Is this the dreaded CROWN GALL?

9 years ago

I'm pretty sure this is crown gall but want to verify before doing anything drastic.

I finally dug them today and was so excited to see how many tubers I now have from only 2 plants that I bought in the spring. I didn't notice the bumps until all were dug and washed (i.e. no sterilizing of tools etc)

The suspected clump is two varieties (Sangria and Pineland's Princess) that melded together. The plant gave me a ton of blooms so if it is diseased, it didn't affect the plant at all.

Below is the suspect and underneath is a different one that looks fine except it does have bumps on the tuber itself.

Are either of these Crown Gall?

Featured Answer

cicivacation

9 years ago

Neither of the images are Crown Gall. That looks more like a nasty huge hard foam growth on a tuber.

The top image looks to me like it is Leafy Gall Disease,
caused by the bacterium Rhodococcus fascians. The pimply looking area will produce a whole bunch of sprouts with really thin stems.

I would separate the two clumps, and throw away the infected clump. It will lead to inferior plants next year. The other clump looks like it is fine.

To quote myself, "According to research from
Oregon State Univ, the bacteria can't survive long in soil without plant
matter, but CAN be transmitted via tools to other plants. So sterilize
your digging tool after finding one of these clumps to avoid spreading
it. The soil will be fine for next year's plants."

The bottom image with the 'bumps' are actually 'lenticels,' which allow the transfer of moisture back and forth through the skin. They often become swollen with too much moisture. No worries about those... they only make it difficult to write the cultivar name on the tuber, nothing else.

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Comments (6)

flashphoto
9 years ago
Good Morning cicivacation

I would just like to compliment you on all your posts everywhere on this garden forum. You are a wealth of information and I enjoy reading all your answers. I feel I am taking botany and hort classes. Your knowledge is amazing. What is your background? Thanks for all your posts, and please keep up the good work

Vince
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pinkmauisunset (Zone 5-Central MA)
Original Author
9 years ago
last modified: 9 years ago
Thank you cicivacation!!! You have no idea how relieved I am. I had visions of tossing all my tubers and trying to find a new place to planot next year since I now had contaminated soil. I can deal with Leafy Gall :)

And the bumps from moisture make sense with all the rain we got this weekend.
cicivacation
9 years ago
last modified: 9 years ago
Ah, shucks, Vince... (blushing)

I'm just a hopeless dahlia fanatic who is a self-made researcher who enjoys reading scientific studies and haunts individuals of knowledge until I suck them dry or they run screaming from me. I'm by no means a master grower, but I know how to listen and have been around the block a few times.

Just passing it forward.
cicivacation
9 years ago
Pink, I've had to toss a few clumps over the years showing the same symptoms, but have never had a re-occurrence at the same location. One of them only had the multi-lumps on half, and I saved the other half with no problems the next year.
cicivacation
9 years ago
For the folks that like to dig deeper into matters, here's another viewpoint on the issue, quoted a while back from a dahlia grower that was on the ADS scientific board:

"Fasciation has many causes....bacterial, hormonal, viral, and
environmental like cold, Fungi, mites, insect damage, chemicals, and
genetic mutation. ...Interestingly fasciation is not contagious but if a
bacteria was the causal agent then that can possibly infect other
plant's thru contact....and there is no enzyme involved here.....And it
is never to be confused with Crown Gall."

So according to this grower with a scientific background, Leafy Gall (bacteria) is only one of the reasons for the mess of multiple shoots. But to play it safe, I believe that treating this symptom by assuming contagious bacteria as the source is the safest course of action. And that would be to sterilize the tools and toss the clump.