Hi @John57
Sorry to be the bearer of bad news, but your apple tree is affected by Apple Scab, a fungal disease that is quite prevalent in Australia.
According to the Victorian Department of Agriculture: "The disease can reduce the quality and size of fruit. It can also cause premature fruit drop, defoliation and poor development of fruit buds in the next season. Under favourable conditions and without control measures, apple scab can cause total crop failure.
"The apple scab fungus usually survives over winter under the trees, in the dead, infected leaves from the previous season. Occasionally, twig infections, infected bud scales or infected leaves that remain on the tree over winter can provide an overwintering source of spores. Leaves infected with the apple scab fungus usually fall from trees in autumn or early winter.
"The fungus continues to live within the leaves during winter, forming small, flask-shaped bodies, in which spores (ascospores) develop. These ascospores mature in spring and are forcibly ejected during spring rains.
The time when ascospores mature coincides with the period of rapid development of buds, flowers and leaves. Ascospore discharge occurs over a period of about 8 to 12 weeks. Mature ascospores are present by early September, and the greatest numbers of ascospores are released from late September to mid-November. This is the high-risk period for infection with apple scab."
The main methods of control are:
- using protectant and post-infection sprays in spring
- sanitation practices to reduce scab carryover.
Protectant sprays of suitable fungicides are needed at green tip, pink bud and at regular intervals afterwards. This is to make sure that rapidly developing leaves and fruits are covered with a fungicide residue that will prevent spores from germinating.
Most fungicides won't cure an established apple scab infection after the lesion becomes visible to the naked eye, but some will suppress the formation and germination of spores on the established lesion as long as spray residue remains.
The most effective fungicide for apple scab control is not available for home garden use in Australia - it is only available to commercial orchardists. However, you could try a good garden fungicide like Yates Mancozeb. Although Apple Scab is not mentioned on the label, you might find it gives some protection. Apply as directed on the label and don't forget to use personal protective equipment.
