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Pear Scab

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Caused By:-     The fungus Ventura pirina

Description

Pear scab is most prevalent in mild, damp seasons. It is caused by the fungus Ventura pirina which is closely related to the apple scab fungus Venturia inaequalis. The fungus overwinters on fallen leaves in the form of spores, which can be splashed by rain or carried in the wind to infect newly emerged shoots in spring. Overwintering can also occur on infected stems and branches. The most serious consequence of scab is reduced vigour of the trees caused by early leaf fall. This may limit the crop of fruit. The disease also causes scabs on the skins of fruit, although they are still edible.
The symptoms are black blotchy patches on pear foliage, fruit tends to be undersized and exhibits the same blotchiness and as it grows these harden and often crack. Put simply, the fruit looks "scabby".
In the spring scab spores settle on the tree where they germinate, grow and release more spores in early April and again and again at intervals every few weeks. The disease thereofre appears to be progressive, when it is in fact caused by waves of infection.
Spores germinate and infect if the leaf surface when it is wet for long periods. The fungus grows best in relatively humid conditions. Consequently the disease develops mainly during mild wet seasons. See also APPLE SCAB.
Howard F. Schwartz, Colorado State University, Bugwood.org.

Control

Good husbandry is essential in preventing this disease. Therefore rake up fallen leaves at the end of the growing season and dispose of them - don't add them to your compost heap if they came from a tree with this disease. Prune damaged stems and crowded branches. Liaise with neighbours who have fruit trees to make sure they practise similar hygiene.
Some varieties show some scab-resistance and plant trees in open, sunny positions and keep the center of the tree open to allow airflow.
As soon as the leaves emerge until late July, spray plants regularly with a fungicide
Feeding is important as well planted that are mulched with good, well rotted organic matter in the spring grow stronger and more resistant than underfed ones.
A winter tar wash and spraying with fungicide will help to limit the damage caused by this fungus.

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