This disease most often occurs in deciduous trees and shrubs. Apple scab is the most famous of its varieties, and in the case of ornamental plants, scab scab.
Apple scab
It is considered the most dangerous disease of these trees. It is caused by the fungus Venturia inaequalis. The first symptoms of scab are visible on the leaves in the form of velvety, olive-green, with time, darker and darker spots of various sizes. Heavily infested leaves dry up and fall off. Then the spots appear on the fruit.Initially, they are velvety, then a layer of cork tissue, visible as black, dry scabs, forms at the site of damage. The fruit often bursts. The disease appears in warm and humid summers. Its development is severely restricted when it is dry. Optimal conditions for scab are 17-24 ° C and light rainfall lasting more than 9-18 hours.
Prevention of this disease is difficult and requires consistency in action. The protection of trees begins in the fall, after the fruit is harvested. The leaves should be sprayed with a 5% urea solution. This will cause their decomposition faster and destroy the fungus wintering there. Fallen leaves must be collected and burned. It is also important to prune the trees. A loose and thinning crown will allow air to flow more freely, which will cause the leaves to dry out faster and destroy pathogens.
Another way to combat scab is to grow apple varieties resistant to this disease, e.g. 'Liberty', 'Novamae', 'Freedom', 'Primula', 'Prima', 'Priam', 'Florina'.
In the case of apple scab, it is not recommended to perform chemical treatments in allotments and home gardens, because there are too many factors responsible for the occurrence of this disease and the need to spray trees repeatedly during the entire growing season, at carefully selected dates.
Scab of other fruit trees
This disease also affects peaches (Cladosporium carpophilum fungus), pears (Venturia pirina fungus) and cherries (Venturia cerasi fungus). The methods of preventing scab in these trees are similar to that of apple trees and consist mainly of non-chemical treatments. You should also remember to remove infected fruit and collect fallen leaves. In the case of peach scab, the entire infected shoots must be removed, because this type of fungus overwintering there.
Scarlet fire scab
It is the most dangerous disease of this ornamental shrub caused by the fungus Spilocaea pyracanthae.The first symptoms are observed in the fall. Olive-colored spots with clearly marked margins appear on the underside and sometimes the upper side of the leaves. As the disease develops, they merge with each other, covering almost the entire surface of the leaves. The tissues around the spots turn yellow and the leaves fall off. In late autumn, brown spots appear on the fruit. Their surface is cracked and they dry quickly. Fallen leaves and fruit must be removed and burned. Frequent rainfall and very high air humidity contribute to infection. Avoid soaking the shoots and leaves when watering the shrubs.
In the case of fireworm, Baycor 300 EC can be used after the first symptoms of scab are noticed.
