AERIAL PHOTOGRAPHS REVEAL CHESTNUT-BLIGHT FOCI

Infrared photographs of a chestnut (Castanea sativa) stand of northern Switzerland which was severely infested by Cryphonectria parasitica w ere evaluated to document disease progress. Two original infection foc i were identified in the photographs. These foci were strongly correla ted with the distribution of the two vegetative compatibility groups o f C. parasitica strains found there, suggesting that two independent i ntroductions of the fungus occurred within this stand.