One could hardly miss the frass surrounding the willow oak tree next to the vending area in Catch the Wind, it was everywhere. Of course, if you don’t know what frass is then you may not have noticed it, thinking it mulch that had been blown onto the sidewalk by the wind.
Well, it wasn’t mulch, it was caterpillar poop, or frass, a sure sign that there are caterpillars above. With this much frass there must be many caterpillars feeding above. There were. Hundreds of Orange-striped, or Orange-tipped, Oakworm (Anisota senatoria) caterpillars were munching away on the young willow oak tree.
Orange-striped Oakworm caterpillars are the larvae of the Orange-striped Oakworm moth. The moths lay hundreds of eggs on the undersides of an oak tree’s leaves, and the larvae that hatch from those eggs can defoliate a small tree rapidly and thoroughly. According to what I’ve read about them, the defoliation doesn’t seem to kill or do lasting harm to the tree since it often happens late in the season. However, this seems a bit early in the season for this group of orange-stripeds to be munching away.
The tree in question has not been totaly defoliated though, and I’m sure it will survive. A look at the tree this morning (7/26) revealed no caterpillars, they had all eaten their fill, crawled out of the tree and those that hadn’t been stepped on or run over have dug into the ground where they will remain until next year.
Here are some photos of the caterpillars.
I most often see these caterpillars on willow oak, but other oaks are also used. And, its always a young oak tree that I see them on, but that may simply be a result of my not noticing them higher up on the mature oaks.
I’ve never actively sought out these caterpillars so if they’re not on the ground or somewhere close to eye level I probably wouldn’t see them at all. But as mentioned, frass on the grass (or sidewalk) is a dead giveaway, and a clear sign to look up.