Bad case of early blight on potatoes ... damage control?

OneDahlia · June 25, 2012

I'm a pretty new gardener and this is my first year growing potatoes. The leaves started yellowing a few weeks ago, and in a quick google search I read that you're supposed to leave the potatoes in the ground for a few weeks after the plants yellow and die, so I figured it was just the natural process. (Admittedly, I am not being a very attentive gardener this year.) Well, now that I let it go awhile, I'm seeing that they're not just yellow, they now have brown spots and brown leaves too. It looks like early blight, and a bad case of it. I was afraid for awhile that it might be late blight, so I dug under one plant and came up with a few perfect (and yummy!) potatoes, so at least it's not something that's affecting the potatoes.

My question is now that I've let it progress this far, what's the best damage control? I'm not sure I will be able to control this on the potatoes, but at least I don't want it to spread to the tomatoes. Some of the potato plants are pretty much completely affected. Others have a lot of leaves that are still green. Should I pull out the worst plants, prune the others heavily, and spray with Daconil? Or should I get rid of all the plants at this point? And if I do that, do I harvest all the potatoes, or can they stay in the ground for awhile?

**Tom Wagner** · June 26, 2012

Early Blight hits potatoes late and any late spraying is not going to do much good.
Tie that in with extremes of wet and dry periods...no small wonder for the blight to spread.

The season in Virginia potato harvest is mid June through early July....therefore I would just enjoy what potato tubers you can get. The blight will hit vines less vigorous or those with fertilizer problems...so that would be a good place to lift those hills. Sometimes, but rarely, the blight will cause spots on the tubers which will shorten the storage time...but if you can't eat them all just hill up the rows to protect the tubers from the sun and dig as needed. If you do lift them early be sure to store them in the coolest place you can find out of any light source.

Since I am a potato breeder...I have found late maturing varieties to hold up better against early blight....but retail outlets don't carry late varieties. However I do well with late varieties since even today at 3:30 in the afternoon it is only 56 F for a high. Our night time temps are around 47 F. People around here walk around with parkas all day long.

Tom Wagner

OneDahlia · June 26, 2012

Thanks, Tom! I pulled the worst plants and pruned the others this afternoon, but it sounds like I should just go ahead and cut down or pull all of the plants?

I'll leave the potatoes in the ground till the kids get back from a vacation so they can enjoy the hunt.

I'll spray early and often next year!

wingnut · June 27, 2012

Just remember you can't UNSPRAY your land, so maybe grow your potato crop from seed produced from resistant varieties instead. You will also find that these are also better tasting than commercial high input (fungicides and pesticides) varieties.

June 25, 2012	#1
OneDahlia Tomatovillian™ Join Date: Sep 2011 Location: 7a NO. VA. Posts: 202	Bad case of early blight on potatoes ... damage control? I'm a pretty new gardener and this is my first year growing potatoes. The leaves started yellowing a few weeks ago, and in a quick google search I read that you're supposed to leave the potatoes in the ground for a few weeks after the plants yellow and die, so I figured it was just the natural process. (Admittedly, I am not being a very attentive gardener this year.) Well, now that I let it go awhile, I'm seeing that they're not just yellow, they now have brown spots and brown leaves too. It looks like early blight, and a bad case of it. I was afraid for awhile that it might be late blight, so I dug under one plant and came up with a few perfect (and yummy!) potatoes, so at least it's not something that's affecting the potatoes. My question is now that I've let it progress this far, what's the best damage control? I'm not sure I will be able to control this on the potatoes, but at least I don't want it to spread to the tomatoes. Some of the potato plants are pretty much completely affected. Others have a lot of leaves that are still green. Should I pull out the worst plants, prune the others heavily, and spray with Daconil? Or should I get rid of all the plants at this point? And if I do that, do I harvest all the potatoes, or can they stay in the ground for awhile?

June 26, 2012	#2
Tom Wagner Crosstalk™ Forum Moderator Join Date: Aug 2006 Location: 8407 18th Ave West 7-203 Everett, Washington 98204 Posts: 1,157	Early Blight hits potatoes late and any late spraying is not going to do much good. Tie that in with extremes of wet and dry periods...no small wonder for the blight to spread. The season in Virginia potato harvest is mid June through early July....therefore I would just enjoy what potato tubers you can get. The blight will hit vines less vigorous or those with fertilizer problems...so that would be a good place to lift those hills. Sometimes, but rarely, the blight will cause spots on the tubers which will shorten the storage time...but if you can't eat them all just hill up the rows to protect the tubers from the sun and dig as needed. If you do lift them early be sure to store them in the coolest place you can find out of any light source. Since I am a potato breeder...I have found late maturing varieties to hold up better against early blight....but retail outlets don't carry late varieties. However I do well with late varieties since even today at 3:30 in the afternoon it is only 56 F for a high. Our night time temps are around 47 F. People around here walk around with parkas all day long. Tom Wagner

June 27, 2012	#4
wingnut Tomatovillian™ Join Date: May 2011 Location: bald hill area thurston county washington Posts: 312	Just remember you can't UNSPRAY your land, so maybe grow your potato crop from seed produced from resistant varieties instead. You will also find that these are also better tasting than commercial high input (fungicides and pesticides) varieties.