Bumble bees living under porch behind steps

Asked May 8, 2016, 7:57 PM EDT

My sister has a 1950's ranch home that has a cement slab porch supported by a brick under-structure with two built-in stairs. The mortar has deteriorated and a few bricks have fallen into the hole underneath this porch. This Spring, I have witnessed a few huge bumblebees going into these holes where the bricks are missing. I suspect that a nest exists. A member of the house is allergic to bees, but I have read that you shouldn't kill bumblebees due to declining numbers. Suggestions for getting them to move? I have removed all flowers from around the house.

Secondly, there are also different bees that are drilling perfectly circular holes in the mortar between the bricks of the house. What is the best type of insecticide to kill these?

Oakland County Michigan

1 Response

First you need to positively Identify which bee or wasp you have. Several types can nest in homes. Someone who isn't allergic to stings, and is well covered/protected, may need to trap some sample bees/wasps and then ID them. Or send the captured insect to MSU Diagnostic Lab for ID.
Here is a site for identification-

Here is the Diagnostic Lab site- http://www.pestid.msu.edu

The insects nesting in the home behind the step may need professional treatment. If they are honey bees and the comb is large, it may need to be removed. Here is an article with details and options---

The bees in the mortar are probably mason bees. These are beneficial pollinators. They don't create holes but do take advantage of cracks, crevices, and existing holes to widen and then nest in. They are solitary and not aggressive. Males have no stinger, and females don't sting unless threatened. Here is an article that discusses what to do-

You can encourage the mason bees to nest in a more suitable site- here are the details on how to provide nest boxes that they should prefer over your masonry-

And mason bee houses can be purchased from gardening centers, too.
If it is necessary to kill them, pyrethroids such as cyfluthrin labeled for bees and wasps can be used. Always follow all label cautions and directions, and protect your skin, eyes, and wear a protective mask to minimize breathing in chemicals..

I hope this has been helpful.