Irises forum→Caterpillar damage similar to iris borer, but a different species

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Name: Ruth
Pittsburgh, PA (Zone 6b)
Irises Seed Starter Region: Pennsylvania Bulbs
Sep 6, 2020 2:58 PM CST
I found a caterpillar in an iris I purchased from a supplier in Oregon, and I wondered if any of you west coast people could help me identify it. When the rhizome shipment arrived I put them in temporary pots, since I knew I wouldn't be able to plant them for a few weeks, and noticed that one had a hole near the center of the fan. I should have taken a closer look, but was potting them in a hurry, and then forgot about it. Today I noticed that this was the only iris that showed no sign of growth and took a closer look. The damage was to the interior central area toward the base of the fan and looked very similar to iris borer damage (including a mess of frass that was starting to rot), but the little monster I pulled out looked completely different. I've had no luck identifying it. Has anyone seen this beast before? It's about an inch long, pale yellow-green with three lateral lines and three distinct bands, one at the front of the last segment and two about a third of the way down from the head. (Pictures are attached.) I'd like to contact the seller and be as specific as possible.
Thumb of 2020-09-06/Riversong/3abd63

Thumb of 2020-09-06/Riversong/87f898

Name: Laurie
southeast Nebraska (Zone 5b)
Irises Butterflies Bulbs Cat Lover
Sep 6, 2020 10:32 PM CST
Hi Ruth,
I did a little looking around online. A few pictures of tobacco budworm (Chloridea virescens or Heliothis virescens) resemble your picture. The articles below discuss the pest, which feeds on many plants, usually on the buds or flowers, but the second article below mentions they will feed on leaves. Apparently the caterpillars are quite variable in color. It does occur in Oregon.



This is just a possibility. Good luck!
[Last edited by lauriemorningglory - Sep 6, 2020 11:15 PM (+)]
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Name: Ruth
Pittsburgh, PA (Zone 6b)
Irises Seed Starter Region: Pennsylvania Bulbs
Sep 7, 2020 12:25 PM CST
Thank you! Yes, I think that's it. This type of caterpillar isn't capable of surviving a typical winter here but petunias bought at a nursery sometimes have them. I've never seen one so darkly pigmented or so big, though I'm usually too busy pulling them off petunia plants and squishing them to pull out a ruler and measure one.

I was looking up pictures of cutworms, leaftiers, armyworms and the like, and it never occurred to me to think of a budworm. How odd that one would bore its way into an iris fan. It's a little worrisome, too. I usually put petunias on my porch and there are irises planted nearby. I guess I'll have to keep an eye on them for this type of damage. Like iris borers these caterpillars seem to carry rot with them.

It's possible that this little beast made its way from one of my petunias to this iris, though I don't think it would have time to get so huge, and there was already damage when the rhizome arrived in the mail. I'm not looking for a refund (Montmartre is easy to find and not very expensive), but I should probably let the supplier know about it.

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