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Apples and other fruits have an odd-looking shape? It is a disease, an extremely contagious one at that: scab. It does not threaten the tree but the harvest is not very appetising! It creates problems on apple trees, pear trees and other fruiting trees.
The symptoms
At harvesting time, a certain number of fruits show signs of brown spots, which have a corky aspect. The skin is deformed around these spots, and even takes on a reddish or orange tint around them. The apple trees on which the fruits are affected also show irregular brown spots on their leaves, symptoms that only confirm the presence of scab.
Lifecycle
Scab is a disease caused by a fungus that manifests itself early on in the year, not long after the opening of the buds. At that time, the mushroom spores (microscopic germs) germinate on the growing leaves as well as on the very young fruits. The mushroom develops on the skin (the epidermis of the fruits and leaves), without causing damage to the rest. This explains why the fruits and the leaves affected by the disease do not fall. The scab disease transmits itself by the dead leaves fallen on the floor that spend all winter around the bottom of the tree. If nothing is done, the disease gets stronger year after year.
How to fight it
When the disease is declared, it is not possible to cure the fruits that are affected. It is necessary to intervene before that stage, as soon as the spring arrives, just after blossoms appear. At this time, a spraying of soluble sulphur, of bouillie Bordelaise solution or any other fungicide product will protect against an attack of scab.
How to avoid it
To stop the propagation of the disease, the best option is to collect dead leaves from the orchard and to put them away to rot down at (at least 100 m away). As this is not always easy to do, a good alternative is to plant apple varieties resisting to the scab disease. A lot of recent varieties do offer that advantage.
Scab is a typical disease found in not well-maintained orchards. Trees that are not well looked after or badly pruned loose vigour and become more vulnerable to diseases of all kinds. As well as scab, it is possible to encounter for example mummified fruits, attacks from woolly aphids and an abundance of lichens. So think about looking after your fruit trees: you will then avoid many problems!
Good to know
Scab is a disease whose virulence has accrued year after year, mainly because of the intensive utilisation of pesticides. Planting a large range of varieties in your orchard (when the space is available) is a good way of avoiding strong attacks. - Photos (1)
Deformed fruits
Deformed fruits
Author: Jean-Michel Groult
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