Mycosphaerella ribis leaf spot on black currants in New Zealand: Perithecial maturation, ascospore release, and symptom development

Abstract

Maturation of perithecia of Mycosphaerella ribis (Fuckel) Kleb. in black currant leaf litter was studied for three winters at two sites (Edendale, Southland, 1981 & 1982; Palmerston, Otago, 1983). Ascospores began to appear in June and all perithecia contained ascospores by early September. In a spore trapping study at the same sites, and at Irwell, mid Canterbury in 1984, ascospore release always began in late August or early September, reached a peak between mid September and mid October, and declined to an undetectable level by mid November. The onset of ascospore release tended to coincide with bud burst on black currant bushes. To prevent primary infection in spring, fungicide protection should be maintained from the time leaves emerge until the grape stage of flower development. © 1989 Taylor & Francis Group, LLC.