In early spring, gardeners contact Clemson Extension offices and the Home and Garden Information Center frantically describing bees digging holes in the lawn, swarming their grass, and damaging the turf.
There’s no need for panic. I’ll explain.
Adult emerging from its burrow.
Ward Strong, BC Ministry of Forests, Bugwood.org
What Are Those Holes in the Lawn?
The holes measure approximately .25 inches in diameter and may or may not have dirt piled around them. If one watches the holes closely, one might observe a bee coming and going from the holes. Upon closer inspection, one will see more bees flying a few inches above the ground, and they appear to be patrolling the area where the holes are. The holes and accompanying bees are concentrated in warm, sunny, dry areas of the landscape with well-drained soils that are low in organic matter.
Meet the Ground-Nesting Bees
These are likely ground-nesting bees, some of the first bees to emerge as the weather warms up in the spring. The adults are active for only a few weeks.
There are several families of ground-nesting bees with the bees varying in size, color, and nesting locations depending on the species.
Are Ground-Nesting Bees Dangerous?
The bees are not aggressive, nor are they defensive of their nests. Although the female bees can sting, they tend not to unless provoked or handled roughly. Therefore, these bees are not considered a significant medical threat to most individuals. For the most part, people and pets can continue outdoor activities without worrying about being stung by ground-nesting bees.
Burrow entrance of an Andrenid bee (Genus Andrena).
Whitney Cranshaw, Colorado State University, Bugwood.org
Understanding Their Nesting Behavior
Unlike honey bees, these bees are primarily solitary but colonial and gregarious. Each individual female ground-nesting bee builds her own nesting burrow. According to NC State Extension, “During the day, females collect pollen and nectar to carry back to the nest and form a 1/8 to ¼ in diameter “ball” that is placed within a small cell created in the side of the burrow. Females lay a single egg on the pollen ball and when it hatches, the larva feeds on the pollen and continues to develop throughout the year. The new generation will emerge the following year in the spring.”
Do Ground-Nesting Bees Damage Lawns?
Homeowners frequently blame the nesting activity of ground-nesting bees for thinning turf. However, more often than not, unfavorable or poor growing conditions are the actual contributing factors for the weak turf, and the bees are simply locating their nests in their preferred environment.
How to Discourage Nesting in the Future
Ground-nesting bees are beneficial insects that serve as essential pollinators in our landscapes. Because these bees are valuable and only a temporary nuisance, we do not recommend chemical treatment (insecticides). To discourage nesting activity in the future, improve growing conditions that support thick, dense stands of turf. If the soil or growing conditions are not conducive for thick stands of turf, homeowners might consider installing a groundcover or mulching the area. For more information, see HGIC 1100, Groundcovers: Planting and Care and HGIC 1604, Mulch.
Let them Bee- For a Healthy Ecosystem
Although this fact sheet is from Michigan State University (https://www.canr.msu.edu/news/solitary_bees_in_yards), the information is very good and applies to our South Carolina landscapes.
The emergence of ground-nesting bees is a spiffy indicator that spring is here. I hope homeowners and gardeners will tolerate their short-lived activity in the landscape for the sake of ecosystem health.
