Small bees breeding in loose soil #626088 - Ask Extension

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Small bees breeding in loose soil #626088

Asked April 21, 2020, 11:49 AM EDT

Hi, I am hoping you can help me with some advice and information. We own one of those little brick houses in the historical center of Frederick. I was attempting to remove the mangy grass and double dig the soil from our small back yard (600 SF) in order to turn it from a bad lawn to mow, into a garden. It was hard work, but manageable, and the underlying soil, once cleared of stones, bricks, broken dishes and toys, bottles, tree roots, etc. seems quite goood - friable, rich looking, etc. I hurt my back doing all this digging and had to stop for a week. I left a largish pite of bare soil exposed. Within a few days the soil was overwhelmed by small, mostly black, bees digging into shallow tunnels apparently to breed. I turned over bit of the soil to find it full of larvae. The rain last week and cold temperatures seemd to discourage them and I thought the problem was solved, but on Sunday a few were back and the soil is still packed with larvae. I don't know about these bees and the landscaper suggested calling an exterminator. Before going to a nuclear option, I wanted to enquire if you were familair with these bees and what we could expect. We are inclined to leave them alone since they are presumably polinators, assuming they will relatively quickly mature and fly away. If they are going to be a regular pest, I will reluctantly have to get more agressive. They don't seem very aggressive, but the back yard is unusable with them there and I cannot move the soil without disturbing the larvae. It may be as simple as getting a sprinkler - they don't seem to like the wet. If it is just a matter of time (not too long), we can wait for them to finish and go away. If you have any informtiaon or advice about these bees you could share I would be most appreciative. We would much rather live in relative harmony with our birds and insects if they are not going to be terrible pests. The bees aren't very good companions on the patio. The mourning doves nesting in the transom over the kitchen door are a little wierd, but fine. This an urban location 1/2 block off Market Street and 4 blocks North of Patrick Street - so not in the countrty. The picture is the now bee-infested dirt pile. Thank you very much. EHH

Frederick County Maryland

Expert Response

While exact identification of these bees is challenging without a photo (and possibly even difficult with one), they sound like one of our many ground-nesting bees. While solitary, they can nest communally if in ideal habitat. Without a hive to defend, they are not prone to stinging and will not bother people. Altering the habitat is the only practical way to discourage and eliminate them. That said, they are beneficial insects and good pollinators, so leaving them undisturbed would be best. The adults will be done breeding and expire in a month or less; the larvae will spend the summer maturing and overwintering in their burrows until next spring. Unfortunately, there is no practical way to relocate the larvae without destroying their cells and food supply. The only way to continue to develop the garden without harming the bees at all is to wait until the adults of this generation emerge next spring and block access to bare soil before they try to burrow and lay eggs. Otherwise, you can level what soil you need to and plant in it (after the adults are gone, if you wish), which will hopefully minimize the bee casualties while allowing some to develop undisturbed between planting holes.
https://extension.umd.edu/hgic/topics/mining-bees-lawns
https://extension.umd.edu/hgic/topics/meet-pollinator-cellophane-bee

Miri

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