Growth and Stromata Production of Hypovirulent and Virulent Strains of Cryphonectria Parasitica on Dead Quercus Rubra and Acer Rubrum

Abstract

Dead red oak (Quercus rubra) and red maple trees (Acer rubrum) that had been girdled were inoculated with one virulent and six hypovirulent strains of Cryphonectria parasitica. Bark samples were removed from specific points on the trees and fungi from them were subsequently cultured to determine the potential for survival and growth of the C. parasitica strains. All seven strains survived up to ten months after inoculation on red oak. Virulent strain 5-9-IB was recovered from oak bark plugs with a higher frequency than any of the hypovirulent strains but produced low numbers of stromata. Hy? povirulent strains that produced the highest rates of stromata on dead red oaks were more frequently reisolated. Survival of all seven strains on red maple stems was very poor. Seven months after stem inoculations, approximately 0.5% ofthe bark plug samples yielded reisolations of C. parasitica. Only strain Ep 88 produced a few stromata during one sampling date on two red maple trees. Survival of hypovirulent strains of Crypho? nectria parasitica (Murr.) Barr on different tree species may be essential for control ofthe chest? nut blight organism. The first collection of the fungus on a host other than American chestnut (Castanea dentata [Marsh.] Borkh.) was ob? tained by J. Franklin Collins at Martic Forge,