A SERIOUS CANKER DISEASE OF EUCALYPTUS IN SOUTH-AFRICA CAUSED BY A NEW SPECIES OF CONIOTHYRIUM

Eucalyptus spp. are being propagated extensively as exotics in plantat ions in South Africa, and many other parts of the world. In South Afri ca, a number of diseases result in serious losses to this resource. Th is paper describes a new and very damaging stem canker disease, which has recently appeared on plantation-grown eucalyptus in South Africa. The disease, first noted in an isolated location in Zululand is now co mmon in other parts of the country, and is typified by discrete necrot ic lesions on stems. These lesions coalesce to form large, gum-impregn ated cankers and malformed stems. The causal agent of the disease, as inferred from pathogenicity tests, is a new species of Coniothyrium de scribed here as C. zuluense. This fungus is a serious impediment to eu calypt propagation in South Africa, and is most likely a threat to sim ilar forest industries elsewhere in the world.