Larvae identification on red oak

Asked August 4, 2019, 10:10 AM EDT

Hi, I have a very large red oak tree in front of my house. For the second year in a row it has been infested in early August with these larvae that eat the leaves, cover the driveway in frass, and then drop all over the garden. There are no webs or bags. Can you identify them please and let me know whether I need to treat them? I would prefer not to use pesticides but the tree is important to us. I could probably prune some of this out with a ladder. I am including pictures below. Thank you so much!

Howard County Maryland

3 Responses

These are orange striped oakworms, a very gregarious species. They are native and usually not a big problem because other native insects parasitize them.

Big trees like yours can tolerate the feeding of these late summer caterpillars. It doesn't kill the branch, and the tree has had enough time to store carbohydrates in its roots all summer and won't miss a few leaves. (Trees grow more leaves than they need, anyway.)

The only problem is when they get on a small or very young tree and defoliate it more than one year in a row. In that case, you can remove them or spray with spinosad when the caterpillars are small.

If a gang of these are in a location where you can easily reach them, then manually pull them off and drop them into a bucket of soapy water to drown if you like.

Be mindful that caterpillars are a huge food source for birds and should be left to provide for them when at all possible.


Thank you so much for this quick and very helpful response! I will stop worrying and leave them on and hope to feed some birds. :-)