Abstract
A description is provided for Melampsora medusae. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Pycnia and aecia on Coniferae, especially Larix and Pseudotsuga, less commonly on Pinus and other genera (Ziller, 1965). Uredinia and telia on species of Populus, especially Populus deltoides, and its varieties and hybrids P. balsamifera, P. nigra var. italica and others. Its exact host range on species of Populus is not known due to confusion with other species of Melampsora and to uncertainty in the reported identity of some species of Populus and clones (Walker, Hartigan & Bertus, 1974). DISEASE: Leaf rust of poplars, causing severe leaf damage and early defoliation on susceptible species and clones. Continued defoliation of successive flushes of growth predisposes trees to winter injury and dieback (Peace, 1962) and can cause death of trees, especially nursery stock and trees 1-2 yr old (25, 204; 47, 241; Walker Haitigan & Bertus, 1974). Reduction in incremental growth of timber occurs with susceptible varieties. Some damage can occur to the conifer hosts. It is often severe on Pseudotsuga menziesii (45, 459; 47, 126) and in nurseries Pinus spp. and Larix spp. can be heavily attacked (Ziller, 1965). GEOGRAPHICAL DISTRIBUTION: North America (Canada, USA), Asia (Japan); Australasia and Oceania (Australia, New Zealand); Europe (France, Spain). Reports of Melampsora spp. on poplars (including P. deltoides and P. canadensis) from South America (Argentina, 21, 173), Uruguay (Lindquist & de Rosengurtt, 1967) may refer in part to M. medusae. TRANSMISSION: By air-borne urediniospores, often over long distances (suspected from eastern Australia to New Zealand). Urediniospores survive the winter in milder climates on semi-evergreen lines and on green sucker growth of deciduous trees. This is probably the main method of overwintering in the Southern Hemisphere and in warmer parts of the Northern Hemisphere. The possibility of bud carryover as occurs with M. epitea on Salix in Iceland (Jorstad, 1951) and the Canadian Arctic (Savile, 1972) should be investigated. Telia survive the winter and basidiospores formed in spring infect susceptible conifers in parts of the Northern Hemisphere (Ziller, 1965) but no conifer infection has so far been found in Australia.
Effective number of white shark (Carcharodon carcharias, Linneaus) breeders is stable over four successive years in the population adjacent to eastern Australia and New Zealand
