The University of Kentucky Department of Entomology receives several calls a year from growers concerned about ground-nesting or digger bees in their gardens. There are many different species of these bees, and while their sizes can vary, they are generally hairy and dark or metallic in color. Many of these bees are active in early spring and there may be dozens of holes in the ground forming their ‘colony’. I say ‘colony’ but it is not truly a colony, such as those made by honey bees or yellowjackets. These are solitary bees with each female digging her own nest and provisioning her own offspring, but the individual nests are often clustered together. People are sometimes fearful of being attacked by the bees or concerned about the damage they may cause to plants nearby.
Ground-nesting bees prefer to locate their nests where plants or ground cover is sparse, and because of this, they are often blamed for causing the bare area! While it may look like a large colony due to large numbers of entrances, these are independent nests located together (Figure 1). The tunneling activity is not usually damaging to healthy plants or turf, and the risk of being stung is extremely low, as well. These are docile bees that do not defend their nest like social bees and wasps. While the female have the ability to sting if handled, stings are very rare.
With declining wild bee populations, we encourage gardeners to recognize the pollinating service provided by ground-nesting and digger bees. Many of these are specialized pollinators of native plants; others are pollinators of spring crops. Where possible, gardening in harmony with these pollinators is encouraged.
In situations where they interfere with human activity, an insecticide can be applied to burrow entrances to eliminate problem nests. A better long-term solution is to use mulch in bare spots or re-establish ground covers or thick turf to make the area less attractive for nest building.
Ric Bessin, Extension Entomologist