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Tips To Prevent Tomato Blight

Having a crop of blighted tomatoes is enough to make any gardener cry and maybe shout: What did I do wrong? I shall deal with tomato blight today.

But first, here’s a little cookie joke I picked up over the Christmas and holiday season.

Q: Why did the shortbread cookie cry?

A: Because its mother had been a wafer too long.

I’m always communicating with gardeners about their devotion to growing tomatoes and gardening overall. Goodwill, emails and phone calls from readers are inspiring. Let me share one letter in particular from last November that directs me to touch on a very common problem.

Betty Graham of Weyburn, Sask., writes: “Sending a picture of our tomatoes to see if you can help us out. Is it a blight of some kind?” she asks. “This happened to a lot of us in Weyburn and area.” Betty goes on to say “some gardeners started their own tomatoes and others bought plants from greenhouses. For a while, the plants were healthy.” Then it was like wham bam — as though they were stung by poisonous arrows dipped in a witch’s brew. “The plants and fruits rapidly turned dry and black and in three or four days…they were gone,” Betty says.

Let’s assume Betty’s tomato issues are a result of late blight. When such is the case, one approach is to grow bush varieties that ripen early. But keep in mind there are other variables to consider such as possible outside sources of contamination. Is the soil subjected to any form of direct or indirect residues of air pollution, acid rain, chemicals, excess fertilizer or other influences?

If we discount the aforesaid, let’s move on to blight spores and fungi that overwinter and hibernate in Mother Earth. They can remain soilborne for many years.


If all else failed you in the past, I suggest you try solarizing and compare results. Here’s how it’s done. Prepare your intended tomato-growing area sometime in April. Clear it of all plant debris. Level out the soil and then moisten it thoroughly (not mucky) with water.

Between early and late May (depending on weather where you live) cover the entire site with a sheet of fairly heavy clear plastic. Firm the edges in place with soil, bricks, stones or other objects. Keep the plastic as firm and airtight as you can so it won’t blow away. The objective is to bake the soil, during sunny daytime skies.

I know that Weyburn is one of the sunniest places in Canada, hotly pursued by others such as Moose Jaw, Medicine Hat, Osoyoos and even my own turf around Portage la Prairie. But 2009 was different. Not many of us had a lot of sunshine.

After one week, remove the plastic and till the soil lightly to bring any remaining active pathogens to the surface, then water once more. Return the plastic cover back in place as previously explained. Let the soil bake for an additional three weeks if you’re in a late-spring area, otherwise go for up to two more weeks. By the end of this period, soil is so well cooked that it’s free of diseases.


Say you didn’t solarize your soil, but have a site available that hasn’t grown tomatoes on it for at least three years. Can tomatoes still fall prey to blight? The answer of course is yes. Watch for circular spots that appear on oldest leaves closest to the bottom, then eventually turn yellow and fall off. The strategy is not to wait for evidence to progress. Hand pick and remove all diseased leaves as soon as they appear.

Next, let’s mix up something at home. Here are two formulas:


1 tablespoon baking soda (sodium


1 tablespoon light vegetable oil such as canola, sunflower or grapeseed

oil 4 litres of water


4 teaspoons household baking soda (sodium bicarbonate)

2 tablespoons light vegetable oil such as canola, sunflower or grapeseed

oil 4 litres water

4 cups skim milk


It’s best to commence initial application once transplants are established in the open garden. First time, test a small area on one or two plants and wait 48 hours to ensure there’s no untoward reaction. Experiment and select the formula that works best for your area. Apply before blight takes hold, shaking the container periodically. These formulas are a preventive measure not a cure, but they will still help infected plants. A misting is enough. It’s not necessary to drench the tomato plants.

Repeat every seven to 10 days at start of season and continue until late summer, depending on weather and health of plants. Lightly mist, covering both tops and bottoms of tomato leaves as well as stems. Do this early in the morning prior to 9 a. m., before hot sun hits. Repeat after each rainfall.

Note that some garden centres sell a light-grade horticultural oil that can be used instead of household vegetable oil when preparing these homemade recipes.

An alternate option is Bordo, a copper sulphate fungicide. This commercial product at garden centres controls leaf spots, blights and downy and powdery mildews. Follow label directions and commence spraying before symptoms appear.


…and along the pathway. They trap and prevent sneaky bacteria from splashing from soil up onto tomato foliage when it rains.

Create a barricade with a thin layer of unsprayed (no chemicals) dry or green grass clippings along the walking row and around plants. Do this every time you cut the lawn throughout summer. Or apply one inch or more of good-quality homemade compost with straw mulch on top.

Three layers of moistened newspaper between each plant is another option for trapping disease spores. Cover with two or three inches of dry grass clippings on top to firm the paper in place. Any one of these three choices can make a significant difference, or try a combo.

When buying seeds or plants, select hybrid tomato varieties that are resistant to many diseases, blights and wilts. I know there’s also great interest in heirloom and heritage tomatoes and the proactive steps indicated above will be of great benefit to them.

Eggplant, peppers and potatoes are all related to fruits of the vine and need to be kept separated. Spuds can also fall prey to the same late blight as tomatoes. To be continued…


Again, I have lots of prizes for this year’s draw. I have gardening credit vouchers that can be applied toward catalogue orders, along with seed potatoes and grape plants. More info ahead. Send your name and mailing address to me, plus any gardening tips you wish to include.

SINGING GARDENER Draws, c/o Grainews,

1666 Dublin Ave.,

Winnipeg, Man. R3H 0H1

This is Ted Meseyton, the Singing Gardener & Grow-It Poet from Portage la Prairie, Man. Cowboy wisdom says the best sermons are lived, not preached. Gardener wisdom says the heart that gives, gathers. Throw your heart over the garden fence and the rest of you will follow. My email address is [email protected]

About the author


Ted Meseyton

This is Ted Meseyton the Singing Gardener and Grow-It Poet from Portage la Prairie, Man. I salute all gardeners and farmers who help make our world a little safer and more ecologically balanced, and who toil to provide health-giving produce to others who cannot produce their own. It takes all sorts to make a world. One half of the world doesn’t know how the other half lives. The best physicians are Dr. Diet, Dr. Quiet and Dr. Merryman.



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