Turfgrass Diseases Survey In Changchun And Studies On The Bipolaris Leaf Spot

Through the almost two year survey,we basally mastered the kinds, the degreeof damage, distribution and pathogens of the diseases on the main cool-seasonturfgrass in Changchun. Ten diseases were found, of which the widest spread and themost harmful diseases were powdery mildew, rust, Bipolaris leaf spot and Fusariumwilt. The identification of pathogens indicated that the pathogens of the ten lawndiseases belonged to twelve species ten genera.Bipolaris leaf spot was an important lawn disease in Changchun. In order toclarify the pathogen of the disease and control the occurrence, the studies of isolationand identification, biological characteristics and epidemic of the diseases was carriedout, and the laboratory screening of fungicides were tested for controlling thatpathogen.1. The morphological observing of the pathogens indicated that Bipolaris leafspot were caused by two pathogens, B. sorokiniana and B.spicifera, in Changchun,and B. sorokiniana was the main one.2. The studies on the biological characteristics of B. sorokiniana indicated thatthe optimum temperature for mycelium growth and the the largest amounts ofsporulation were both at 30℃. The optimum PH of mycelium growth was 6, whilePH7 was the best for sporulation. Different carbon sources had different effect onacceleration of mycelium growth. Monosaccharide and disaccharide accelerated sporepruduction. Nitrogen source was important to mycelium growth and sporulation.Nitrate-N was better than ammonia-N, organic nitrogen had the worst effect. Theoptimum temperature of spore germination of the pathogen was at 25℃. Pollen,surface substance, and turfgrass sap increased spore germination.3.The incubation period and pathogenicity of Bipolaris sorokiniana weredifferent on different grass species and varieties. The ranking of incubation periodfrom short to long was Poa pratensis, Lolium perenne and Festuca rurba. Theresistance of different grass species or varieties of the same species was different, ofwhich Poa pratensis was the most susceptible, followed with Festuca rurba, Loliumperenne was the most resistant.4.Temperature, light and moisture time had much impact on spore outputs of thedisease. The largest amounts of spore outputs of the disease was at 28℃and underscattered light. The spore outputs of disease needed much long moisture time. Largeamounts of spore output after 36 hours. The spatial distribution of Bipolaris sorokiniana was aggregation distribution. The occurrence and spread of thedisease depended on mowed heights, planting density and sorts of fertilizer. Thehigher the mowed heights were, the lower the incidence rate was. The more plantingdensity was, the higher the incidence rate was. Phosphorus and potassium fertilizeradded to sorts of resistance, while the used of a lot of Phosphorus fertilizer did goodto the disease.The results of indoor fungicides screening indicated that the restraining rate oncolony growth and conidia germination of propiconazol, Prochloraz and thiram wasbest. The restraining effect of metalaxyl, iprodione and Pentachloronitrobenzene wastake second place.