The Parsnip Webworm: Nasty on Nasty
Didn’t see many webworms on your website, but I think I’ve correctly identified this one as a parsnip webworm? I thought this volunteer plant in my yard might be yarrow (which I wanted), so I became obsessed with finding out what was destroying it with these yucky webs. Turns out my plant is Wild Parsnip, which can cause really bad reactions to people’s skin because of something called “furanocoumarins” that it secretes in order to try and ward off these darned parsnip webworms. Seems it causes sunburn-like rashes and even blisters, along with a sensitivity to sun exposure. I couldn’t find any information about whether the worms have anything good about them, so I finally dunked the whole mess (plant and all) in soapy water. I’m not a bug killer by nature but had to get rid of the plant, so I hope I did the right thing. This just seemed like nasty on nasty, am I right? Here are some pictures of what the nasty little webworms did to my nasty little parsnip, before I destroyed the whole thing.
p.s. Almost everything I found online talking about parsnip webworms or wild parsnip seemed to come from Illinois, which is where I happen to be. Made me wonder if they’re especially bad here, or something?
We really don’t care to pass any judgement regarding if you did the right thing or not, but we are very happy to have your letter and image to post. This is a new species for our site and we are very happy you saved us what might have been hours of research to properly identify the Parsnip Webworm, Depressaria pastinacella. BugGuide has a few images that match yours and they provide a link to a site with more information.