Cryphonectria cubensis, the cause of a serious canker disease of Eucalyptus spp., has been reported recently in South Africa for the first time. The extensive planting of Eucalyptus grandis, which is highly susceptible to Cryphonectria cubensis, is thus cause for concern. Research conducted in this country thus far has elucidated many previously unknown facts on the biology of the pathogen. Artificial inoculation of Eucalyptus clones and hybrids in the forest and greenhouse have shown that there are significant differences in the susceptibility of various Eucalyptus clones to Cryphonectria cubensis. It is envisaged that field inoculations could eventually form the basis of a breeding and selection program. Studies to determine whether a relationship exists between the growth of Cryphonectria cubensis in trees and the availability of soil moisture, indicate that colonization by Cryphonectria cubensis of drought-stressed Eucalyptus plants is inhibited. These results are consistent with the restriction of Cryphonectria canker to high rainfall areas in Sout Africa. Pathogenicity has already been proven on an important commercial cultivar of guava (Psidium guajava) in greenhouse and field inoculations. These findings will serve as a valuable foundation for the formulation of strategies to reduce the impct of the pathogen in this country.
