Phomopsis viticola . [Descriptions of Fungi and Bacteria

Abstract

Abstract A description is provided for Phomopsis viticola . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Parthenocissus subquinquefolia (= Ampelopsis quinquefolia, = Vitis hederacea )and Vitis spp. DISEASE: Dead arm or sometimes referred to as 'excoriosis' or necrosis of grapevine. Serious outbreaks and losses have been reported in several countries (35, 508; 45, 1282; 47, 2226; 48, 549; 50, 2402; 54, 208; 54, 5021; 55, 1390, 4803; 57, 2742). The fungus invades nearly all stem tissues, particularly the medullary rays and parenchyma, causing necrotic areas extending to the centre of the wood leading to the girdling of shoots and finally resulting in dead arm condition (7, 360; 39, 369). Major symptoms are death of vines or some of the arms, progressive desiccation of stocks and shoots, stunting of leaf bearing branches, deformation and chlorosis of primary leaves, black spots on stalks and pedicels, flower abortion, drying of buds, death of spurs, stem and arm lesions or cankers or cortical necrosis and sparsity of berries (7, 360; 39, 369; 43, 3375; 48, 549, 879; 51, 547; 54, 5021). In Ontario, Canada, primary infection occurs on young green shoots and the incidence and severity depends on the inoculum potential resulting from the previous years' infection and the amount of rain in the second half of May. Primary lesions on young shoots are superficial but coalescent ones are deep seated and often become perennial (45, 332). GEOGRAPHICAL DISTRIBUTION: Africa (Kenya, South Africa); Asia (Brunei, India, Japan, Turkey); Australasia & Oceania (Australia, New Zealand); Europe (Belgium, Britain, France, Germany, Greece, Hungary, Italy, Portugal, Netherlands, Rumania, Sardinia, Switzerland, Yugoslavia); North America (Canada, USA). TRANSMISSION: By conidia liberated from pycnidia found on spurs and clusters left on dormant vines under wet conditions, when they are dispersed by rain-splash (39, 369). Also spread by nematodes and insect larvae (54, 651) and by mycelium through pruning wounds inflicted by contaminated knives (26, 95). The fungus overwinters in infected parts of the grapevine (56, 1680) as mycelium, particularly in the basal buds, (53, 636) and can carry over from the first few internodes of the same vine (5, 471).