P-397 - Is Cryphonectria radicalis more aggressive than Cryphonectria parasitica on red and white oak species?

Oak species (Quercus spp.) occupy >70% of West Virginia’s forests. Cryphonectria parasitica, the causal agent of chestnut blight, infects numerous oak species, but causes less disease than on American chestnut (Castanea dentata). Cryphonectria radicalis, a close relative, also infects oaks and select reports indicate is more aggressive on oak than C. parasitica. However, direct comparisons between the two Cryphonectriaspecies have not been formally undertaken. Because red oak family members are more susceptible to C. parasitica than white oak, we sought to investigate if this trend held true for C. radicalis on red and white oak. We field tested strains of C. parasitica and C. radicalis on chestnut oak (Quercus montana; white oak family) and red oak (Quercus rubra; red oak family) by inoculating 30 trees per species with two strains of both Cryphonectria species along with a negative control treatment. After six months, we found that C. parasiticastrain EU12 was the only strain to produce significantly larger cankers on red oak compared to all others. Incidence of recovery of EU12 from red oak cankers was 42% while all other treatments were much lower. Cryphonectria parasitica appears to be the more virulent pathogen compared to C. radicalis, yet both pose minimal threats to red oak and no apparent threat to chestnut oak. Cytospora ceratosperma was also found in many of the negative controls and may pose a more serious threat than Cryphonectria species on oak. Follow-up studies on red oak are currently underway to confirm our previous findings.