Casaubon's Book

Preventing Late Blight in Tomatoes and Potatoes

Posted by Sharon Astyk on June 4, 2010
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Early signs of tomato late blight have been found already in Maryland, and realistically, we can expect to see it again this year. Last year for American gardeners in the east, tomato blight was a disaster. Moreover, for those of us who produce our own calorie crops, the blight on potatoes was at least as serious as the loss of salsa. What can you do to make sure it doesn’t happen again?

The first is obviously make sure you remove all potatoes that may have sprouted again. The second is to plant resistant cultivars – in tomatoes there’s some evidence that Stupice, Juliet and Matt’s Wild Cherry show resistance – and certainly home and professional plant breeders will be starting here to work on blight resistant varieties. If you are planting a late crop of potatoes for fall, consider Defender, Ozette or Jacqueline Lee, which have also shown some resistance.

It helps to stake and prune tomatoes, and allow as much air circulation as possible, and to hill potatoes as fully as possible. There are also copper products certified for organic production that can be used, but they must be applied regularly, beginning *before* infection occurs. If you plan to go this route, begin early. Most of all, watch plants closely and remove all infected plant material as quickly as possible.

There’s more information in this article on Organic Management of Late Blight from Cornell Cooperative Extension.

Sharon

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Comments

  1. #1 notedscholar
    June 4, 2010

    Given the findings of Robert Atkins, isn’t it the case that potatoes are harmful for (at least human) health? They are high on the carb index, which is associated heavily with being heavy in the west.

    So, is there a silver lining in disguise?

    NS

  2. #2 Ed Straker
    June 5, 2010

    Sharon’s readership are homesteaders who are trying to avoid a future malthusian die-off by growing their own. The last thing in the world we’re worried about is our victory gardens making us obese. It’s not being able to grow enough calories when it counts we worry about.

  3. #3 Mark N.
    June 5, 2010

    You didn’t mention that the weather was freakishly wet and overcast during the early-mid, and middle part of the growing season last year. This was the real cause of the disease breakout. So far, its looking much drier and sunnier in the northeast this year, but we are always at the mercy of the weather. No amount of cross-breeding will be able to change that. I will probably never plant those disease-resistant varieties you mentioned. Tried them, don’t like them. If I can’t have my favorite homegrown tomato and potato varieties to eat due to disease, well then at least I tried.

  4. #4 Sharon Astyk
    June 6, 2010

    6.7 billion people simply cannot eat a high protein diet all the time. That is infeasible in the extreme. Most of the world’s ordinary poor people eat a lot of carbohydrates and don’t get fat, because they move their bodies a lot. The idea it would be a blessing to lose a staple food crop is a really bizarre one, frankly.

    Mark, I think Stupice is very good, actually – and yes, the weather was a factor, but now that tomato late blight is so widely distributed, it makes it more likely that even in years not quite so wet, we may have problems. Nothing wrong with choosing to eat tomatoes only on good years, but some of us will choose otherwise. The perfect tomato is the one you actually get to eat.

    Sharon

  5. #5 Stephen B.
    June 6, 2010

    I’ve already sprayed some of the OMRI-approved copper something or other I got from Johnny’s for blight protection.

    Last year was a hellish year for those black spots that I think are peach scab. I was actually pretty good about spraying sulfur when the weather demanded it and had almost no spots. The previous year I didn’t spray, it was an ordinary dryish summer, and I had lots of peach scab, so I figure these organic fungicides actually do some good depending on the crop.

    This year our peach tree has a good fruit set. It bloomed early of course, given the crazy, warm spring and got nailed with 2 frosty nights while blooming. But I guess the sprinkler did its thing both nights. Ditto for my strawberries and cherries.

    Meanwhile, over at work, 2 miles down the road, we didn’t sprinkler-protect any of the trees while they bloomed because so many non-agricultural aspects of my work place are falling apart, it kept me inside. Over there, between 3 cherry trees, I have maybe a dozen cherries set, while 4, 5-year-old, semi-dwarf apple trees managed maybe a dozen fruit total between themselves. :-(

    Sprinkling water on frosty nights during bloom time has once and for all proven its worth to me.

  6. #6 Mark N.
    June 6, 2010

    “but now that tomato late blight is so widely distributed…”

    You apparently don’t believe that this disease occurs regularly in this region and is a common late-season problem.

    Please read this article (from ’09, I think):

    http://www.metroland.net/back_issues/vol32_no33/dining_review.html

  7. #7 Mark N.
    June 6, 2010

    Late blight is not a common early season problem. That was the weird part about last year and it dovetailed with the weird wet weather period perfectly. If we have predominantly dry, sunny weather all Summer, all late blight worries are probably gone. Given a repeat of last year’s weather, expect a repeat devastation. Late blight resistance in tomatoes, at least for now, is pretty much a joke. May as well grow what you like to eat best.

  8. #8 Dunc
    June 7, 2010

    You do know that it’s possible to grow more than one variety of tomatoes (or potatoes) at a time, right? Grow the ones you like and hope for the best, sure – but it doesn’t hurt to grow some “blight-resistant” F1s for insurance. Resilience through diversity!

  9. #9 Mark N.
    June 7, 2010

    Yeah, you can go that route. Nothing wrong with that. Don’t be too disappointed, though, when your so-called “[late] blight resistant” F1s fail along with your more tasty varieties, after putting up a bit of a fight. There no variety, to my (rather meager) knowledge, that is blight-proof. I always grow at least a dozen varieties of tomatoes, including some hybrids, so I also like diversity and disease resistance, but not at the cost of flavor. Life is short – go for the gusto, I always say.

  10. #10 Sharon Astyk
    June 7, 2010

    Again, flavor is subjective – for an early tomato, in my soils, Stupice is quite good. Moreover, tomatoes you eat inevitably taste better than ones you don’t eat. Even if they aren’t bomb proof, getting some tomatoes is better than no tomatoes if you’ve put the time and effort into growing them. Nothing wrong with preferring not to bother, but yours is not the only choice.

    And no, I’m aware we’ve had late blight around for years, but the fact is most people don’t get every single potato up, which makes it more likely we’ll have *early* late blight spores floating around this year.

    Sharon

  11. #11 Electronic Cigarettes
    March 28, 2011

    You didn’t mention that the weather was freakishly wet and overcast during the early-mid, and middle part of the growing season last year. This was the real cause of the disease breakout. So far, its looking much drier and sunnier in the northeast this year, but we are always at the mercy of the weather. No amount of cross-breeding will be able to change that. I will probably never plant those disease-resistant varieties you mentioned. Tried them, don’t like them. If I can’t have my favorite homegrown tomato and potato varieties to eat due to disease, well then at least I tried.

  12. #12 Jane
    March 29, 2011

    Comment 11 copies comment 3, that Mark N. posted in June. Advertising spam?

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