Indoor small beetle infestation

Asked May 1, 2019, 5:39 PM EDT

For the last few years we have had small green flying beetles show up in our south & east facing kitchen corner window in the late spring in the sunshine. I've been ignoring them until they stopped showing, but this year it has turned into an infestation, with 15-20 new beetles each day. I am guessing that they breeding in the upper corner of the window, but as much as I wipe the window off after I move them outside, they keep coming. They have also made it into both bathrooms on the same floor as the kitchen, but under a handful. It appears to be a type of diabrotica, and these all seem to be from Mexico and south. I am trying to figure out what they are and how to make the house less hospitable so that they will go away and stay away. I have included a photo of one. Thanks for your help.

Multnomah County Oregon

3 Responses

This is one of those good news, bad news stories.The good news is that the insects don't damage anything indoors. The bad news is that they are among the multiple nuisance household invaders that survive the winters in the cozy spaces of our human structures, among them box elder bugs, stink bugs, and lady beetles.

The insect in your image is an elm leaf beetle (Xanthogaleruca luteola) of the overwintering generation. They won't feed or breed indoors. In other words, they're considered to be only nuisance value when indoors.

Do you have elm trees near your house, or on your property? If so, you may see leaf damage this spring.

Our official pest management guide says the following:
". . . the adults fly to trees as the leaves are expanding and chew circular holes in them. Clusters of pointed yellow eggs are laid on the leaves, and the larvae hatch in late spring (typically May-June) and begin skeletonizing leaves. They feed for a period, then migrate to the lower parts of the tree and pupate on the ground or in crevices near the base of the tree. The second generation emerges 1 or 2 weeks later. There are two generations per year."

Fortunately, elms are deciduous trees. As such, they can tolerate a fair amount of leaf loss without serious damage. The exception would be if the tree is young and loses all, or most, of its leaf tissue during the growing season.

To deal with the insects you currently have indoors, continue to get rid of them as you see them, vacuuming or flicking into soapy water. Then, too, caulk and seal any cracks and crevices which allow entry. And ensure that window screens are intact. (Fortunately, the beetles see now will leave of their own accord in mid-spring.)

Later, say about July, caulk and seal outdoor cracks and crevices.

You can find some family photos here:

Thanks, Jean. I have no elm trees. I should check with a next door neighbor to see if she has any. I'll just keep doing what I'm doing. We have our share of stink bugs also.

Often, overwintering insects fly in from miles away. Even if your neighbors have elm trees, getting rid of the trees is very unlikely to stop the problem.