Isolation of Nectria galligena from Cankers on Sweet Birch.

The fungus Nectria galligena infects many species of hardwood trees, causing "perennial canker," "European canker," or "target canker." Cultures from ascospores produced in stromata on the cankers have confirmed the pathogen species, but the fungus has rarely been successfully isolated from inside the cankers. Concern for the sweet birch trees affected by this disease in Connecticut prompted us to try isolations, using a method successful in isolating chestnut tree pathogens. Small pieces of cankered bark were stabbed into Granny Smith apples and, after incubation in boxes in the laboratory, pure cultures of N. galligena were easily removed as the pathogen slowly grew out, unchallenged, into the tissue of the apples. This technique will now be used to sample the N. galligena population in the birch populations being studied.