Ask the Expert: How to handle hornet nests, get rid of webworms
Editor’s note: Throughout the growing season, Mike Hogan, OSU Extension educator for Agriculture and Natural Resources in Franklin County, will answer gardening and home landscape questions submitted by Dispatch readers. Send your questions to [email protected].
Q: There is a large, gray, paper-like hornet or yellowjacket nest hanging from a branch of a tree in our yard that seems to be getting larger, and we see lots of insects entering this nest. How can we remove this nest without getting stung?
A: The nest has likely been constructed by the baldfaced hornet (D. maculata), which are actually black and white yellowjackets, not hornets. At this time of the season, their nests have been enlarged due to the addition of many worker insects which hatched from eggs laid in spring by the queen. The workers have been enlarging the nest all summer, and in late August and September the nest becomes more visible in the landscape.
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Baldfaced hornets are beneficial insects because they feed on many harmful insects in the garden and home landscape. These insects also pollinate flowers that bloom in late summer and early fall. They only become a problem when their nests are located under the eaves of the house or in a tree near a deck, patio, or playground equipment. Even in these locations, when left alone, these insects tend to be fairly benign and even docile. It's only when they sense the need to defend their nest do they become aggressive and repeatedly sting attackers.
For this reason, unless the nest is truly a problem in the yard, we recommend tolerating the nest for now. When the weather turns cooler this fall, the new queen will leave the nest to find a cozy spot to overwinter. The old queen and the workers die when cold weather returns, and the nest is not reused next year. These nests typically fall from their perch during fall and winter weather. If the nest must be removed before cold weather returns, it is best to call a professional pest control firm to remove the nest.
Q: Every year in late summer, insects build web-like nests around the branch tips of several trees in our yard, killing the branches. What can we spray to keep these insects from infesting our trees?
A: Fall webworms (Hyphantria cunea) create the silk webbing and nests which you describe on many different trees and shrubs in the landscape, but they favor black walnut, locust, and cherry species. These insects are pretty much a no-show this season, likely due to higher populations this season of the “3 p’s”: pathogens, predators, and parasitoids, which keep fall webworm populations in check many seasons.
Even when we do see an outbreak of fall webworms, insecticide sprays are rarely effective as it is difficult to get effective coverage of insecticide inside the webbing and tangled foliage in the nest. Preventative sprays are also not recommended as they can also kill beneficial insects such as pollinators. The best control option is to physically remove these nests and crush the insects inside the nest. Even when left untreated, the damage may be unsightly, but has a negligible effect on overall plant health since by late summer and early fall trees have acquired and stored enough carbohydrates through photosynthesis to support next season’s new growth.
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Q: I have drainage issues and poor topsoil in my yard, and I want to spread 8 inches of new topsoil on my lawn and reseed. Is there a problem with adding topsoil around existing trees and shrubs in the yard?
A: There are some potential concerns with adding that much topsoil over the root zone of existing trees and shrubs, particularly mature shade trees. And if your existing drainage issue is caused by compacted soil or a layer of heavy clay soil, simply adding topsoil may or may not completely solve your drainage problem. Adding several inches of new soil above the root zone of trees could “smother” the established roots of trees and interfere with oxygen movement in the root zone.
I would suggest evaluating the grade and slope of the yard to determine if there are low spots where you could add topsoil as a spot application, or if you could add topsoil in certain areas of the yard to the change the grade and thus the surface water drainage of the property.Q: There is a large, gray, paper-like hornet or yellowjacket nest hanging from a branch of a tree in our yard that seems to be getting larger, and we see lots of insects entering this nest. How can we remove this nest without getting stung?Ask the Expert:Q: Every year in late summer, insects build web-like nests around the branch tips of several trees in our yard, killing the branches. What can we spray to keep these insects from infesting our trees?Ask the Expert:Q: I have drainage issues and poor topsoil in my yard, and I want to spread 8 inches of new topsoil on my lawn and reseed. Is there a problem with adding topsoil around existing trees and shrubs in the yard?