Gardening: How to treat hollyhocks stricken with blight

For the News-DemocratJuly 11, 2013 

Q. My common hollyhocks seemed to develop a blight early this summer. At least, that's my assessment since the leaves are turning brown and drying up. These single-layer blooms have been blooming for a couple of weeks but will soon be done. I had a number of hollyhocks growing in several locations for some years and the last couple of years had this problem. I remember many years ago out in the country them blooming and blooming well into summer. Why did mine get blight?

-- G. C. of Belleville

A. Hollyhocks (Althaea officinalis) are bothered in the Midwest by a blight you correctly identified. It's commonly known as hollyhock leaf spot (Cercospora althaeina). When this disease starts, there are circular spots that may become irregular shapes in time. The dead part usually falls out and eventually the whole leaf dies.

The blight can start as early when the hollyhocks are about six weeks old. This starts with early spring moist weather conditions. The disease speeds up when the weather turns warm, spores form and they are carried in the wind or splashed by rain. This part of the life cycle of the disease can be completed in two weeks. As long as the weather has there are rains, the disease can spread.

In last year's drought, the disease should not have been as bad as this year.

There are two controls to prevent the disease. Pull out the old plants in the fall as spores will overwinter in plant parts. You can save seeds from these plants to grow them again, but first place them in hot water (118 degrees) for 30 minutes to kill the spores. This temperature will not hurt the plant embryo inside the seed.

One variety of hollyhocks, Emerson Pascal, is resistant to this disease. I have had a hard time trying to locate the plants and the seed.

Q. Something is eating the leaves on my grapes, roses, crabapple trees, and even my cherry trees. The leaves end up with most of the leaf eaten or they have some of the veins of the leaf remaining. This seemed to happen overnight in the last 10days. On occasion I have found a small green colored beetle on some of the leaves. What is it and how do I control it?

-- K. M. of Mascoutah

A. The Japanese beetles have landed. They emerged from the soil in June and began feeding on the lower growing plants and working their way up to the tree leaves. These adults can live from 40 to 45 days and are most abundant during July. Just before they die, the females mate and lay eggs, primarily in lawns. The larvae hatch out, then devour the lawn areas until the weather turns cold and the soil begins to freeze.

Many different insecticides kill them. Read the label to make sure. There are different insecticides for killing the Japanese grubs in the turfgrass and for killing the adults feeding on the leaves.

Lemon juice (7 tablespoons) added to a gallon of water with a tablespoon of liquid dishwater detergent as a sticker will prevent damage on your prize plants if you act soon enough.

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

Do it now

DELPHINIUMS: Cut back plants when they have finished blooming. This will encourage a later bloom in late summer or fall.

POPPIES: Divide and transplant when they have finished blooming.

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