Three new species of Mycosphaerella are described from diseased leaves
of Eucalyptus growing in a species trial in south-eastern Australia:
Mycosphaerella marksii sp. nov. was associated with circular to irregu
lar, sometimes confluent lesions, bordered by a prominent red-brown ma
rgin on several species of Eucalyptus; M. grandis sp. nov. and M aggre
gata sp. nov. were associated with lesions confined to the leaf margin
, extending from the tip almost back to the petiole, on leaves of E. g
randis. It is likely that M grandis is a primary parasite and M aggreg
ata a secondary invader. The species are distinguished mainly by their
ascospore morphology and germination. Discrepancies between spore dim
ensions recorded in this and a previous study are explained by differe
nces in the stains used.