Scab on pear — symptoms and treatment

Severity: medium

What is Scab

Pear scab is caused by the fungus Venturia pirina. It is similar to apple scab but specific to pear trees — close relatives that behave almost identically, though neither infects the other's host. Severity is medium: the tree survives, but a bad year costs you the crop's appearance and its keeping quality, and repeated defoliation gradually weakens the tree.

Symptoms

The first spots appear on the leaves as dark olive-green patches with a velvety, sooty texture and diffuse, feathery edges that blur into the healthy tissue, darkening towards brown or black as they age. Fruit shows the same olive-green to dark spots, which turn scabby and corky. The critical difference on pears is what happens next: scabbed skin cannot expand with the growing fruit, so as the pear swells the rigid patches split. The fruit cracks and deforms — lopsided pears with deep fissures. Heavily infected leaves and young fruit drop prematurely. Twig infections can also occur on pear, which is not the case with apple scab.

• Early signs: dark olive-green, velvety spots with blurred edges on leaves; small dark spots on young fruit
• Advanced signs: scabby corky fruit patches, cracked and deformed pears, premature leaf and fruit drop
• Confusable with: sooty blotch or spray residue — scab lesions are embedded and corky rather than wiping off

Causes and conditions

The fungus overwinters mainly in fallen infected leaves, and on pear also in twig lesions. In spring, spores mature in that overwintered debris and are released into the air during rain, landing on newly emerging leaves and blossoms. This primary wave establishes the disease each year, timed to the tree's most vulnerable stage — the soft, expanding tissue from green tip onwards. Infection needs the leaf to stay wet: the longer the wetness lasts, the more spores succeed. Once lesions form they produce a second kind of spore, splashed by rain onto new leaves and fruit all season, so a wet summer compounds the damage. Crowded canopies and shaded, sheltered sites that dry slowly are the worst affected.

Treatment

Mancozeb + Myclobutanil — chemical

Timing: green tip to petal fall. Apply from green tip to petal fall. Continue at 7-14 day intervals during wet weather. The early window matters most: this is when overwintered spores are released onto tender new growth, and stopping that primary wave prevents the lesions that would otherwise supply spores all summer. These are protective sprays, so they belong on the tree ahead of rain, not after symptoms appear — once the fruit is scabbed, nothing reverses it. Pre-harvest interval: 28 days. Pesticide registrations vary by country — check local approval before use.

Prevention

• Rake up and remove fallen leaves in autumn — they are the source of next spring's spores
• Prune out twig lesions and open the canopy so leaves and fruit dry quickly after rain
• Avoid overhead watering, which extends leaf wetness and triggers infection
• Choose scab-tolerant pear varieties when planting a new tree
• Give trees room and a sunny, airy position rather than a sheltered, shaded corner

Frequently asked questions

Can I eat scabby pears? Yes. Scab affects the skin and the corky layer just beneath — peel or cut it away and the fruit is fine. Cracked pears will not store, so use them soon after picking.

Will it spread to my apple tree? No. Pear scab is specific to pears, and apple scab is a different fungus that stays on apples. Both trees may show scab in the same wet year without either infecting the other.

When should I start spraying? From green tip, before symptoms are visible. The spring infection window on emerging growth decides the season; sprays begun after the spots appear are far less effective.