application,80%mancozeb WP 1600 times liquid and 10% hexaconazole SC 2000 times liquid had the best preventive and therapeutic effects,with 71.34% and 68.20%,respectively.