Velvety spots creep over the leaves, then brown patches surface on the fruit and rot the flesh as they spread: that is scab, a fungal disease whose spores overwinter on fallen leaves. Pear and apple trees suffer worst, so clear those leaves and the following spring stays clean.
Advice on keeping it from appearing and getting rid of it.
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Although it also infects medlar and plum, it is most famous for infecting pear tree and apple tree for which scab is known to provoke devastation. Fruits on infected trees start showing brown spots that make the fruit rot as they spread across the flesh.
Spores from a fungus that overwintered on dead leaves are responsible for this contamination. First, the tree’s leaves are covered with velvety spots during the primary infection.
Things can stop there, but if it is a rainy summer, spores propagated by the spots on the leaves will germinate on the flowers and fruits of the tree. This is called secondary infection.
In regions with rainy springs and summers, the variety you plant matters as much as the treatments you apply. The article’s picks fall neatly into two camps.
| Variety | Fruit tree | Type | Behaviour with scab |
|---|---|---|---|
| ‘Belle de Boskoop’ | Apple | Heirloom | Resists scab |
| ‘Reinette du Mans’ | Apple | Heirloom | Resists scab |
| ‘Reinette des Flandres’ | Apple | Heirloom | Resists scab |
| ‘Ariane’ | Apple | Recent breeding | Developed specifically to resist scab |
| ‘Conference’ | Pear | Heirloom | Resists scab |
| ‘Williams’ | Pear | Heirloom | Resists scab |
| ‘Golden’ | Apple | Common commercial | Particularly sensitive |
| ‘Orange Cox’ | Apple | Common commercial | Particularly sensitive |
| ‘Beurré Hardy’ | Pear | Common commercial | Particularly sensitive, as are its hybrids |
| ‘Beurré Giffard’ | Pear | Common commercial | Particularly sensitive, as are its hybrids |
Whichever you lean towards, ask your local horticulturist about scab before buying the tree.
In case of contamination, it will be difficult for you to save the current harvest, but a few good practices will help you eliminate any risk of a new infection in the following spring.
Scab is expected to appear in regions with rainy springs and summers. In those areas, best is to choose heirloom varieties that have learned how to resist scab: ‘Belle de Belle de Boskoop’, ‘Reinettes du Mans’ or ‘Reinette des Flandres’ for apples; and ‘Conference’ or ‘Williams’ for pears. Certain recent varieties such as ‘Ariane’ for apples have been developed to resist it.
Oppositely, varieties such as the ‘Golden’ or the ‘Orange Cox’ for the apples, and ‘Beurré Hardy’ or ‘Beurré Giffard’ for pears and their hybrids are particularly sensitive to scab.
Ask your local horticulturist about scab when buying your fruit tree.
Laure Hamann
