Question: I am having quite a time with bees in my lawn. They are boring into the ground and I can see all the holes. They are just making piles of sand. I am really beside myself and do not know how to get rid of them as there are a lot of them. Any advice?
Answer: Unlike the social bees we see living in colonies; solitary bees build their nests in burrows in the ground. They belong to one of several groups including mining or digger bees, sweat bees, mason bees and leafcutter bees. Bee populations can vary dramatically from one season to another.
During the evening, females excavate nesting burrows that reach down into the soil six or more inches. Some bees line their burrow with a water-proofing secretion to help provide protection from moisture. In the process of building their burrow, the excavated soil will be pushed out creating a mound at the opening. When there are large numbers of ground-dwelling bees many holes are in close proximity and appear as a colony. Each hole belongs to a single female.
In the daytime the female is out gathering pollen and nectar to carry back to the nest in the form of a ball 1/8- to 1/4-inch in diameter. Each ball is placed in a cell created in the sides of the burrow. A single egg is then laid on the pollen ball in April or early May. When the egg hatches, the larva begins to feed on the pollen where it continues to grow in the cell. The next spring or early summer the new generation emerges and mating, as well as nest formation, begins.
Bees that make their nests in the ground prefer areas that receive morning sun as well as well draining soils that are low on organic matter. They usually avoid areas with dense vegetation and remain damp. When they appear in the lawn they usually cause minimal damage and control is not warranted. These solitary bees are not stinging bees unless they are handled or become trapped in clothing.
It is important to realize these bees play an important role in ecological systems, particularly pollination of crops and wild plants. As a valuable pollinator they should not be destroyed unless there is a very compelling reason. When control methods are necessary cultural ones are recommended. In areas where there is a lawn, irrigation with a sprinkler will discourage nesting. Where there is no lawn growing, tilling in heavy organic matter, using a groundcover, or heavy mulch also can be successful in deterring their burrowing.
Mona Bawgus is a certified master gardener and consumer horticulturist with Rutgers Cooperative Extension of Atlantic County. Write to her c/o Rutgers Cooperative Extension, 6260 Old Harding Highway, Mays Landing, NJ 08330. Email: