March and April are the typical months to notice the activity of ground-nesting bees in turf. Ground nesting bee activity in turf has already begun despite the cool, wet weather this spring. These small solitary bees form a small mound of soil with a pencil-sized entrance hole and their activity sometimes causes concern. Each bee nests singly, but they often are found in aggregations or groups where the turf is thin. Colony-type nesting areas are often located on south facing slopes, but can also occur in flat areas.
There are many species of ground nesting bees, and the date they emerge and become active can vary substantially with the type of bee and the geographic location of the site. Expect more activity as soil temperatures warm and other types of ground-nesting bees emerge.
These bees generally don't sting and present little danger to man. Both the mounds and bees will disappear within a few weeks, and normally do not require control. Chemical treatments are usually not necessary, but there are some options. Nonchemical deterrents include heavy watering, or tilling and heavy mulch in landscape beds.
For more information on ground-nesting bees, please see the TurfFiles publication, Bees in Turf.