Silver leaf

Silver leaf occurs mainly in apples and stone fruit in all growing regions but is particularly common in areas with high humidity during the growing season. It is caused by the Chondrostereum purpureum fungus.

Disease identification

The foliage of infected trees will develop a silvery sheen that is caused by light shining through leaf cells that are damaged by toxins produced by the fungus.

Damage

Overall tree health declines, with reduced leaf area, poor root growth and low yields of poor-quality fruit that does not store well. In storage, infected fruit is susceptible to decay caused by other secondary infections.

Apple trees tolerate the disease better than stone fruit trees, which often die. The disease can lead to an increased incidence of water core in apples.

Monitoring

The peak risk period for silver leaf is from postharvest through to mid-season. Damp, overcast conditions can increase the incidence of silver leaf in orchards. Particular attention to pruning wounds when these conditions are present is recommended. Other forms of wound sites, such as from hail, could create infection sites for silver leaf and should be monitored regularly.

Management

Cultural and physical: silver leaf can be controlled by careful pruning and using wound dressings. Winter pruning should be avoided, particularly on damp, overcast days. Apply wound dressings as soon as possible after pruning and grafting to avoid infection.

Biological: there are currently no biological control options for this disease.

Chemical: check the APVMA PubCRIS database for registered controls (https://portal.apvma.gov.au/pubcris).