Stem Borers- Anyone Have Them Yet?

dahliaboyJuly 22, 2007

Hi All:

I was away on business for a little over two weeks and

came back to some stem borer damage to a few of my dahlia

plants. These particular borers were from a moth. I've

attached some photos of the damage and the culprit.

Usually the moth will lay her eggs on the stem of the leaf close to the stalk. The larvae will bore into the plant and eat away until they are mature enough to exit. They destroy the vasular system of the plant and cause a wilt in the affected branches/stalks. You'll also notice their frass in the crotch where the leaf meets the stalk. You can usually cut off the affected stalk and move on.

DB

Here's the wilted stem

a href="http://photobucket.com" target="_blank">
The Frass

a href="http://photobucket.com" target="_blank">
The Frass Inside

The Culprit

The Exit Hole

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jroot(5A Ont. Canada (near Guelph))

an excellent lesson with photos. THanks for sharing.

So far, I have avoided this pest.

    Bookmark   July 22, 2007 at 9:39PM
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oxmyx(6)

Had that once
I beleive it is the same borer as the squash vine borer.
hard to get rid of. eggs should be at the base of the plant - rusty red disks. I squish them.

I am sure you know what to do DB, just putting in my 2 Cents.

    Bookmark   July 24, 2007 at 12:47AM
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Poochella(7 WA)

Great photos. I was cowering in the dahlia beds today hoping I wouldn't find any wilted stems.

DB you might offer to share your photos with www.dahlias.net or the ADS website or other. I think it would be a great addition to their pest information sections and a service to all dahlia growers with those excellent photos. Just a thought...

    Bookmark   July 25, 2007 at 1:40AM
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linht(4a)

DB, if the disgusting worm is nowhere to be found, how do you differentiate between a stem boring problem and stem rot?? I've had several wilting problems but I don't know what it's from. I don't know how to post pics on here so I just included the link at the bottom. Anyone with any answers or ideas, please advise!!! Thanks!

Tracy

Here is a link that might be useful: stem rot

    Bookmark   July 26, 2007 at 10:21PM
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dahliaboy

Tracy:
The way you will know if it's a stem borer is if you see an exit hole like I show and the presence of Frass which is the excrement of the larvae. Look at photo #2 and you'll see where to look for the frass.
DB

    Bookmark   July 27, 2007 at 7:30AM
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linht(4a)

I see...thanks for the useful info!!

    Bookmark   July 27, 2007 at 5:45PM
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penserosa(z6 NJ)

May I revive this topic? I wonder if Bonide's "Eight" will work on this critter. Has anyone tried it?

Pat

    Bookmark   June 17, 2008 at 4:28PM
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misslucinda

Yes you may revive and in answer to #2 I just don't know.

However, I was wondering what has happened to DB. I brought a pal to one of his talks and now she is an avid dahlia gardener. I have people who want to talk with him about a lecture.

    Bookmark   June 17, 2008 at 10:37PM
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pdshop(5)

I am so glad you found the culprit. I hate to think of what happened to him. Bird food? Anyway, can you use something to avoid the borers or is it luck?

    Bookmark   June 19, 2008 at 9:23AM
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dahliaboy

Hey Misslucinda,
I'm here......been busy with work, house renovations and
planting my 200 dahlias.
DB

    Bookmark   June 20, 2008 at 10:39AM
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misslucinda

Hey DB-

Glad to see you are still checking into the forum. If you are doing house renovations, you must be doing well!! I'll forward your telephone to the member of the local GC Program Committee who inquired.

    Bookmark   June 20, 2008 at 10:47AM
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dahliaboy

Misslucinda:
Sounds good...Best months for me to talk are Sept
and Oct.
DB

    Bookmark   June 21, 2008 at 12:36AM
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penserosa(z6 NJ)

So - Bonide's Eight....worth using?

    Bookmark   June 21, 2008 at 9:44AM
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theras_garden

Thank you for the wonderful photos, DB. That's the lil bugger that destroyed my squash crop this year. Borers not bad last year (cause of GA drought?) but this year they're huge problem (still in drought but had more spring rains).
I'm horrified you are showing them in dahlias. My dahlia bed is hop, skip, jump, and short moth flight from veggies to dahlias.

    Bookmark   June 24, 2008 at 1:07PM
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jroot(5A Ont. Canada (near Guelph))

I have a couple that are wilting, but their neighbours are not. Your posting made me curious, so I went out to see if there was evidence of holes or frias. I can't see any. The ground seems to be not dry, and yet, if I put water on it, the plant picks up. Strange. I'll keep my eyes open, and maybe replace the culprits.

    Bookmark   June 25, 2008 at 7:21AM
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