Rhizosphaera pini is a common plant pathogen in the Lake States, Northeastern States andCanada. A closely related pathogen, Rhizosphaera kalkhoffii, causes a common needle blight on spruce and other conifers. R. pini is often considered to be a weak pathogen,occurring on stressed foliage or foliage killed by other causes. However, it has been observed causing significant damage on balsam fir and Fraser fir. It appears to be particularly damaging in shaded, damp areas and when the trees are under other stress.