Oak Tree Diseases – Powdery Mildew

mildew_zinnia-269x300Powdery mildew comes from several fungi. They are called Microsphaera alni and Phyllactinia guttata.(Don’t worry – there won’t be a quiz later. We can never remember fungi names either, but they sure make us all sound smart, right?)  Powdery mildew is a very recognizable and common fungal disease. It’s also easily identifiable. Infected leaves have a faint indistinct spot on the upper leaf surface and a white to off-white powdery growth on the lower side. The fungus is often found along the veins and the midribs of a leaf. You will usually notice it in late fall. In severe cases, infected leaves become slightly disfigured.

Powdery mildew is one of the most widespread fungal diseases. From vegetable gardens to rose gardens to oak trees and ornamental bushes, there is almost no tree or plant that is immune to this condition. If you find it on your oak trees, don’t worry. This fungus is host-specific. Just because you find it on one tree, doesn’t mean it is a threat to other trees or plants. There are many different species of powdery mildew. However, they all look the same so we sort of lump them together.

We told you what to look for in the early stages, but what happens in advanced stages of powdery mildew? Well, the leaves can turn yellow, curl or turn brown. This can cause the tree to defoliate, which is not pretty. Powdery mildew likes dry foliage, high humidity, low light, and moderate temperatures. The disease is most severe on trees or plants that are in shaded areas with little to no movement.

While it thrives in humid conditions, powdery mildew does not do well if leaves are wet from frequent rain or irrigation. The most favorable conditions for powdery mildew occur when nighttime temperatures are cool and followed by warm daytime temperatures. Early detection is the best way to eliminate the problem. We suggest that once you notice powdery mildew on your oak trees, that you contact us at Austin Tree Service at 512-341-8888 so that we can help treat the problem. Remember – we don’t diagnose tree diseases, but we can treat tree problems once they are discovered.

Generally speaking, powdery mildew is a mild problem. It does not significantly affect the tree, plant or shrub it is on. It doesn’t really require management. It usually goes away by itself. However, sometimes, because of the condition, photosynthesis can be reduced in the colonized leaves. The best thing to do is to make sure your trees and plants are not overcrowded. You should have us prune your trees regularly to increase light penetration and improve air circulation throughout the canopy. Don’t fertilize if your tree is suffering from powdery mildew. It will just spread the disease.

Sure, powdery mildew may not be a major oak tree disease but many oak trees are affected by it. If your tree suffers from this disease, it’s best to catch it quick and contact us for treatment.