Our early spring brought the bees out

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included. 

This is the time of year when I get calls about swarms of little bees going in and out of small holes in the ground. There are several species of solitary bees (Andrenidae primarily) that nest in the ground and become active first thing in the spring. These bees construct individual nest tubes in the ground in which they raise their brood. Each female bee mates, provisions the nest with pollen and lays eggs; they do not cooperate or help each other. Even though they work alone, they do appear to enjoy the company of others and commonly nest in large congregations.

Females prefer to excavate their nesting tubes in sandy soil that receives morning sun where the grass is sparse. Nest holes are dug during the evening hours and may reach a depth of six or more inches. During the day, the active females collect pollen and nectar to carry back to the nest. A single egg is laid upon the pollen ball. After hatching, the larva feeds on the pollen and develops within the tube until it reaches adulthood in the fall. The new adult remains in the borrow throughout the winter until the following spring when bee activity begins to pick up as the nesting cycle resumes. Though adult bees feed on nectar, none store honey, as such. Ground nesting bees play an important role in pollinating crops and wild plants. They are extremely docile and very reluctant to sting, and therefore, essentially harmless. They should be allowed to carry on with no attempt to kill them off. Most are only active for a few weeks so, at most, they pose only a temporary concern. Outdoor activities, including lawn mowing, can be normally conducted with little or no worry of being stung.

Homeowners who are deathly allergic to bee stings and who do not wish to tempt fate may wish to rid their yards of these bees. The best cultural control method is to establish dense turf in the area(s) that the bees favor. Heavy watering or irrigation with a lawn sprinkler during the nest-building period may also help to discourage nesting behavior. If the soil or location is not conducive to a healthy, dense lawn, then 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. 

The most aggressive control strategy is using insecticides to kill the bees. If the nest area is small, then Sevin Garden Dust can be applied to the holes. Larger areas may be easier to treat with a small, hand-held sprayer using any number of insecticides registered for use on lawns.   Be sure to read and follow all instructions and safety precautions found on the label before using any pesticide.

Andrenid bee
Photo 1. Here’s an andrenid bee, one of
several species of ground nesting solitary
bees that are active first thing in the spring.
Photo credit: Joseph Berger. Courtesy of forestimages.org.

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