Cryptodiaporthe populea . [Descriptions of Fungi and Bacteria

Abstract

Abstract A description is provided for Cryptodiaporthe populea . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Poplar, willow. A wide range of poplar species are more or less susceptible, with members of the tacamahacca and algeros groups principally affected. Populus alba var. pyramidalis is very susceptible in Britain and P. alba and P . tremula are tolerant; complete resistance is unknown in the genus: The fungus has been recorded on cricket bat willow in Belgium. DISEASE: Dothichiza canker, Dorhichiza dieback, poplar canker. The conidial state is the form of this fungus most commonly found associated with the dieback or canker of poplar. The fungus is a wound parasite unable to invade sound bark tissues, although very small wounds, such as scars left by bud scales, may permit infection (38, 341). Infection usually occurs in the winter, when bark moisture and turgor are lowest (36, 673; 37, 684). First signs are a discoloration of the cortex under the bark, which develops to a sunken, dead patch of bark, often at the base of twigs or at the junction of first-year and second-year wood. The lesion may have an unpleasant odour and later develops black, globular, pycnidia on the surface. The lesion may heal over in a single season but it can spread to cause severe damage or death of the host. Injury is believed to be due to toxin formation as well as physical girdling by the canker (35, 797; 38, 103). The crowns of old trees or young plants in nurseries and plantations are mainly affected. The disease may be distinguished from that caused by Valsa sordida Nits. by its larger conidia and larger and less frequent stromata in infected tissues. GEOGRAPHICAL DISTRIBUTION: Europe (all western Europe excluding Portugal, Norway, Yugoslavia, Rumania, Bulgaria, Poland, Estonia, Ukraine and south-east Russia). Near East (Turkey, Cyprus). North America (east Canada, north-east USA). South America (Argentina) (CMI Map 344, ed. 2, 1968). TRANSMISSION: Mainly by airborne splash-dispersed conidia.