Biology and control of the fungus Diplocarpon earliana (Ell.& Ev.) Wolf on strawberries

During three years of trials (1998, 1999 and 2000) the appearance of leaf red spot or leaf scorch (Diplocarpon earliana ; anamorph Marssonina fragariae) on strawberry leaves was monitored as well as the possibilities of control. The trials were conducted in strawberry plantations on the cultivar Marmolada in Katoličko Selišće at Popovača. By monitoring the biology of the pathogen we tried to determine: the overwintering manner, the beginning of the formation of fruiting bodies (apothecia and acervuli), the beginning of primary infections and the appearance of the first symptoms. The fungus was isolated in the laboratory of the Department of Phythopathology of the Faculty of Agriculture Zagreb by using the customary methods on PDA agar. The determination was performed on the basis of the morphology of fruiting bodies and spores. The fungicide efficacy trial was conducted according to the random block scheme in four repetitions in accordance with OEPP/EPPO (1997) recommendations. We determined that the fungus overwinters in the mycelium form. In early spring both types of fruiting bodies are formed ; apotheci and acervuli, so the primary inoculum can also be ascospores and conidiospores from the acervuli. During further vegetation the fungi forms only acervuli, i.e. it appears only in the form of the anamorph stage Marssonina fragariae (Lib.) Klebhan, so all further secondary infections are with conidiospores. The first symptoms appear after only a few days after the discharge of the first spores, at the beginning of May, in the form of red spots. Among the fungicides in the trial agents Folicur M 50 WP(tebuconazole+tolilfluanid) and Kidan SC (iprodione) gave the best efficacy, while agents Euparen M WP (tolilfluanid) and Quadris KS (azoxystrobin) gave medium efficacy.