Infection of the Native California Grass, , by , the Cause of Pitch Canker in Pines.

At Point Reyes National Seashore in California, , the causal agent of pitch canker in pines, was isolated from , the California native grass, , and the introduced grass, . All grass plants from which was isolated were symptomless. Pathogenicity of grass isolates was confirmed by inoculation of trees, which developed symptoms similar to trees inoculated with a pine isolate of . Isolates from grasses were somatically compatible with isolates recovered from symptomatic pines. grown in a growth chamber was inoculated with a green fluorescent protein-expressing strain of . Segments of inoculated leaves were incubated in moist chambers; after 1 to 2 days, sporulating hyphae were observed growing from leaf tissue. Spores of removed from leaves were confirmed to be fluorescent when illuminated with ultraviolet light. These results raise the possibility that cryptically infected by may be a source of propagules capable of infecting pines.