Volunteer potatoes in last year's blighted patch... take a chance or yank 'em?

[tankgirl73]

Last year I built a HUGE raised bed box for potatoes, 6'x4' and 10" deep and filled with 100% compost/manure. Planted three kinds of potatoes, they grew like gangbusters, got huge... and then got blight.

I picked icky bits off as best as I could and still ended up with a decent crop, but it was starting to spread to the tomatoes around the corner... it really ended up being quite ugly and gross.

I pulled all the plants and got rid of them, and dug through the whole box multiple times to get any stragglers, get rid of all organic material from the infected plants.

This spring, I decided to use the box for carrots. 100% carrots! Hundreds of beautiful carrots, carrots don't get blight, lots of room to grow, a great use for the space. I dug through the box again, adding some new compost, looking for potatoes I missed.

Now that it's nearly June, though... there are some volunteer potatoes sprouting. Apparently I missed quite a few, there are at least a dozen little plants! (I think a few close together are from a single potato, but still...)

Part of me says "YANK THEM NOW, don't take the chance, there could be blight in the soil..."

Part of me says "they're volunteers, they've tried so hard, they're so brave and strong, they look so healthy... you could always just yank them later at the very first signs of illness, maybe the fungus didn't survive the winter... why waste a healthy plant?"

Especially since I haven't got any potatoes planted anywhere else yet this year either...

So what do you think? Has anyone actually grown potatoes in a blighted patch the next year with no problems? Or am I tempting fate too much?

[tankgirl73]

No response?

I've done some more research and I'm still unsure. The usual advice is to always destroy volunteer potatoes, because it's infected tubers that carry the disease to the next year.

But if the tubers aren't infected, it should be fine. When I harvested last summer, only a couple potatoes showed any sign of infection... the plants themselves were a mess, but it didn't seem to get into the potatoes.

Also, apparently the ONLY vector (in North America, where so far there's no sign of the 2 mating types producing oospores) is infected tubers, that it is not carried in the soil or rotted foliage etc. I carefully destroyed/threw out all the plant matter last year and was actually panicking a bit that I'd left some in a pile too close to the patch for too long... apparently I don't need to worry about THAT.

But I do need to worry about the tubers. Maybe. Apparently, blight does not survive when tubers are frozen. But from the various sources I've read, it's not clear whether it means that tubers that got frozen will DIE and not produce volunteer plants, or whether tubers that got frozen can grow safely. One site even said blight survives on infected tubers "unless the tubers freeze during the winter or are deep enough in the soil to sprout", which just confused me all the more.

If I dig up the plants and look at the sprouting potatoes, and they look disease-free, maybe I'll chance it. But I dunno. Sigh... I'd really appreciate input from anyone who's been through this before!

[emnic77]

Ughh....I dunno. This is our first year doing potatoes, I've got about the same set up as you (4'x8' bed, 16-18" deep - three types of potatoes...what was your yield??)

Blight is so nearly impossible to get out of your soil, I have to imagine they would be infected too. But, can you rotate a crop that's blight resistant (like your carrots) that won't catch it, but keep a close eye on them so as to not cross contaminate anything else? Just mulch the crap out of your tomatoes either way...

I'd be tempted to leave them for the reasons you mentioned

[1blueheron]

are you growing potatoes/tomatoes elsewhere this year? If so, I'd pull 'em, not worth the scanty yield my volunteers usually have.

[tankgirl73]

Tomatoes elsewhere, yes. Potatoes elsewhere, only limited.

My yield last year was small but tasty... considering the summer weather was just HORRIBLE, my yield in EVERYTHING was small, not just the blighted potatoes. Peppers never grew taller than 6-8", I got about 3 finger-sized cucumbers from 4 plants (squirrels got most of those too...) Green beans did well, but still the plants never got very tall. Onions were tiny, but I was impressed they grew at all because the sets were about 10 years old!

Really, my potatoes and tomatoes did the best... tall, bountiful, bushy, strong! But then, uh, diseased argh...

This afternoon I went out and dug up the volunteers to have a look at their "source" potatoes. I'm disappointed I missed them lol, they look like they would have been tasty!

Most of them, I tossed. There were what MIGHT be the brown scabby markings of blight on them. Hard to tell. No sign of rot or brownness on the inside, but better safe than sorry. One even had some kind of lesion on the underground stem... don't know if that's related or not, but I tossed it.

But there were 6 that looked brand-spanking healthy. So I decided I'll experiment with those ones and see for myself! I did re-distribute them rather than just leave them where they were. I think one of my problems last year (I know blight was a problem everywhere last year, but this made it worse) was that the plants were overcrowded. So I spread these guys out and gave them LOTS of space. The rest of the bed is filled with carrots.

I'm also going to keep a super-close eye on them. Last year was the first time I've ever seen blight. I actually noticed it on the plants for several weeks before I did anything about it -- I thought it was just some sort of bug damage, or dried leaves, or something, I didn't know it was BLIGHT, ya know? Then I really didn't know how to deal with it.

This year I'm better informed and prepared. The moment I see a single telltale spot on any one of those plants, I'm going to assume they're all too risky and pull them all.

My tomatoes are around the corner of the house in separate beds. It was quite late in the season last year before the blight made it to them. By that time, they were pretty well destroyed by septoria... and there was only a tiny bit of blight that I saw. (Ended up pulling most of the plants and ripening all the tomatoes inside... had fresh ripe tomatoes (albeit small) for 2 more months, and a yield of about 50 lbs from about 15 plants).

And yes, I'm going to mulch them! I know now that soil splash-back is a huge contributor to septoria, and I don't ever want to have to deal with THAT again ugh...

I'm doing lots of experiments this year -- seeing what happens if I try ginger root, and spring-sown garlic, and whether we can grow melons here, and potatoes in a coffee sack lol...

[emnic77]

This is a big experimental year for us as well.
We put in a sparse garden last year as we moved into our house mid-june...blight hit my tomatoes hard, which sucked because I had a *bumper crop* of paste tomatoes...boo.

[tankgirl73]

Ha! My tomatoes were all paste tomatoes. And we moved into our house late june/early july *2* years ago, last summer was the first time I tried a garden here. Did some experimenting then too... one result of which is that I won't be trying broccoli or rutabagas again anytime soon!