Beetle Infestation of Oak Trees at Dusk

Asked May 30, 2019, 11:12 AM EDT

Just after sunset each evening, there is a beetle infestation on our oak trees that appears to last for 20 to 30 minutes. There isn’t immediate visible damage to the tree but over the course of a few seasons, it may be the reason that the trees are not flourishing. The beetles seemingly come out of nowhere and there are easily hundreds of beetles on a single tree. Please help us understand if this is indeed hurting the trees and if there might be an eco-friendly solution to battle the infestation.

Washington County Minnesota

3 Responses


Hang some sticky traps of branches in the near the area where the bugs swarm at dusk. Take close up pictures of the traps and send the pictures to us. The picture will allow to look at the insects and identify any that could be farming your oak tree.
The next will help you identify the common problems of oaks.
http://apps.extension.umn.edu/garden/diagnose/plant/deciduous/oak/

I captured some of the beetles in a jar last night. Clearer picture is attached that includes top and under sides, along with approximation of size. Thank you for your assistance!

May/June beetles are usually brown, rusty, or black and rather hairy beneath. They are nocturnal and are attracted to lights at night. They walk and fly clumsily. They belong to a large family of beetles called scarabs. As with other scarabs, they are oval, stout, and have clubbed antennae with segments that can press tightly together or can be fanned open like a feather. The larvae are commonly called white grubs. The larvae feed on the roots of grass. May/June beetle cause little damage to oak trees.

https://hort.extension.wisc.edu/articles/mayjune-beetles/

https://extension.umn.edu/corn-pest-management/white-grubs