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Gardening: Brown spots on ash leaves indicate anthracnose

Q. Is this tree dying? If so, I should do something immediately?

— M.K. of Belleville

A. The photos you sent in were excellent. I could tell what species the tree is and what the symptoms are. Your tree is a Green Ash (Fraxinus pennsylvanica). It shows signs of ash anthracnose caused by a fungus disease (Gloeosporium aridum). During wet and humid weather conditions, irregular light brown spots appear on the leaves from May through August. When these sunken reddish areas develop and grow together, they kill the leaves. Partially killed leaves appear to have been sun-scorched. Anthracnose is distinguished by very small dots (spore producing bodies) that are barely visible on the undersides of the leaves. There can be severe leaf defoliation and possibly twig dieback.

This fungus spends the winter on the infected leaves and twigs. During rainy weather, spores are splashed and blown by winds onto young leaves the next spring.

If you look closely, you may notice smaller new leaves developing on some of the affected branches.

Usually this disease does not require any control the first year you notice the problem. But you should prune off any of the affected leaves and small branches. Make sure you use rubbing alcohol or bleach to clean your pruners after each cut is made. You will also need to rake up and get rid of any diseased leaves and branches through the end of this year.

Fertilize the tree early next spring to stimulate new growth.

Also, if we have another wet spring, you will need to spray the entire tree with the fungicide containing benlate or captan when the leaves begin to break bud. Repeat this spray treatment at least two times at the interval of 14 days.

There are other species of spot anthracnose that attack trees but they usually do not kill the tree but infect flower blooms on dogwood, linden and pecan.

Q. How does one know when to harvest winter squash? I have asked some gardeners and I cannot get a good answer?

— N. B. of O’Fallon

A. Winter squash usually ripens in late August and September. There are several different types of winter squash and each has its own ripening characteristics, which pertain to color. Butternut squash changes from light beige to a deep tan color when ripe. Acorn squash has a deep glossy green rind that develops a yellow spot where it faces the soil. When the spot turns orange, it is ripe. Spaghetti squash changes from creamy white to a bright yellow. The delicata squash has green streaks across a white background. This squash is ready when the white changes to beige and an orange blush appears.

Do it now: You can plant grass seed to redo the whole yard or to fill in bare spots beginning right now until the middle of October.

Charles Giedeman is a local contributing writer. Send your gardening questions to Lifestyle Editor Patrick Kuhl, Belleville News-Democrat, P.O. Box 427, 120 S. Illinois St., Belleville, IL 62222-0427, or email them to pkuhl@bnd.com.

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