Quambalaria leaf and shoot blight onEucalyptus nitensin South Africa

Abstract

Quambalaria spp. cause leaf and shoot dieback diseases on young Eucalyptus trees in Australia, Thailand, South America and South Africa. The disease was first recorded in South Africa in the early 1990s but has been restricted to nurseries in the subtropical north-east coastal area of the country, without resulting in great effect. Recent disease surveys in the Mpumalanga Province of South Africa have revealed extensive shoot and leaf dieback, as well as stem cankers on 1-year-old E. nitens trees. Some symptoms of the disease resembled Quambalaria leaf and shoot blight. However, this was the first time it had occurred on the stems of larger trees, on E. nitens or in the cold temperate region of the country. The aim of this study was to identify the causal agent of the disease and to test different Eucalyptus spp. and clones of relevance to the South African forestry industry for their susceptibility to the pathogen. Comparisons of DNA sequence data for the ITS and 5.8S regions were used to identify the fungus. Results showed that the pathogen represented Q. eucalypti. Inoculation trials showed that all the material tested was susceptible to infection by Q. eucalypti. This study shows that Q. eucalypti has become elevated from a relatively minor nursery pathogen to one that can cause significant damage on a wide range of Eucalyptus spp. in both temperate and sub-tropical areas of South Africa.