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New blight-resistant tomatoes

Tomatoes and parsley

It looks like this will be another low-tomato year, with septoria leaf spot rushing through our planting despite weekly pruning sessions.  I've also seen a couple of patches of early blight, but the septoria is doing the majority of the damage because of its early start.

Septoria leaf spot is supposed to only hit tomato plants relatively late in the year, which suggests that the fault is my own --- I probably carried the fungus over from last year's garden in my saved seeds.  In other words, any seeds I save this year will be equally suspect, although a heat-treatment of 25 minutes at 122 degrees Fahrenheit might possibly make them safer to use.

Luckily, tomato breeders are finally starting to come up with varieties that resist early blight, late blight, and septoria leaf spot.  Johnny's Select Seeds sells Jasper, a red cherry tomato with intermediate resistance to early blight and septoria leaf spot, while their Plum Regal, Defiant, and Mountain Magic are moderately resistant to late blight and early blight.

An even more enticing selection comes from High Mowing Organic.  Iron Lady is a red slicer bred by Cornell University and North Carolina State University to resist early blight, late blight, and septoria leaf spot, along with verticillium and fusarium wilts.  I'm thinking we might try all five resistant varieties next year and not use any of our saved seeds in hope of getting the various tomato blights off our farm.

Tomato planting

What's the next line of defense if that fails?  The real reason we lose so many tomatoes to blight is because our climate is very damp, even during the summer.  We already save the sunniest spots for tomatoes and don't use overhead irrigation there, plus we tie the plants up and prune away leaves close to the ground.  And this year I even tried raising the plants up on mounds to produce even drier conditions, but clearly none of that is enough to beat blight.

The next step would be blocking rain from hitting our tomatoes with a greenhouse, hoophouse, or something similar.  Or we could follow the recommendation of a Canadian website, which suggests growing tomatoes on a balcony or rooftop for a similar reason.  One of these days, I'll figure out how to have copious tomatoes despite our wet climate!

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If you need to save seeds you could try an aqueous oxygen bath, unlike bleach there are no corrosive qualities and it reverts to water after 15 minutes.
Comment by Maggie Turner Tue Jul 15 08:02:07 2014

Not sure which I have (will send a photo--it's the little dark one with a red bottom when ripe, that I brought over, Anna)--seems to be blight resistant, not sure why, tho where it is might have a bearing, between the sage and asparagus...

I guess volunteers from the compost are also blight carriers?

Comment by adianne Tue Jul 15 10:52:45 2014
Those little purple tomatoes are starting to blight, too...brown, not the yellow of the earlier blight. I think all my tomatoes are too close to shade trees.
Comment by adrianne Tue Jul 15 13:08:55 2014

@Maggie Turner: Do you perhaps mean aqueous ozone? (which is just a fancy name for an ozone solution in water).

I will readily agree that ozone is an excellent antiseptic and very suitable for e.g. sterilizing medical equipment. It is reckoned to be more effective than hydrogen peroxide and chlorine, as you can e.g. see in this paper. The reason for that is that oxygen radicals are extremely reactive. Especially with organic materials (like e.g. us!) It is actually toxic to humans. From the Wikipedia page on ozone;

Exposure of 0.1 to 1 μmol/mol (ppm) produces headaches, burning eyes and irritation to the respiratory passages.

In short, the reason that it works so well is not because it is benign, but because it is actually more corrosive than chloride!

However, ozone is not stable and has to be made on-site. In pure water, half of a 10 ppm solution of ozone in water will be gone in five minutes and it will be completely gone in 30 minutes. Unless the ozone reacts with something organic, it will revert to stable oxygen (O₂).

If you're going to use an ozone generator, best do it outside.

Comment by Roland_Smith Tue Jul 15 14:36:24 2014
Mom --- Too bad to hear the blight is starting to hit your tomatoes too! Although we've seen a bit of blight resistance in various heirlooms, I'm most intrigued by the varieties I mentioned in this post because scientists have actually determined genetic markers for resistance and, in many cases, have made sure that plants have backup genes to make them even more resistant. Hopefully that will be enough to really beat the fungi.
Comment by anna Tue Jul 15 16:06:44 2014

Heirlooms can be grafted to blight resistant rootstock, at least that's my plan for next year. "Matt's wild cherry" has always been very blight resistant for me as well.

Comment by Chris Wed Jul 16 14:21:25 2014

Chris --- Matt's wild cherry definitely keeps popping up on the internet as the most blight-resistant heirloom. I've never tried it, but should probably add it to my trial list.

I'm less keen on the idea of grafting onto resistant rootstock. My understanding is that the rootstock only resists root-borne illnesses, and since blight tends to colonize leaves, I don't think there'd be any effect. But I'll be curious to hear your report if you give it a try.

Comment by anna Thu Jul 17 14:59:07 2014

I got a used hoop-house from a friend this spring, and I have to say I never want to go back to open air tomatoes. I tried high hoops before, with about 4 feet of space at the bottom, and just a plastic roof. It was OK, but the crows still got in and destroyed most of the crop. But this greenhouse is awesome! I got red slicing tomatoes in mid June! And cherries by mid-May! And as of yet no signs of the blight which always wiped out my crops by the end of July. And my passionfruits are finally bearing fruit! Definitely get a greenhouse!

Comment by Eric in Japan Sat Jul 26 08:20:17 2014

Reading, and then thinking on the water/blight issues, I wonder if you might get yourself some creole tomato seeds. They were bred, here, by LSU, and NOLA and surrounding areas (LA Gulf Coast) are --wet--.

Worth a shot, at the least.

Comment by Anonymous Tue Aug 12 21:28:19 2014

I will be trying Jasper this year.

One tomato I can recommend for fairly decent resistance against Septoria leaf spot is Park's Whopper. Not an exceptional flavor like heirlooms, but good and a reliable cropper for me. My grandparents over-gardened their plot and didn't rotate enough so, in VA in humid wet summers, the tomatoes would get DESTROYED by blights. Park's Whopper consistently did much better than heirlooms or other commonly available hybrids.

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