Abstract: This paper studied the impact of several herbicides on the conidium germination of Exserohilum monoceras strain X27 in petri dish,and the synergistic effects of the pathogen and chemical herbicide quinclorac or propanil against Echinochloa crus-galli in greenhouse.The prevention efficiency of the tank-mixture of pathogen and quinclorac was also evaluated in paddy field.The results showed that test herbicides except quinclorac and bensulfulfuron-methyl could inhibit conidium germination and hypha growth to different degree.A significant synergism was observed between the pathogen and quinclorac.Adding quinclorac could obviously increase the prevention efficiency against Echinochloa crus-galli.Under field condition,the single use of pathogen could only control about 60% of the weed,while the efficiency of pathogen-quinclorac mixture could reach 90%.

Key words: Exotic pines, Decline disease, Environmental condition, Cause of disease