This noted on a group walk around TAFE campus
Tar Spot is a fungal disease which from the literature on line seems to particularly target Acer species. Here it is infecting Callistemon pallidus. Causes raised black spots on upper and lower leaf surface. Rarely affects the overall health of a tree, but can be widespread and aesthetically displeasing. In severe infections, can cause quite marked early leaf drop in deciduous trees like the maples. Often first starts in early summer as yellow spots which gradually gain black colour within their centres, with the black spots gradually enlarging.
The fungus overwinters on leaves that are left on ground and by spring, the spots split and release the needle-like spores which can be carried by wind to infect the nearest host.
General control can be achieved by raking and composting fallen leaves in deciduous trees. Fungicides not recommended as a cost-effective form of treatment.
Reference : Cornell University factsheet online
This is another type of tar spot Ray, found very commonly on Calistemon species. The genus is Phyllachora. Another fungal spot that is very similar to this in Australia is Sooty spot known as Placoasterella, this could also be an example.
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