Rhabdocline pseudotsugae is a fungal plant pathogen. The pathogen, along with Rhabdocline weirii causes Rhabdocline needlecast; R. weirii only affects Douglas-fir trees. The disease causes the needles of the tree to discolor and eventually fall from the tree. It was originally common to the Rocky Mountain states of the United States but has since spread to Europe. Infections usually start in the spring or early summer and can change the color of the foliage to a variety of hues. The fungus produces apothecia that are normally found on the underside of needles but they also occur on the topside as well.