Abstract: The root cutted seedlings of several pine species were treated with the toxin of brown spot needle blight fungus( Lecanosticta acicola), and the results showed that slash pine (Pinus elliottii Engelm.)and lobollolly pine( P.taeda L.)were very sensitive,masson pine ( P.massoniana Lamb.)was also sensitive,but japanese black pine( P.thunbergii Parl.)was not so sensitive.The results of toxin bioassay were simillar with the expression of natural infection in the field,but not totally identical.There were some differences in the reaction of slash pine resistant clones to the fungus toxin.The minimal effective concentration of the toxin was less than 100 μg/mL.The toxin was also virulent to Alternanthera philixeroides and Echinochloa crusgalli. The results suggested as though the toxin should be a kind of non host specific toxin(NHST),it actually possessed some biological specialization.