Infection, hyperparasitism and conidiogenesis of Mycosphaerella lateralis on Eucalyptus globulus in Western Australia

Mycosphaerella lateralis has been isolated from diseased eucalypt foliage in conjunction with the known pathogens M. cryptica and M. nubilosa. This study sought to determine whether Dissoconium dekkeri, the anamorph state of M. lateralis, infects healthy eucalypt leaves or is a hyperparasite of M. cryptica or M. nubilosa. Detached Eucalyptus globulus leaves were inoculated with conidial suspensions of M. lateralis and the progress of leaf infection studied over 6 days. Clearing and staining of the leaves showed that infection occurred via stomata after 3 days. In order to determine whether M. lateralis is a hyperparasite of M. cryptica or M. nubilosa, colonies of these species were grown adjacent to one another on either water agar, 0.2% malt-extract agar (MEA) or 2% MEA. No evidence of M. lateralis parasitising M. cryptica or M. nubilosa was found. This indicates that M. lateralis may be a foliar pathogen, rather than a hyperparasite as was previously suggested. Scanning electron microscopy was used to show that conidiogenesis of M. lateralis is both percurrent and sympodial.