Ground Nesting Bees: Are they a threat to you-or your Lawn?

Updated May 2016

Spring brings the return of the birds and the bees to our yards and gardens.  While the sound of birdsong may be a pleasant herald of spring, many people are less happy about the reappearance of wasps and bees to their garden.  In particular, the ground nesting bees that increase their activity in many lawns in early spring can alarm many people; particularly when their "dirt pile" nests start appearing in the lawn.

Ground nesting bees look very much like this honeybee.

Colletes inaequalis, one of many types of ground nesting bee. They are very similar in appearance to honeybees.

Ground nesting or miner bees are solitary bees that create underground galleries, with queens living individually and raising their own young.  The entrances to the nests are small piles or patches of bare soil.  They do not form hives, but several females may nest in the same area.  Ground bee queens do not defend their nesting areas and are very docile and unlikely to sting, posing little or no threat to people.  The males often patrol an area inhabited by females seeking mates.  While the males can be very active and seem aggressive, they lack a sting and are also harmless.  Like other bees, they are active foragers of nectar and pollen from flowers, making them beneficial pollinators.

Their nest entrances are small mounds of soil a few inches across.  While they may briefly detract from the aesthetics of a well-tended lawn, they do absolutely no harm to the grass or soil—even improving it as their nests function as aeration holes, improving the penetration of water and nutrients.  Eventually, as the nests are abandoned after the spring nesting season, the soil washes back into place with rain, disappearing completely.   

These are NOT docile ground nesting bees, they are yellow-jackets and are bad tempered and aggressive.  Do not confuse them with docile ground nesting bees or you will have a very bad day.

These are NOT docile ground nesting bees, they are yellow-jackets and are bad tempered and aggressive.  Do not confuse them with docile ground nesting bees or you will have a very bad day.

If you feel you must get rid of ground bees even for the brief time they live in your lawn, there is no need to use pesticides of any kind.  Ground bees prefer dry soil to nest in, and simply watering the area that they have chosen will cause them to move to another area. If you find ground nesting bees return to your lawn in large numbers year after year, run a sprinkler on the area before they show up; ground nesting bees prefer dry soil to wet soil and will look elsewhere to make their nests. (Make sure that you are evicting ground bees and not yellow-jackets. Yellow-jackets reaction to a water eviction will not be “non-aggressive” by any means.  A yellow jacket nest will look like a busy airport with many insects entering and leaving in a constant stream, and entrances can be well over an inch wide.  Only one ground bee will be seen leaving and entering a hole only about ¼” wide.)

Even better, leave the ground bees to go about their business-they won’t be around long, and will even benefit your lawn and garden while they’re visiting.  Just like robins, they’re another welcome sign of spring.

Photo Credits
Colletes inaequalis: By USGS Native Bee Inventory and Monitoring Laboratory [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
All others bigstock.com

Other articles on our blog about "bees":

Cicada Killer Wasps       Leaf Cutter Bees