Damage to dahlia tubers - Ask Extension
I have some pest tracks on my dug tubers. AI suggested millipede damage, not wireworms because the damage is all external on the surface, versus borin...
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Damage to dahlia tubers #924096
Asked January 31, 2026, 10:39 AM EST
I have some pest tracks on my dug tubers. AI suggested millipede damage, not wireworms because the damage is all external on the surface, versus boring holes into the tuber like wireworms are known to do.
Can you please confirm that diagnosis and recommend which beneficial insects/nematodes that can help control millipede damage.
Washington County Oregon
Expert Response
Thank you for your question, Kimber. Dahlia tubers are not known to have insect pest damage, unlike the rest of the (above-ground) plant. Rather, I think that these are lenticels, described as "Puffy, white, or brown warty spots that appear when tubers are in wet soil or during storage, often looking like small cracks. These are not diseased and simply help the tuber breathe." You see them more frequently on tree bark, but they do occur in wet soil. Good luck!
Extension,
No I’m sorry these are not lenticles. You didn’t provide any references but that’s an incorrect diagnosis.
I’m disappointed that you came up with that answer as a Master Gardener. Lenticles are common in the PNW but they don’t look at all like the photo I submitted to you.
That photo clearly showed some chewing track marks on the tuber skin. It likely doesn't harm the tuber itself, it is firm and viable. But as a scientist I was looking for an accurate answer from the Master Gardener program. I had hoped you did a little research and came up with a more serious answer.
Here are 2 images of lenticles on dahlia tubers. And yes anyone who grows dahlias knows what they are, and how they function in wet environments.
Kimber
On Feb 2, 2026, at 12:42 PM, Ask Extension wrote:
I am sorry that you are unhappy with my response. I spent 2 hours researching a response but, after 13 years as a Master Gardener, I confess that I am not perfect, and that this is the first time I have seen the issue. I suggest that you take them into an Extension office where staff can examine them and provide an answer you deem reliable.
