Abstract: Korean pine is the most common and important timber tree cultivated in northeastern China in recent years.But it is considerably damaged by blister rust disease.The pathogenic fungus of the disease is identified as Cronartium sp.although the taxonomic diagnosis has not been fully resolved.The fungus alternates between Pinus koraiensis Sieb.et Zucc.as its aecial host and three Pedicularis species as its telial host under natural conditions in northeastern China.Under artificial inoculation conditions,the fungus also infected three Ribes species.The pycnia appeared in early September,aecia appeared in early June next year.From June to August the Uredia were found on the leaves of lousewort.In August a great amount of telia began to form.The rates of terminal shoot growths decreased in the diseased trees by 82—94%;the lengths of needles decreased by 30%;the pH of diseased barks decreased by 0.3 and the pH of diseased older barks decreased by 0.4.The experiments of chemical control demonstrated that the application of creosote and dyrene to blister rust could kill their aeciospores;creosote,dyrene,carbondaxol and thiram could kill the germ-tubes of aeciospores too.Tests carried out in the forest indicated that to smear creosote on the surfaces of pine stems appeared to be reasonably effective. Some herbicides (viz.reglone,gramoxone,pentachlorophenol natrium,2.4.D Na,2-methyl-4-chlorophenoxyacetic acid,atrazine and fenuron etc.)could considerably killthe louseworts.