when to harvest potatoes with diseased vines

Hi,

I'm growing potatoes from Cultivariable TPS, wide tetraploid mix. This is year 2 of this venture; I planted out the mini tubers I harvested in year 1, so this is my first "real" crop. I'm in central VA in zone 7, and I planted out the mini tubers on March 18th. Now I'm at the 120 day mark and expected the vines to die down--they have a lot of disease but aren't dying back all that much yet. My question is, when should I harvest?

I pulled one plant yesterday to see how the spuds were doing, and some were ready but most still really small. I can't tell if the taters are small because they need more time in the ground, because of disease, or because I accidentally crowded the plants (the vines ended up being way more massive than I expected).

Should I let them ride until first frost? I'm afraid the blight & assorted diseases (and I'm guessing there are several lol) will get into the tubers. Attaching pics of the vines and the potatoes I dug up yesterday.

Thank you!!!

What I will explain relates to storage potatoes. This wont matter if you plan to dig them up and eat them withing a few weeks.

Having grown up on a commercial potato farm (400 acres), your late stage vines look fine. You can either let the vines die and go dry on their own or like us in zone 3 (where frost can ruin the crop if you dont get them out of the ground in time), we had an implement that using propane would burn the vines to kill them. We did this because dry and brittle vines would not clog up our harvesting machinery and it gave the spuds a few days to scab over in the ground. This scabbing over made them more durable to withstand the harvesting process of conveyors and belts and dropping.

So you can either let the vines die on their own (recommended in warmer climates where frost is not an issue)  or you can torch them but regardless of the route you take, let them sit in the ground for 3 days and then be careful when digging so as not to damage the outer skin.

Once out of the ground, (DO NOT WASH THEM) knock off the big chunks of dirt and place them in the shade where they wont get rained on (on a screen or mesh is great but even placing them on wood is ok) This is the storage curing process to dry off the outer skin before long term storage. Cure for 4 or 5 days.

Store them in TOTAL darkness (or they will want to sprout) You can voer with newspaper, brown paper bags or burlap to keep them in the dark. The ideal storage temp is 43 to 45F in high humidity. DO NOT store in a fridg unless you like shrived spuds. Basements and root cellars are ideal for this (cool/dark/damp) If you store them in temps below 43 they will darken, toughen and get an off flavor. (another reason not to store in a fridg as most are set to 40F) Storing in temp too low causes cold-induced sweetening and shortens then shelf life. Also know that spuds need air flow during storage. Dont store them in sealed containers or plastic bags.

Sorry for the long rant but this is all we did (they were our cash crop)

I'm in a similar situation, only no TPS origins.  I've grown potatoes of many varieties in the past, and harvested after the blossoms were done.  This year, after learning more about potato breeding, I was hoping to get some seed berries.  My plants were very vigorous, and have fended off the onslaught from Margined Blister Beetles & to a lesser extent, spotted & striped potato beetles.  The blister beetles ate the leaves until they were fat & plump.  I ended up using needle nose pliers to snatch them off my plants, which worked out very well.  This was my first time with this pest, and now that I know how to deal with them, future crops will be better.

I thought the plants were done, but now that they've had the pests removed, the foliage is flushing out again.  So, in this instance, I'm going to experiment with letting them go until they die back on their own.  I do know of others in my area that just harvested last week.  While I don't know if they'll get bigger if left in the ground longer, my thinking is that like any root crop that undergoes a dormant period, the drawing down of moisture & nutrients from the leaves & stems as they die back goes into the roots (tubers).  This could make them larger, but since photosynthesis has stopped & the plant is going dormant, I'd doubt it amounts to much.  Also since the blooming & possible fruiting has happened by now, the energy would theoretically just be conserved in the tubers for next year's growth (I have overwintered some small missed potatoes in the soil, & they grew fine the next year in zone 6).

Since I also have other things in my potato hill row (a few 2nd year carrots for seed collection & some winter squash plants that will likely grow up until frost kills them), I've decided that this would be a good year to experiment with leaving them in the ground until at least the fall, if not by winter.  Who knows, maybe they'll last longer in storage this way?

As far as your question about blight & disease, I would like to know more about that as well.  I imagine viruses are throughout the plant, even in tubers, but blight is usually fungal & doesn't affect all of a plant to my knowledge.  I did read an account somewhere that someone grew store bought potatoes that sprouted, and kept them going year after year by simply selecting the best ones to replant (still healthy looking/no rot/stored well/etc.)  Another documentary I saw said something like 5 years is about the extent of time you can grow potatoes continuously before the virus load gets to be too much.  All I know is, I'm still learning every year, but I like the idea of TPS.

Thank you Ron! Sounds like they're okay, I'm gonna let the vines die on their own.

Cy, good point about it taking a while for the virus load to accumulate. I'm planning to grow the potatoes as a "biennial"...save tubers this year, then save TPS the following year, so I can start fresh with viruses from time to time.