What's wrong with my sunchokes?

I planted a patch of "Supernova" sunchokes from Oikos in 2018. They did great for two years and then in 2020 and 2021 they've had some sort of massive disease problem. The leaves gradually turn black and that eventually consumes the whole stem and it dies. Last year it only partially consumed the patch and I still had a good harvest of tubers (no signs of anything wrong on the tubers). This year it seems like the plants were thoroughly overwhelmed before they got a foothold, so I'm expecting there won't be much to harvest.

Here's the puzzler: 2020 and 2021 were very different years climate-wise. 2020 had normal amounts of rainfall and moderate temperatures. 2021 has been a withering heat and drought. So if it were something that thrives in damp conditions, it shouldn't have been able to get anywhere this year. And likewise if it were tied to water stress, it shouldn't have emerged last year when the moisture was fine.

One more oddity: I have another patch of "Gute Gelbe" sunchokes about 20 feet away, and they are showing no signs of trouble. Given how bad the situation is in the one patch, I would think that a lot of pathogens would have been able to make the leap to the other patch by now.

I'll be interested to see what the experts say, but if you don't get any firm resolution, you should plant one of your Gute Gelb tubers among the Supernovae as a diagnostic test for next year. Is it the location or the variety?

Ian, it looks like the leaves are yellowing and dying but the leaf veins are remaining green? If so, it may be a severe magnesium deficiency in that spot.

Have they bloomed yet? They may be dying back to go dormant.

Leigh, I should have clarified that the photo was from July. I've added a couple more photos with dates to show the progression to sad dead sticks. You can see that a few of them tried to put up sad flower buds in August (probably sensing that they were dying), but they were only about 3 feet tall. In a normal year they wouldn't bloom until around now and would be 7 feet by then. The veins do stay green longer than the rest of the leaves, though they still eventually die. It's certainly possible that the soil where they are is poor, but wouldn't you expect that sort of deficiency to have a gradual onset? It seems strange that they would suddenly be in terrible shape in 2020 after not showing any signs of stress in the first two years.

Christopher, I love the idea! I'll give that some thought when I harvest the Gelbes. The tricky part will be marking the test tuber with something that will survive winter intact so I can identify and monitor it next year.

Christopher, I love the idea! I'll give that some thought when I harvest the Gelbes. The tricky part will be marking the test tuber with something that will survive winter intact so I can identify and monitor it next year.

Tada! I use these flaggs for marking my plants. That is, combined with a map.

webpage

Ian, did they produce any sunchoke tubers?

Last year: yes, despite the plants dying back early, they produced a nice crop of healthy-looking tubers that seemed as bountiful as ever.

This year: don't know, I haven't dug them yet. I usually wait until around a frost, but I suppose there's no reason I couldn't dig a few earlier to see. I suspect the crop will be much reduced, if anything.

My first suspicion is sun scorch/scald.  Whatever is killing your plants seems to be doing it pretty uniformly across all of them, pointing to an abiotic cause.  Sunchokes need consistently moist soil.  The fact that the leaves seem to be dying from the outside in makes me think they are not getting enough water.  You said that this year has been dry, but last year wasn't.  I'm wondering if you got enough rain last year for the plants to be consistently moist?
As to the soil being poor (and maybe your prior sunchoke crops in that spot used up what was there that they liked), nutrient deficiencies can show up in a plant when it's not getting enough water.  For example, tomatoes get blossom end rot pointing to a calcium deificiency when they are not getting enough water to be able to pull the calcium they need from the soil.
Can you investigate the plants further? Do you see any mold-like growths or any unusual growths at all under the leaves or around the stems at the soil level? Do you see spots on the leaves where they seem to be rotting from a center point out making the area translucent? Pull up one and look at the roots, dissecting one even, to see if you see anything unusual too.
And where are you located?

Thanks for the ideas, Jen! I've updated my profile with location - I'm in Minnesota, right where the plains give way to forest. We get moderate moisture throughout the growing season, but not enough for the topsoil to be consistently moist all summer, and I don't give the patches supplemental water. If it is sunscald or lack of moisture, that would be an interesting data point to suggest that "Supernova" has very different needs from "Gute Gelbe". Both patches get the same amount of moisture, so that would be a dramatic difference in performance.

I haven't spotted any unusual growths on the plants, but since they're very dead at this point, it might be too late for a close inspection to turn up anything. No translucent areas, pretty sure I would have noticed that when they were more alive. I dug up a couple and don't see anything unusual about the roots. There are some tubers there but they're very small, which isn't surprising since the plants died early and probably gathered very little energy this season.

Ian, if you're in The Cities, I'm about 130 miles north on sandy loam. Our drought earlier this summer was substantial and I had to water my annuals quite a bit. I only watered my sunchoke patch once, when the leaves got droopy, but I did give it a good long soak. My plants are not suffering from whatever yours are. (It's my first year growing them, so I'm no general expert, but I thought I'd provide another datum from "the neighborhood".)

Ian, that is a puzzle.  I'm not sure I would use that location again next year for sunchokes.  You may want to give it a rest if you can.  If you've been using the same site a number of years in a row for sunchokes, maybe a pathogen has built up in the soil.  I did see this from Perdue, "If possible, susceptible crops should be rotated with small grains or corn. Avoid close rotations with dry edible beans, sunflowers, safflower, mustard and soybeans." And this from the USDA, "Rotation for a minimum of three years into a grass family crop (such as maize) is recommended." I would also start in a new site with new tubers as well.
Another thought - if the roots got infected with a pathogen, that could explain why the plants look like they didn't get enough water.... It may all be connected. :/
Good luck!

It looks like you might have a potassium or phosphorous deficiency. It might be helpful to google the words... "mineral or potassium or phosphorous deficiency in vegetable plants" and look at the images. I did that and I am including 2 pictures that both look similar to your sunchokes. This helps me a lot but over the years I have come to realize that say, a potassium deficiency in tomato plants can have similar symptoms but look quite different than a potassium deficiency in cabbages.

I have been adding a lot of new flowering shrubs to my garden these past few years. This summer I have 3 new ones and their leaves kept turning brown all around the edges. Eventually the whole leaf turns brown/black and dies. So, I tried this....  I have filled a bucket with just coffee grounds, rotten banana peels and some dirt that I keep separate from my other compost. When I see it beginning to happen I give the plants a big handful of this compost. Within a week I see lots of new green growth on the plant and the older affected leaves don't get any worse. It seems they are having a potassium deficiency. It works every time. I just haven't figured out how to amend that soil so it will stop happening.

I hope this helps.