Ceratocystis species: emerging pathogens of non-native plantation Eucalyptus and Acacia species

Abstract

The fungal genus Ceratocystis includes many economically important tree pathogens. Until the 1980s, this genus of plant pathogens was not known from non-native plantation-grown forestry species. However, during the course of the last 20 years, a number of reports have been made of Ceratocystis spp. causing death of non-native plantation-grown forestry species from several locations worldwide. Affected trees include both Australian Acacia spp. and Eucalyptus spp. The first report of disease caused by a Ceratocystis sp. on Eucalyptus was made less than 10 years ago from Central Africa and, shortly thereafter, the disease was reported from Brazil. Subsequently, a number of other reports of Ceratocystis diseases have emerged from Africa, South America and Asia. These diseases are characterised by rapid wilt and death of trees and they have been reported to affect coppice stems as well as mature trees. In many cases, infection is associated with pruning wounds or other mechanical damage. The causal agent has been reported as Ceratocystis fimbriata s.l., but the Eucalyptus pathogen most likely represents a number of previously undescribed species. Ceratocystis spp. are vectored by wood- and bark-associated insects and typically those that visit fresh wounds, which act as infection courts. The fungi infect woody tissue and produce fruity aromas, which are attractive to insects. In this way, they can easily spread between countries and continents, thus posing a considerable quarantine threat. The biology of Ceratocystis spp. is such that diseases caused by this group of fungi are likely to become more common in the future.