The ascospore production season ofVenturia inaequalis(Cke.) Wint., the apple black spot fungus

Abstract

Ascospore production by Venturia inaequalis (Cke.) Wint. on overwintered apple leaves was tested through spring and early summer in Nelson. Test leaves were wetted in a wind tunnel and the released ascospores were trapped and counted. Ascospore numbers rose steeply during September, and ascospore production was heaviest during late September—early November. Peak numbers occurred in October, when apple trees were at full bloom and petal fall stages. Ascospore production declined through November, December, and January, and had virtually ceased by the beginning of February.