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Trouble with ash trees?

You're looking out your picture window at your towering ash tree that you have come to love. There is no breeze but yet the leaves could not be falling faster.

Seeing leaves fall in the spring is always an alarming sight. With further examination, you see brown spots on the leaves.

The recent outbreak of emerald ash borer in Minnesota has some ash tree owners in a nervous state. While EAB might be a problem, ash anthracnose may be the real criminal in the recent leaf drop.

Emerald ash borer may be your first thought as you watch the leaves fall, but before you take any drastic measures, you might want to take a closer look.

With EAB, the canopy of the tree will appear thin, with few to no leaves at all. Amongst this bareness, you may also notice dead branches.

Cracks and D-shaped holes in the bark are found on the trunks of contaminated trees. Woodpeckers are also a common visitor on trees with EAB larvae. After fully developed, EAB becomes a half-inch long green beetle.

On the flip side, ash anthracnose will appear to have dark brown or black water-soaked spots on the leaves and young shoots. Leaves can be seen as distorted or curled around the infected area.

As the petioles and shoots become infected, the leaves will drop. Ash anthracnose is most severe in the lower and inner branches.

This fungal infection is very common in cool, wet spring weather but will not persist in warm, dry summer weather. Mature ash leaves are resistant to the fungus.

As the weather turns warm and dry, tree leaves will mature and ash anthracnose will not be able to spread. Leaf replacement will be seen midsummer.

If you find yourself with the infestation, fear not. Ash anthracnose is considered a minor stress to the tree's life.

Simple activities like watering trees during periods of drought, mulching the soil at the base of the tree to reduce competition with turf grass and avoiding wounding trees with lawn equipment will help the tree recover its strength.

Raking up and removing infected leaves at the end of the growing season will help to reduce the amount of fungi that survive from one season to the next.

For more information, visit the University of Minnesota Extension Yard and Garden news blog at