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Avoid Blight with the Right Tomato

January 7, 2011

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In 2009, most tomatoes grown in the eastern half of the country succumbed to late blight (Phytophthora) due to a cool, soggy June.

I live in the upper Midwest, along the Illinois–Wisconsin border, and my 'Black Krim,' 'Brandywine,' and 'Green Zebra' tomatoes were infected, too. Late blight had never been a problem previously, but we also had a chilly, rainy growing season.

Below photos show late blight lesions on tomato fruit and leaflet. Credit: Cornell University


When I lived and gardened in Texas, early blight (Alternaria solani) was a huge issue. I practiced pristine garden hygiene and mulched plants thickly to prevent the fungal spores of early blight from splashing up from the soil on to plant foliage when it rained or I watered. Late blight fungal spores, however, are airborne and invade everything that is susceptible, such as tomatoes, petunias, and potatoes. There is little defense other than chemical sprays once the fungal disease is spotted. That’s why commercial growers and home gardeners alike lost most of their tomatoes.

New Tomatoes to the Rescue

Plant breeders are offering us two methods to avoid blight damage in tomatoes this season: 1) grafted plants and 2) a hybrid bred to resist Phytophthora and Alternaria.

Any tomato variety can be grafted onto rootstock that is resistant to blight and other diseases. Asian, European, and Israeli horticulturists have been doing so for years. (Almost 95 percent of Japanese vegetables are produced from grafted plants.) Territorial Seed Company is exclusively offering several heirloom, paste, cherry, and beefsteak tomatoes grafted to 'Emperador' rootstock, which is highly disease-resistant. More companies will be bringing grafted plants to market soon.

There are a number of hybrid tomatoes bred to resist blight and other diseases. Johnny’s Selected Seeds teamed up with North Carolina State University to breed Defiant PHR, a midsize determinate tomato that is highly resistant to all strains of early and late blights. Other blight-resistant open-pollinated tomatoes are 'Santa' and 'Juliet' and 16-ounce tomato 'Legend'. 'Hefty Legend' was bred by tomato guru Dr. James Baggett at Oregon State University.

Given this year's extraordinary winter weather pattern and the climate extremes we’ve experienced in the recent past, I’ll be planting some of these blight-resistant tomatoes along with my usual heirlooms to make sure that I have a tomatoes for those first long-anticipated BLTs and salads. 

If you have comments, questions about tomatoes, or tips for a better tomato garden, please share! Just post your comment below.

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Doreen Howard has written for The Old Farmer's Almanac All-Seasons Garden Guide for 15 years and is the former garden editor at Woman’s Day as well as a photographer. She has grown more than 300 varieties of heirloom edibles and flowers in the last two decades.

In stores now!

Look for Doreen's newest book, Heirloom Flavor: Yesterday's Best-Tasting Vegetables, Fruits and Herbs for Today's Cook. Find in stores everywhere including Walmart and on the Web including Amazon.com.


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If we plant too late, we get

By Hazel Maunder

If we plant too late, we get white spots in the tomatoes, We have moved them around in the garden and that does not help. Only getting an early harvest helps to prevent this. Is there any other way to stop this problem?

Septoria leaf spot or blight

By Almanac Staff

Septoria leaf spot or blight will cause white spots on leaves and can occur during humid conditions when plants are so close as to have poor air circulation around them.

White spots on the fruit could be a bacterial canker, one of the most difficult problems to control. This, as you suggest, could come from the soil—specifically from not rotating. The thing is, avoidance is depent on rotating out the entire nightshade family. That includes tomatoes, but also eggplant and potatoes as well as peppers and tomatillos. You should avoid planting tomatoes, eggplant, or potatoes in the same soil, or each other's soil, for two to three years (some say, unequivocally, three years).

When you find a new spot for the tomatoes (and other crops, if you grow them), use rich compost and check the pH.

If you do all of this, kudos, but you still get the cankers, it could be that the problem originated in the greenhouse that produced the seedlings (you did not cite the origin of your plants). Elmination of an "industrial" problem involves sterilization of virtually everything, from tools to soil.

Perhaps it's not too late to get "new" soil for new plants and  grow them in pots.

Hi. I'd like to try planting

By PJ. Travassos

Hi. I'd like to try planting fava beans again. I've tried before but the fruit and leaves turn an awful black, shrivel and die. What is causing this? I'm kinda new at this

For the last two years,

By Nancy Fleshman

For the last two years, (Prior years were fine), my tomato plants start to die from the bottom up while still having tomatoes growing on top. No worms or bugs can be found and I mulched with straw after plants were about 2 feet tall.

Hi Nancy, If the tomatoes

By Almanac Staff

Hi Nancy,

If the tomatoes have blight we recommend that you move your plants to a different area of your garden. Crop rotation is very important in a garden so that you don't end up with soilborn diseases. Also plant blight resistant varieties if possible.

If one saves seeds from fruit

By Widge

If one saves seeds from fruit of a tomato plant infected with Early Blight will the plants resulting from the seeds be infected by way of the seeds? Thanks for your response.

I m going to plants tommatos

By arpit kumar aggarwal

I m going to plants tommatos in 20acres...which quality of plant shud i grow toearn more profit

My plants are growing like

By Peggy G

My plants are growing like crazy. On top, thick green stems and leaves but underneath, the leaves are brown and the stems are a sickly yellow. I am still getting huge tomatoes. Any idea what is causing this and what should I do to prevent this next year.
Thank you

Sounds like early blight. 

By Doreen G. Howard

Sounds like early blight.  Glad tomatoes are growing well for you.  Next season, spread a thick (3 inches deep) organic mulch around transplants when you set them out.  Avoid watering in the evening, too, so that plants are dry overnight and don't foster disease growth.

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Are there any Heirloom seeds out there that were made this way?

Branywine have a limited and

By Georgie B

Branywine have a limited and late harvest Ledend,(Juliet yellow ones),Im growing some very hardy and healthy thesolonkia but I found the secret for me is to save my seed from the healthiest plants and they by the 3rd year generaly become adapted to your climatic enviorment and growing conditions to grow well!A big factor is I put empty milk jugs with holes drilled in bottom by each plant and water the plants by filling it up!It is critical to put plants far enough apart to get good dry air circulating and spray with bakesoda&veggy oil once in awhile alternated by milk spray 9 parts water 1 part milk and keep area clean from plant debree and bag it up and trash it incase there is infeted plants with bad mold or viruses on it like blights and other plagues!Hope this helps!Also garlic water helps also 325mg asprin crushed and disolved in 1 gallon of water per adult tomato plant helps tremendously to make it healthier and more resistant to the damages of the enviorment

Heirlooms with Blight Resistance

By Doreen G. Howard

No heirloom seeds that I'm aware of, but Territorial Seed Company's grafted tomatoes include a number of heirloom varieties including Brandywine.

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