Stem Borers- Anyone Have Them Yet?

16 years ago

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

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Here's the wilted stem

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The Frass

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The Frass Inside

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The Culprit

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The Exit Hole

Comments (15)

jroot
16 years ago
an excellent lesson with photos. THanks for sharing.

So far, I have avoided this pest.
oxmyx
16 years ago
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.
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Poochella
16 years ago
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...
linht
16 years ago
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
dahliaboy
Original Author
16 years ago
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
linht
16 years ago
I see...thanks for the useful info!!
penserosa
15 years ago
May I revive this topic? I wonder if Bonide's "Eight" will work on this critter. Has anyone tried it?

Pat
misslucinda
15 years ago
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.
pdshop
15 years ago
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?
dahliaboy
Original Author
15 years ago
Hey Misslucinda,
I'm here......been busy with work, house renovations and
planting my 200 dahlias.
DB
misslucinda
15 years ago
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.
dahliaboy
Original Author
15 years ago
Misslucinda:
Sounds good...Best months for me to talk are Sept
and Oct.
DB
penserosa
15 years ago
So - Bonide's Eight....worth using?
theras_garden
15 years ago
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.
jroot
15 years ago
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.