Parsnip Clotworms

[Fred Schueler]

Everyone,

We try to manage the wild Parsnips around our houses to maximize the
populations of Parsnip Webworm Moths on them, and this spring the
caterpillars seem to be webbing the unexpanded flower umbels rather than
"waiting" until the umbels are open - the partly-in-focus attached photo
is characteristic. I'm not sure I haven't noticed this in previous
springs, but there are not any webbing over an expanded umbel yet.

fred.
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Frederick W. Schueler & Aleta Karstad
Fragile Inheritance Natural History - https://fragileinheritance.ca/
2024 annual letter: https://clt1233162.bmeurl.co/11E63979
6 St-Lawrence Street Bishops Mills, RR#2 Oxford Station, Ontario K0G 1T0
on the Smiths Falls Limestone Plain 44.87156° N 75.70095° W
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[P Auritus]

But.... do you think they are having a population-level effect on the parsnips? Or are they mostly just reducing the size of the foliage, with the plants still able to breed and spread?

Shane

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[Fred Schueler]

On 7/4/2025 5:44 PM, P Auritus wrote:

> But.... do you think they are having a population-level effect on the parsnips? Or are they mostly just reducing the size of the foliage, with the plants still able to breed and spread?

* we're looking to see what happens - it's hard to see if the reduced
seed production reduces the abundance of the 'nips around here, though
we certainly have a lot more Webworms than roadside stands have.

The thing about Parsnips is that the "poison parsnip" trope is whooped
by the herbicide companies, and the fact that a biocontrol species is
already present is completely ignored in discussions of the Parsnip's
status. The conventional control methods (mowing, citizen pulling, &
herbiciding) are harder on the Webworms than they are on the Parsnips -
https://ngtimes.ca/does-mowing-down-the-golden-parsnips-sustain-them/ -
because the Webworms are univoltine, so they can't recover to go after
reblooming of controlled Parsnips.

Nobody has done research to see what could be done to promote the
over-wintering of the adult moths, and it looks, from some of the
checking on pupae (in the stems of the Parsnips) that we have done, that
there is a parisitoid that takes out a lot of the Webworm pupae. This
fall we ought to bring some the stems with pupae in, and see if we can
get adult parasitoid mini-wasps.

fred (p.s. - the thing that has struck me this summer is the incredible
pale green beauty of the sculpture and fluting of the stems and umbels
of the second year plants)
=========================================

> On Thu, Jul 3, 2025 at 10:19 PM Fred Schueler <bck...@istar.ca
> <mailto:bck...@istar.ca>> wrote:
>
> Everyone,
>
> We try to manage the wild Parsnips around our houses to maximize the
> populations of Parsnip Webworm Moths on them, and this spring the
> caterpillars seem to be webbing the unexpanded flower umbels rather
> than
> "waiting" until the umbels are open - the partly-in-focus attached
> photo
> is characteristic. I'm not sure I haven't noticed this in previous

> springs, but there are not any webbing over an expanded umbel yet. - fred.