Joe Pye Weed Dying
I have a stand of Joe Pye Weed and noticed some of the stems are dying off. I look closely and there are small holes in the stems. I saw a small whitish caterpillar with black stripes inside one of the holes. I also noticed small piles of something? beneath the stems. Any idea what's happening or what I can do? I'm not sure if the cause is insect damage or not. Next to the Joe Pye is a stand of rudbeckia that is wilting and dying off but I can't find any insect damage on the rudbeckia plants. So many two separate issues at play here?
Howard County Maryland
There are a couple of eupatorium borer moths: one is a clearwing moth and looks like a wasp, the other is a gray-brown one. They are not commonly a problem.
For control, clip off any bored stems where the caterpillars inside and destroy. There is no insecticide that will treat them inside the stems.