[James Kilkelly]

Apple scab on Apple Trees.
by GPI

Plants affected
Apple trees, both edible and crab apple.

Season(s)
Late spring.
Summer

Signs and Symptoms.
Grey-green spots on the leaf surface with blistering often occurring. Leaves will eventually yellow and fall, weakening the tree.

Black-brown scabby spots appear on the fruits skin. This fruit may also be small and misshapen, with some splitting of the skin.
See picture below...
Although the scab infected fruit may be unsightly, scab will not affect the taste and the apples will be still totally edible.

. Apple scab as it appears on leaves and fruit, photo / picture / image.

Cause.
The fungus Venturia inaequalis an overwintering disease, which thrives in wet summers.

Organic or cultural control.
Space trees at recommended distances when planting to promote good air circulation. Your garden centre will advise.

Ensure you have good air circulation around the tree, by cutting back any surrounding planting if practicable.

Collect and destroy all fallen dead leaves that might harbor the fungus.

Whenever you prune established trees, you should leave the centre of the crown open to improve air circulation.

Prune out cracked and scabby shoots during the winter.

Grow only varieties labelled as resistant to Apple scab wherever possible. See list below...

'Discovery'
bright red, crisp, juicy; keeps longer than most earlies. Ornamental tree. Good, regular crops; partial tip bearer; Season: mid Aug.-Sept.

'Lane's Prince Albert'
cooks to brisk purée, not as acidic as 'Bramley's Seedling'. Large fruit. Good, regular crops; fruit easily bruised. Hardy; makes neat small tree. Season: Nov.-Mar.; stores well.

'Laxton's Fortune'
sweet, lightly aromatic flavour; needs to colour well for good quality. Good crops, but tendency to be biennial. Fruit bruises easily, can be poorly coloured. Sept.-Oct.

'Mother'
sweet, perfumed, distinctive flavour. Crops can be erratic, light; Season: Oct .-Dec.

'Ribston Pippin'
intense, rich, aromatic flavour; more acidity and more robust than Cox. Good, regular crops; Season: Oct.-Jan.

'Sunset'
aromatic, like small early Cox, but sharper. Heavy, regular crops, but small fruit. Season: Oct.-Dec.

Other Control.
Spray at bud break with a fungicide containing the systemic active ingredient myclobutanil such as Bayer Garden Systhane Fungus Fighter.

Spray at bud break with the fungicide Captan.

Or else spray at bud break with a fungicide containing the protectant active ingredient mancozeb such as Bio Dithane 945.

Spraying with these fungicides should begin at leaf bud break and continue at approx six intervals, pausing during the trees flowering period, then continuing up to the fruitlet stage in early July.

Associated content...
Powdery Mildew on Apple Trees, Signs, Treat, Control.

Powdery Mildew, How-to Video

How to prune an apple tree without fear.

Prune Apple Trees Between Autumn And Spring, How-to Video

Any queries or comments on Apple scab on Apple Trees, Signs, Treat, Control, please post below.

Images courtesy
Clemson University - USDA Cooperative Extension Slide Series, , United States
www.forestryimages.org