A Twig Canker on English Hawthorn Caused by Coniothyrium sporulosum in Italy

Large, open, irregularly-shaped cankers on trunks and twigs of 4- to 12-year-old Crataegus monogyna Jacq. in a mixed oak forest in northern Italy were observed in 2001. Radial sections through the cankers, which often occurred at sites of hail damage from the previous year, showed a brown discoloration in the xylem. Foliage distal to the cankers became chlorotic, wilted and finally died. When the disease was severe, the entire top of the plant died, and epicormic shoots developed below the cankers. No fruiting bodies were present on the canker surface, nor were symptoms observed on root collars or roots. Microscopic examination of cankers showed that vessels frequently contained mycelium. Among a variety of microorganisms isolated from the necrotic tissues, Coniothyrium sporulosum (Gams & Domsch) van der Aa was isolated from 100% of the chips. The present work adds the genus Crataegus to the wide list of hosts (i.e. Rubus, Malus, Quercus, Picea, Taxus, Juniperus, Chamaecyparis, Cupressocyparis, Mahonia) susceptible to C. sporulosum, which may act as an important pathogen under forest conditions, in orchards, and in breeding programs.