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How to deal with the yearly fall nuisance of yellowjackets

Its best to treat yellowjackets at night.1 / 2
Don Kinzler, Growing Together gardening columnist for The ForumMichael Vosburg / Forum Photo Editor2 / 2

Q: I'm being attacked by yellowjacket wasps every time I step out my door. I've set out traps that work especially well but have not found a hive. The trap uses a homemade recipe containing six ounces of vinegar, two tablespoons sugar and one teaspoon salt. I've emptied the trap several times, but there seems to be an unending amount. I'm concerned that they're attacking our huge apple crop. - Laura, Glyndon, Minn.

A: North Dakota State University has the following recommendations: "Populations are soaring now—a single nest may contain thousands of yellowjackets. These pests can sting several times and some species will sting even when unprovoked. Yellowjacket nests in an out-of-the-way area are usually best left alone. The pests will die after a hard frost. If the nest is concealed (for example, under siding or in a wall void), shoot insecticide dust (Sevin or permethrin) inside the hole using a turkey baster. Do not seal the entrance; otherwise they will create a new hole which may be more hazardous. If the nest is in the ground, sprinkle insecticide dust into the hole. Treat at night, when all yellowjackets will be in the nest. If activity continues the next day, treat again. Yellowjacket traps help but capture only a small percentage of the pests."

Thanks, Laura, for sending the recipe for the trap.

Q: What is your opinion of aerating lawns in south Fargo, and how often should it be done?—Dale Weber, Fargo.

A: Core aeration is especially beneficial for lawns with heavy clay soil. Aeration opens up the lawn structure, letting air, water and fertilizer penetrate more readily. Soil in new developments is often heavily compacted by equipment during home construction. Core aeration, where plugs of soil and thatch are lifted out, is more effective in alleviating compaction than power-raking, which is mainly for thatch reduction. There's not a hard-and-fast rule about core aeration frequency, but every four years should be often enough, maybe sooner on highly compacted sites, and September is a great month for it.

Better tree mulch dimensions

In the past, I've written about the 3-3-3 method of mulching around trees by placing wood mulch in a three-foot diameter circle, three inches deep and kept three inches away from the trunk.

Neal Holland, long-time NDSU professor of horticulture and longtime owner of Sheyenne Gardens, Harwood, has a better recommendation. He favors increasing the dimensions to 5-5-5: wood mulch in a five-foot diameter circle, five inches deep and kept five inches away from the trunk.

Neal echoed the importance of keeping grass away from the rootzone of young trees, as grass produces soil substances that diminish the growth of plants with which it competes. I've learned a great deal from Neal Holland, first as a student of his in NDSU horticulture and also in the 40 years since, and I have great respect for his knowledge and views.

The increased mulch dimensions make sense, giving greater protection to a young tree's root zone. From now on, you'll hear me advocating a 5-5-5 mulch ring.

If you have a gardening or lawn care question, email Don Kinzler at All questions will be answered, and those with broad appeal may be published, so please include your name, city and state for appropriate advice.