Late Blight and Tomato Seeds

“We lost out tomatoes In New York State to blight this year.   Your seed claim disease-resistant.  Are any now specifically developed for 2010 to avoid blight?

We do not use fungicides, including those claiming to be organic.

Thanks for any advice. ~S.”


Thank you for the email regarding late blight in tomatoes.  I can easily understand your concerns, as I am an organic gardener and had severe problems in my own garden this past year with it.

The most effective strategy for managing late blight is to avoid sources of inoculum (spores). For example, if you grow potatoes in your garden also, do not save potato seed from year to year. Use health-certified potato seed.  Also, only plant healthy-looking tomato transplants. Fortunately, the late blight fungus is not known to infect tomato seed.

Unfortunately no late blight resistant tomato varieties are available. The best way to combat the disease is to pick varieties that are resistant to other diseases.  For example, if you chose a tomato that is resistant to Fusarium and you have Fusarium and late blight infect your garden this year, the plant would be healthier because it would not be affected by the Fusarium (as opposed to a variety lacking said resistance that would be first infected by Fusarium and then would easily succumb to late blight.  I know from my garden this summer that I had my heirlooms go down in no time at all, but the ones like Celebrity, Goliath, and Big Beef lasted at least a few days longer and I was able to get some fruits off them.

If late blight becomes severe, remove diseased plants by digging them up. Destroy these plants immediately by burning them or by bagging them in a plastic bag and discarding the bag. These steps will help avoid production of a larger number of spores.

It is best to avoid wetting the leaves of your garden plants when you water; soak the ground around the plants instead of spraying the plants with water. If this is not possible, water your garden mid-day so that the foliage dries off quickly. Eliminate weeds around the garden so as to maximize air circulation around the plants. These practices will generally help reduce the incidence of many foliage diseases.

Tomatoes are susceptible to late blight at any time during the growing season, but the occurrence of late blight is higher in years that are cool and wet.

There is some talk that Bacillus subtilis can be used for suppression, but I admit that I have not heard too much about it.  Here in Wisconsin in the central part of the state, we have a large potato-growing region, so one tends to hear more about the latest chemical fungicide treatments that are on the market.  I’m not sure if using a biotreatment is an option for you, but if you are interested, I could pull up some information for you on it.


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4 thoughts on “Late Blight and Tomato Seeds

  1. Pingback: Late Blight and Tomato Seeds | disease database

  2. Pingback: Tweets that mention Late Blight and Tomato Seeds « Horticulture Talk! --

  3. I am a professional science generalist. I have training and interest in and exposure to a very wide range of topics. For the following reasons, I expect this next summer to be wet and cool in much of the northern hemisphere.

    1. So far, as of Dec 26, the expected ENSO (El nino) is not building.

    2. The very deep solar minimum (~11 year cycle) only recently show signs of some revival.

    3. El Mayon Volcano in the Philippines is entering an eruptive phase producing thousands of tons of sulfur dioxide gas per day which will produce a reflective layer in the atmosphere making it cooler.

    4. Continued increases in greenhouse gases are producing more warming and evaporation supplying more moisture to weather systems.

    5. For North America, this means an increase in the number of storms also.

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