Eutypa armeniacae. [Descriptions of Fungi and Bacteria].
Abstract A description is provided for Eutypa armeniacae. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: As a pathogen on apricot (Prunus armeniaca) and Ceanothus spp. As a saprophyte on apricot (Prunus armeniaca), almond (Prunus amygdalus[Prunus dulcis]), apple (Malus sylvestris, walnut (Juglans regia), grapevine (Vitis vinifera), tamarisk (Tamarix sp.), Ceanothus spp. and Berberis darwinii. DISEASE: 'Gummosis' or 'dieback' of apricots in Australia (Adam et al., 1952). 'Cytosporina dieback' of apricots in California (42, 474). A contributing factor to the syndrome known as 'apricot apoplexy' in various European countries (Carter, private communications). Dieback of Ceanothus spp. in Australia and California (Moller et al., 1971). The dieback disease of apricots is also known to be associated with this pathogen in New Zealand (40, 88) and South Africa (Price, 1973). On apricot, the classical symptoms occur on trees of all ages: cankering, sometimes associated with exudation of gum, in the vicinity of wounds which expose the sapwood, most commonly those made by pruning instruments. Ultimately the leaves on the part of the branch distal to the canker wither and die, usually in mid- to late summer, typically remaining attached for many months because no abscission layer has formed. Internally, the sapwood is discoloured light brown to dark brown, with a dffluse margin. Pycnidia may appear, usually in winter, on wood and bark nearby advanced infections. The pycnidiospores have never been seen to germinate and appear to have no role in transmission of the pathogen. Perithecia are immersed in a stroma which may develop two or more years after death of a branch. The stroma may remain productive for at least six years, producing one generation of perithecia annually, maturing in early spring. In California and in South Africa, external canker symptoms were for many years confused with those caused by bacteria or the genus Pseudomonas, but the internal symptoms are usually quite distinctive and the presence of E. armeniacae has been confirmed by culturing and by serology. GEOGRAPHICAL DISTRIBUTION: Australia, New Zealand, North America (California), Europe (France, Spain, Switzerland), South Africa. Absent from Chile in a disease survey conducted by English et al. (1967). Absence of records from the Asian continent are attributed to lack of information. TRANSMISSION: Entirely by air-borne ascospores; secondary dispersal from the tree surfaces is by water-splash and run during rainfall, carrying ascospores to the vessels exposed at wounds (45, 511).
