Q: I planted an Autumn Blaze Maple about three years ago and it looked great until this year. The tree has been very yellow all summer. Can you tell me what the issue is and how I can resolve it? — Dean J., Fargo.
A: Your Autumn Blaze maple has a severe case of chlorosis, a yellowing most commonly caused by a tree's inability to access iron, and sometimes magnesium, from the soil. Early symptoms begin with veins remaining green, while the leaf areas between veins turn yellow. As the disorder becomes severe, leaves turn lemon-yellow and develop black areas of dead leaf tissue.
Iron deficiency chlorosis is a common disorder of maples in the heavy clay, alkaline soil of the Red River Valley. Most maples are better adapted to the naturally forested soil of Minnesota and eastward.
To remedy the problem, apply a form of iron readily absorbable by the tree, called chelated iron, available at garden centers. Foliar sprays of iron are faster-acting, but not long-lasting. Soil applications, absorbed by tree roots, act slower, but last longer. Combining a foliar spray with a soil application is often a successful approach. Follow label for timing and mixing instructions.
Nursing a maple out of severe chlorosis can be an uphill battle, which often requires continued applications of chelated iron.
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Q: This is our first year with a Honeycrisp apple tree. When should the apples be harvested, and how do you know they’re ready? — Michelle N.
A: Some apple varieties ripen in August, some in September and some in October, which is fairly consistent from year to year. Honeycrisp generally ripens about Sept. 20 through early October. It's important to harvest apples when they are fully ripe, or the quality won't be as high and the storage life will be reduced.
Besides the general ripening date of Honeycrisp, there are other ways to tell if an apple variety is ready for harvest. The background, non-red color turns from green to creamy yellow on many varieties, apples begin detaching themselves from the tree, the seeds turn from tan to black-brown and the flavor becomes pleasant, rather than sour.
Q: I have a wasp nest in the wall of my house. There is a gap where the gas pipe leads in and they’ve made it their new home. I’ve sprayed several times but can't get the stuff inside. Should I just plug the hole? — Dave Waale.
A: First, our natural inclination is to plug the hole, but this can be dangerous. These insects are often able to create tunnels, and if the outside opening is blocked, they might find their way into the interior of the home, presenting an even more dangerous situation.
Using a spray insecticide for wasps and hornets, wait until just before dark, which is when most of the wasps will be inside the nest. For extra precaution, protect yourself with long sleeves, gloves and long pants. Then get as close as you feel comfortable, and spray as much of the insecticide into the opening as you can.
If that doesn't give complete control, try to load Sevin dust into the gap so the insects contact the insecticide as they enter and leave. Sevin is quite effective, but doesn’t have the fast knockdown of the aerosol wasp and hornet killers. When no activity is present, the opening can be sealed with caulking or foam sealant to prevent future nest building.
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ARCHIVE: Read more of Don Kinzler's Fielding Questions columns
If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at donald.kinzler@ndsu.edu or call 701-241-5707. Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.
