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Melanagromyza
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Melanagromyza verbenivora
Photo#1984895
Copyright © 2021
John van der Linden
Stem borer, Verbena -
Melanagromyza verbenivora
Van Peenan Park, Decorah, Winneshiek County, Iowa, USA
June 16, 2021
Stem borer that girdled this shoot of white vervain,
Verbena urticifolia
, causing the shoot to wilt.
Images of this individual:
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Contributed by
John van der Linden
on 16 June, 2021 - 11:51pm
Last updated 20 November, 2023 - 7:26am
Moved
Moved from
Unidentified Immature Stages
.
Reared adult(s) identified by Owen Lonsdale.
…
Charley Eiseman
, 20 November, 2023 - 7:26am
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Thank you
*
…
John van der Linden
, 20 November, 2023 - 6:34pm
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Familiar droop
I have a plant which I think is
Verbena
with the tip drooping like that but I haven't spotted any insect sign. Where is the mine relative to the wilted part?
…
John F. Carr
, 18 June, 2021 - 12:54pm
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Immediately below it
In this example the spiral mine around the stem was within 15mm below the spot where the stem transitions from being erect to being droopy. I have been finding similar sign on several different unrelated species of host plants this year, and in every case I've found so far where I've actually dissected the affected plant, the culprit has been a fly larva. The easiest way I've found to locate the spiral mine / confirm that the stem has been girdled is to use a sharp knife to peel or scrape (preferably peel) away a strip of epidermis, starting at the base of the wilted area and going down maybe 30 mm. If the stem has been girdled, the spiral mine should be visible near the very top of the still-erect part of the stem once the epidermis has been peeled away.
…
John van der Linden
, 18 June, 2021 - 5:49pm
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Found it
There is a faint discoloration visible without cutting the stem open.
…
John F. Carr
, 19 June, 2021 - 2:37pm
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Nice find John!
It sure does look like your plant has been girdled. I think it's really neat that you found this, and I'd be very interested to learn what this turns out to be. The flies that I'm becoming familiar with that do this sort of thing at this time of year all pupate inside the stem, with adults mostly emerging straightaway (i.e., during the summer). So, if you wanted to take a stab at rearing this, that would be something to consider.
Melanagromyza verbenivora
is active in upper stems and inflorescences during the summer, and can cause wilting, but so far, it's only known from
Verbena stricta
.
…
John van der Linden
, 19 June, 2021 - 3:23pm
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