Pathogenicity of Cryphonectria eucalypti to Eucalyptus clones in South Africa.

Eucalyptus spp. are planted in many parts of the world for the production of timber and pulp, and in South Africa, they form a major component of the forestry industry. The canker pathogen, Cryphonectria eucalypti, is pathogenic to Eucalyptus spp. in Australia and Tasmania and occurs in all of the major Eucalyptus growing areas of South Africa. This study was undertaken to consider the pathogenicity of C. eucalypti to Eucalyptus clones in South Africa. Fifteen isolates of C. eucalypti were initially screened for their virulence on a susceptible Eucalyptus grandis clone (ZG14) in the field. A plot consisting of 42 different clones of Eucalyptus was subsequently challenged with a selected virulent isolate of C. eucalypti to determine whether clones differ in their tolerance to the pathogen. Results showed that C. eucalypti is capable of causing significant lesions on Eucalyptus clones and that disease development is strongly dependent on environmental factors. All of the clones tested were susceptible to C. eucalypti, but exhibited varying levels of tolerance to the pathogen. [Copyright &y& Elsevier]