Arbor-wellness: Leaf Scab

Leaf Scab becoming a problem again.

Leaf scab diseases are a type of fungal infection that affect the leaves of apple, hawthorn and crabapple trees primarily. There is more than one fungal organism that creates this disease, but how they attack a tree and the treatments for them are very similar, so we will simplify the discussion by calling them leaf scab diseases.

Apples, crabapples, and hawthorn all can be affected by this disease, as well as some pear tree types. Out breaks are more severe after a wet, cool spring.

The fungus develops in the early Spring after spores are produced and distributed by wind and rain.

These spores infect newly forming leaves causing small brownish-green lesions on the young leaves. Once established on the new leaves, new spores are form and the process is repeated. As the disease develops on the leaves, the infected areas change colors and spread, until most of the leaf is affected and it falls off. Fruit can be affected too and even flowers may show symptoms. The fruit will become deformed and fall off prematurely.

Some varieties of flowering fruit trees are resistant and it is important when planting new ornamental hawthorn, crabapples or pear that you select the right varieties.

Older varieties are often most susceptible and need regular treatments to prevent early leaf fall. While it typically doesn’t kill the tree outright, the lack of leaves reduces the health and vigor of the tree and makes it more susceptible to other problems.

Arborwell has successful and cost-effective preventative programs available as well as “rescue” type programs that may be needed in certain situations.

Your Arborwell arborist can determine if this is a problem in your landscape and recommend an appropriate program for you.

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