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Cathy Peck/Master Gardener: Avoid apple problems through sanitation

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Cathy Peck/Master Gardener: Avoid apple problems through sanitation
Bemidji Minnesota P.O. Box 455 56619

Two problems commonly associated with apple trees plague growers: apple scab and apple maggots. It is too late for remedial action at this time of year, but what you do now can affect next year's crop.

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Scab, a fungal disease infects leaves and fruit. Tree leaf lesions start as olive green spots that turn brown and grow to merge together. The leaves often turn yellow and drop early. Lesions on the fruit that start as tiny olive green to brown spots grow and harden, creating black and corky, inedible spots. Fruits can even become misshapen and crack.

This disease winters over on fallen leaves infected with the disease. In spring spores shoot out, infecting new leaves; the disease cycle starts again. Abundant rainfall in May and early June increases disease severity.

This disease does not only affect the apples we eat but also ornamental crabs so when purchasing new apple trees, look for ones that are resistant to this disease.

A second problem affecting apple varieties is the apple maggot. These creatures disfigure the fruits with what begins as a small brown spot where the fly lays its egg under the skin. This then progresses to a dimple. A maggot hatches and feeds for a month, creating brown streaks and allowing for disease organisms to enter. The fruits are edible but definitely have that "ish" factor! Apples not picked often fall to the ground.

Then the maggots emerge and overwinter in the soil until in spring, they emerge as small flies. The flies feed, mate, and lay eggs just under the apple skin. Each female can lay more than 300 eggs. It doesn't take a math genius to recognize how much fruit can be affected. Traps and sprays are effective in controlling apple maggots but it is too late in the year for that now.

What you do now and until the snow flies can prevent scab and apple maggot problems. It just like what we teach our children: clean up continually so there doesn't get to be an insurmountable mess. Harvest all the apples you can. Then, keep the area under apple trees clear of fallen apples and leaves. Cleaning up the apples as they drop will prevent the maggots from entering the soil. Also pick any apples left on the tree to avoid disease or insects from overwintering in the fruit.

Keeping the area policed from rotting apples will also keep pesky wasps and hornets from setting up housekeeping in the fallen fruit. It is never pleasant to hear that telltale buzz warning you to stay away. Seeing a child or pet get stung is worse than being stung yourself. Folks with allergies can be endangered as well.

Second, remove fallen leaves, broken branches or prunings until the snow flies. Take it away from the orchard to avoid the problem of disease organisms and insects from re-infecting next year's crop and leaves.

Last year a bear helped us with apple cleanup. A short trip to Iowa interrupted our apple picking then those lovely golden apples were at their prime. Their intoxicating scent brought in a local bear. He or she enjoyed the apples but destroyed half of the tree in the process. This was not the way to avoid the apple maggot problem and it surely created a lot of pruning debris and leaves to haul away.

To find reliable information about vegetable gardening and other horticultural topics, go to the University of Minnesota Extension website at www.extension.umn.edu/gardeninfo Local master gardeners will also answer your gardening questions via a voice-mail service. Call 444-7916, leaving your phone number, name and the nature of your question. A volunteer master gardener will give you a call.

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