ASSESSMENT OF PLATYPUS SUBGRANOSUS AS A VECTOR OF CHALARA AUSTRALIS, CAUSAL AGENT OF A VASCULAR DISEASE OF NOTHOFAGUS CUNNINGHAMII

Abstract

The potential role in Australia of Platypus subgranosus Schedl (Coleoptera: Curculionidae: Platypodinae) as a vector of the fungus Chalara australis Walker & Kile, which causes a vascular disease of Nothofagus cunninghamii (Hook.) Oerst. was studied by determining the way in which the beetle carries its mycoflora, by making direct isolations from living beetles, and by induction of beetle attack on disease-free trees and billets of N. cunninghamii. The origin of subsequent C. australis infections in these trees or billets was investigated. The relationship between the fungus and the life cycle of the beetle in naturally attacked host trees was also examined. Chalara australis was isolated from 0.6% of 2966 P. subgranosus adults and 1.2% of tunnel walls in billets were infected. Isolations from beetle frass indicated that infection of trees occurred prior to beetle attack. Because saprophytic survival of the fungus in the wood of the dead host trees is limited, there is little opportunity for the fungus to contaminate emerging brood. While a small number of beetles may possibly carry and transmit C. australis, the fungus is not dependent on the beetle for dissemination or ingression.