There are many common species of solitary bees that nest in individual holes in the ground. They are all good pollinators. These bees range in size form 1/2 to 3/4 inches and may be a variety of colors such as blue, green, copper or metallic reddish-brown. They may belong to one of several groups of bees such as the membrane bees, digger bees, sweat bees, mason bees and leafcutter bees (Colletidae, Halictidae, Andrenidae, Anthophoridae, Megachilidae) and occur across the state. During the evening hours, females excavate nesting burrows that reach six or more inches in depth. Some of these bees line the burrow with a water-proofing secretion for protection from moisture. Small mounds of excavated soil may appear around each nest opening. When bees are numerous, many holes may be in closed proximity, creating a "citylike" aggregation. Each hole belongs to an individual female. During the day, the active females collect pollen and nectar to carry back to the nest to form a "ball" 1/8 to 14 inch in diameter that is placed within a "cell" excavated in the side of the burrow. A single egg is laid upon the pollen ball in March, April or early May. After hatching, the larva feeds on pollen and develops within the cell into a new generation of bees. The new generation emerges the following year in March or April. At this time, mating takes place and bee activity begins to pick up as the nesting cycle resumes. Though adult bees feed on nectar, none store honey as such. Solitary, ground nesting bees play a vital role in ecological systems, especially in pollination of crops and wild plants. Solitary bees are valuable pollinators and should not be destroyed unless there is some compelling reason.
Cultural control methods include heavy watering or irrigation with a lawn sprinkler during the nest-building period to discourage nesting. Tilling of soil to destroy tunnels may help a little, but establishment of dense turf is probably the best discouragement to further nesting. Applications of heavy organic matter could be included as a soil amendment, if practical, when tilling the soil. If the soil or location is not conducive to a healthy lawn, using ground covers or heavy mulches may be an alternative solution. Mulches may be used on bare patches caused by heavy traffic where grass will not grow.
If chemical treatment is desired, recommendations for insecticides approved for control of these insects in home lawns can be found under Bees and Wasps in INSECT CONTROL IN HOME LAWNS in the NC Agricultural Chemicals Manual. Recommendations for insecticides approved for use on sod farms, golf courses or other commercial sites can be found in COMMERCIAL TURF INSECT CONTROL in the NC Agricultural Chemicals Manual.
For additional information on insect control and pesticide use, contact your county Cooperative Extension Center.