Andrena

Andrena is a genus of solitary bees within the family Andrenidae, order Hymenoptera. Unlike social bees, these insects live individually, with each female constructing her own nest. While recognized primarily as essential pollinators for numerous crops and wild plants, their presence in certain habitats can occasionally conflict with maintenance requirements for turf and gardens.

The biology of the Andrena genus centers on their fossorial behavior. During early spring, females excavate deep burrows in the soil, often creating complex networks of tunnels and brood cells. They provision these cells with pollen and nectar before laying eggs. The developing larvae remain underground, typically completing their life cycle and pupating within these chambers before the following year.

The primary concern regarding Andrena is the physical disruption of soil surfaces. In areas such as golf courses, public parks, or residential lawns, mass nesting can lead to the formation of countless small soil mounds, known as «volcanoes». These mounds create uneven surfaces and disrupt the uniformity of the grass, which can be problematic for aesthetic and maintenance purposes.

It is important to emphasize that Andrena bees are not agricultural pests in the traditional sense; they do not feed on plant tissues, stems, or leaves. On the contrary, they are highly beneficial as they provide valuable pollination services to fruit trees and various horticultural crops. Their negative impact is restricted to human-managed landscapes where soil integrity is a priority.

Management strategies for Andrena focus on site modification rather than eradication, given their ecological importance:

• Maintaining dense grass growth, which makes the soil surface less accessible and less attractive for nesting.
• Increasing soil moisture content during the early spring nesting phase to deter burrow construction.
• Regular rolling of the soil surface to firm up the ground and collapse existing entry holes.
• Applying light mulch or topdressing to cover bare soil patches where bees typically establish their nests.