Yes, Blight-Free Tomatoes are Possible!


Tomates showing tell-tale symptoms of late blight.

New strains of late blight of the tomato (Phytophthora infestans) appeared out of nowhere a few years ago, taking both seed suppliers and gardeners by surprise. This is an old disease, the one that caused the Irish potato famine in the late 1840s (other strains of the same disease attack potatoes), and we all thought that the disease was pretty much under control, since most modern potato and tomato varieties are resistant to the original strains. But the new strains that have appeared, notably US-22 and US-23, are much more virulent than the older strains and particularly harmful to tomatoes. In fact, in climates with fairly humid summers, where late blight is most prevalent, late blight of the tomato is now that plant’s most devastating disease.


Late-blight lesions on tomato leaves.

You can recognize late blight by its symptoms. First, it shows up in late summer (it’s not called “late blight” for nothing!). At first, brown spots appear on the lower leaves and grow quickly in size. White cottony growths may appear under the affected leaves… if the air is humid. The disease rises successively upwards, affecting leaf after leaf. Often stems also turn brown. Worse, just when the fruit is almost ripe, soft brown or black depressions form on it and it begins to rot. Soon it is only good for the trash.

Resistant Varieties

There are now however tomatoes with genetic resistance to late blight. Don’t panic: these are not OGMs. Natural resistance to the new strains of the disease has been found in certain tomatoes, notably wild cherry tomatoes, and has been bred into garden varieties by the same old-fashioned methods our ancestors used to create heirloom tomatoes like ‘Brandywine’ (which is terribly susceptible to late blight, by the way). Just buy and sow varieties that are resistant to the disease, and follow normal tomato cultural directives (grow them in full sun, practice crop rotation, leave space for aeration, water the roots, not the leaves, etc.) and you ought to be able to get a bumper crop of tomatoes!

20160306Defiant Johnny's.jpg

‘Defiant’. Photo: Johnny’s Selected Seeds.

  1. ‘Berry’
  2. ‘Clou OP’
  3. ‘Cloudy Day’
  4. ‘Defiant’
  5. ‘Fandango’
  6. ‘Fantastico’
  7. ‘Fantasio
  8. ‘Ferline
  9. ‘Golden Currant’
  10. ‘Golden Sweet
  11. ‘Iron Lady’
  12. ‘Jasper’
  13. ‘JTO-545’
  14. ‘Latah’
  15. ‘Legend’
  16. ‘Lemon Drop’


    ‘Fantastico’. Photo: All-America Selections.

  17. ‘Lizzano’
  18. ‘Losetto’
  19. ‘Matt’s Wild Cherry’
  20. ‘Mountain Magic’
  21. ‘Mountain Merit’
  22. ‘Mr. Stripey’ (‘Tigrella’)
  23. ‘Old Brooks’
  24. ‘Plum Regal’
  25. ‘Pruden’s Purple’
  26. ‘Quadro’

    20160306Matt's Johny's.jpg

    ‘Matt’s Wild Cherry’. Photo: Johnny’s Selected Seeds.

  27. ‘Red Alert’
  28. ‘Resi’
  29. ‘Rote Murmel’
  30. ‘Rote Zora’
  31. ‘Sun Gold’
  32. ‘Sweetheart of the Patio’
  33. ‘Wapsipinicon Peach’

Note that you still have time to sow tomatoes for this summer’s crop. You only need to sow tomatoes indoors 6 to 8 weeks before the last frost date and since that date tends to be in mid to late May in most regions (it’s about June 10th in mine!), you needn’t be in a hurry to start your plants.

Or Buy Disease-Resistant Plants

If you’re not into growing tomatoes from seed, look for tomato plants resistant to late blight in local nurseries this spring. My experience is however that they are hard to find, since most tomato growers appear to be in denial about the problem. (It always surprises me that even while their clients complain bitterly about crop failures, so many nurseries stick to old varieties they are used to and that will almost guarantee their clients will fail!) But if you know a real tomato expert (and there’s one in most areas), they’ll almost certainly offer resistant varieties.

Bring Your List

I suggest you print this list or put it on your smart phone. You’ll want to have with you the next time you shop for tomato seeds or plants.

For more information on tomato diseases, read Disease-Resistant Tomatoes.


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