Milkweed stem weevil
Rhyssomatus lineaticollis
The reason a healthy milkweed shoot suddenly wilts from a neat row of punctures partway up the stem.
What it does on milkweed
The female chews a short row of punctures through the stem wall, lays into the pith, and the hatching larvae tunnel through the stem before dropping to pupate in the soil. The wound is often the visible symptom: a shoot wilts above a small ladder of scars. Adults also feed on leaves and shoot tips.
How to recognize it
A stout black weevil about 6 to 9 mm with a downcurved snout and fine ridges along the thorax. The evidence is easier to find than the insect: a neat vertical row of punctures on the stem.
Where and when
Eastern and central North America. Most often seen May to July.
Should you do anything about it?
Nothing worth doing. A stand loses a few stems and carries on. Cut out and bin a badly tunnelled stem if you like tidiness.
Milkweed stem weevil: common questions
Why is my milkweed stem wilting halfway up?
Look for a short row of small punctures below the wilt. That is milkweed stem weevil, and the larvae are inside. The plant recovers from the base.
Cite this page
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Milkweed USA. (2026). Milkweed stem weevil (Rhyssomatus lineaticollis). Retrieved DATE, from https://milkweedusa.com/wildlife/milkweed-stem-weevil/
"Milkweed stem weevil (Rhyssomatus lineaticollis)." Milkweed USA, 2026, https://milkweedusa.com/wildlife/milkweed-stem-weevil/. Accessed DATE.
Milkweed USA. "Milkweed stem weevil (Rhyssomatus lineaticollis)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/wildlife/milkweed-stem-weevil/.
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title = {Milkweed stem weevil (Rhyssomatus lineaticollis)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/wildlife/milkweed-stem-weevil/},
note = {Accessed DATE}
}