Taxonomy of Cronartium quercuum and C. fusiforme

SUMMARYCronartium fusiforme is considered conspecific with C. quercuum based on morphological studies, but maintained as a distinct forma specialis of C. quercuum because of its restricted host range on Pinus taeda and P. elliottii. Three other special forms of C. quercuum are proposed for physiological entities that selectively attack P. banksiana, P. echinata, or P. Virginiana. The importance of recognizing the conspecificity and genetic plasticity of these organisms when breeding resistant pines is emphasized.