apple scab

Symptoms

Olive-green to black velvety spots on leaves, similar dark sunken scab on fruit causing cracks, premature leaf and fruit drop, weakened tree over years.

Plants affected

• apple

Easily confused with

• apple powdery mildew

  How to tell them apart: Apple scab (Venturia inaequalis): olive-green to black velvety blotches with diffuse edges on leaves, and corky brown scabs that crack the fruit, worst after wet springs. Apple powdery mildew (Podosphaera leucotricha): white felty coating on shoot tips and young leaves that stunts, silvers and curls them, and can leave a russet net on fruit.

• European pear-juniper rust

  How to tell them apart: Apple scab (Venturia inaequalis): dark olive-green to black velvety leaf spots and fruit scabs, no orange colour. Apple/juniper rust (Gymnosporangium tremelloides): BRIGHT orange-yellow rounded spots on the upper leaf, often with small tube- or cup-like structures protruding from the underside, and it needs nearby junipers to complete its cycle.

• apple blotch

  How to tell them apart: Apple scab (Venturia inaequalis) starts as olive-green, fuzzy, velvety spots with diffuse, feathery margins on the upper leaf surface, often along veins; lesions later turn dark brown to black, corky and may distort the leaf, and matching scabby cracked lesions appear on the fruit. Marssonina blotch (Marssonina coronaria) instead produces distinct dark brown to greyish-green rounded blotches with a fine green-yellow halo or mottling between the dark spots; tiny black fruiting dots (acervuli) form in the centre, leaves rapidly turn yellow and drop from mid-summer, usually with little or no scabbing on the fruit. Scab favours cool wet spring weather, whereas Marssonina blotch peaks in warm humid mid-to-late summer.

Common questions

How do I recognise apple scab on apple?

Olive-green to black velvety spots on leaves, similar dark sunken scab on fruit causing cracks, premature leaf and fruit drop, weakened tree over years.

Do I have to report apple scab?

No. apple scab is not a notifiable organism, so there is nothing to report to an authority. Treat it as a normal garden problem.

How is apple scab treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.