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May 17, 2010

Tomato blight prevention tips

Memorial Day weekend is the unofficial starting line for summer and, of course, planting tomatoes.

But tomato blight, which devastated home gardens and community gardeners last year on the East Coast, has been spotted again this season in a greenhouse in St. Mary's County, Maryland, and the alarm has been sounded.

It is difficult to save a tomato plant once it has been infected with the blight - even if you spot it early and remove the infected leaves. And one infected plant is all it takes to ruin your whole crop of tomatoes (and potatoes), so here is some advice, courtesy of the University of Maryland's Home and Garden Information Center and Cornell University's horticulture department.


Blight winters over on living host material, such as the potatoes that might still be in the ground in your garden. Remove them and dispose of them in plastic garbage bags.

Remove any volunteer potato plants in your garden or compost pile. They can carry the virus.

Buy healthy plants from local growers. Learn what blight loots like and examine the plants for any signs. If you see something suspicious, alert the seller and the state extension service.

If you are planting potatoes, don't use leftovers from last year's garden or anything from a grocery store.

Blight loves cool, damp conditions and cloudy days. (UV rays kill the spores carried by the wind.) So water your plants in the morning and do it at ground level, not from above.

Inspect your plants at least once a week. More often if the weather is cool and wet.

If you find late blight in your garden, let the local extension service and your neighborhood gardeners know. Act quickly.

If you are forced to remove your plants, do it on a bright sunny day to kill of the spores that may blow around.

Late blight shows up on other plants, almost unnoticed: hairy nightshade, bittersweet nightshad, tomatillos and petunias!

If you wait until late blight shows up to use a fungicide, it will be too late. It has to be done as a preventative measure and the University of Maryland isn't recommending that just yet since fungicides can actually lead to other diseases.

Once you begin spraying, the treatments must be regular thorough. Use chlorathalonil or copper-based products and follow the directions carefully.

Consider planting potato and tomato varieties that have shown some resistence to late blight, such as such as ‘Allegany', ‘Elba' or ‘Kennebec' potatoes and 'Black Plum,' 'Matt's Wild Cherry,' 'Yellow Currant' and 'Yellow Pear' tomatoes.

"Moutain Magic' and 'Plum Regal' have also shown disease resistence and their seeds should be widely available in 2011.


Posted by Susan Reimer at 1:31 PM | | Comments (14)
Categories: Garden diseases


I have six varieties of tomatoes and the "yellow currant" has been struck with blight. I usually look over the plants daily but it has been 2-3 days and already from nothing to pretty much half the plant is spotted with concentric rings and dead lower leaves. No other plants have this issue yet and can only hope it doesn't spread as I dipose of the infection.

You are in trouble. Watch your other plants carefully and dispose of any infected ones. -- Susan

We are in Wi. 2nd year in a row we have the Early Blight. I replanted tomatoes this year in the same spot as last year. Next year I will gut out that area and put new soil in, maybe rotate plants.

Sounds like a plan to me!-- Susan

I had to turn to upside down planting in 5-gallon buckets because of blight. So far, so good.

I had blight last year (2009) we use
earth pots. we got rid of the soil and cleaned the earth pots. used new soil this year. Used tomato plants from two garden supply. plants looked very good at first. but leaves on bottom started turning yellow wit black spots. now all leaves are gone

how can I get rid of the blight from my soil? can anybody recommend/suggest any further help from a Proffesional or a store.

Whatever is attacking your tomatoes, it is not the Early Blight from the soil. It must have live tissue to winter over. If you want to get rid of whatever is in your soil, one way is to cover the area with black plastic for an entire summer and, literally, burn out the infecting spores. Or you can move your tomatoes to pots on the deck, which is what I did. They still get infected with blight late in the season, but then so do all the plants. -- Susan

listen please: never plant infected plants in the same place the next season. in fact crop rotation is a good idea anyway just to balance things out.

Help, My tomatoes are just ripening and when I went to pick a few, the bottom of the tomatoe looks like it was sucked in and is black with what looks like rot. Does anyone know what this is or how to treat it?

Check out my post on blossom-end rot today. That sounds like what you have. -- Susan

According to the information that is listed above, I think I have tomato blight. This is the first year that I've ever planted anything. I only have one tomato plant and I planted it in a large planter. What should I do? Any advice is greatly appreciated.

The good new is, you planted in a planter. The soil can be brand new next year and you can clean the container with a mix of bleach and soapy water. The bad news is, your season is over. Bag up the plants and put them out for recycling. Don't compost them. And don't let them linger. Although blight only lives on live tissue, you are asking for trouble if you leave the plants around. And, visit a local farmer's market or a farm stand for your tomatoes and know that you are keeping a farmer in business. -- Susan

Many thanks for your kind advice. I'll be sure to handle as you've mentioned above, Susan.
Here's hoping for better luck next year!!

Better luck for BOTH of us!-- Susan

We are on the Eastern Shore of Maryland. Last year I purchased cucumbers from a "big box" store and they were infected with blight. It spread to my tomatoes.

This year, I purchased cucumbers from a neighborhood store and planted them in a different location. They still got blight. I pulled them up and threw them away. However, this year's tomatoes which are the closest to where the cucumbers were are beginning to show yellowed stems and withered leaves. Can I try to prune the bad stems, bag and destroy them instead of pulling up the whole plant?

This might be a race you lose, but give it a try. Last year, I managed to keep my plants alive long enough to get a few tomatoes from them. -- Susan

This is the second summer in Northern Virginia that we have dealt with the blight that is destroying our tomato plants. Interestingly enough the hybrids seem to be more affected than the heirlooms, especially our Cherokee Purples. The plants held on long enough to produce some good fruit.We opened up another bed in another area of the yard and they fared better but still bight has affected them.

Is the method of covering the gardens with black plastic for a year really a genuine solution?

This is the second summer we have dealt with the blight that is destroying our tomato plants. Interestingly enough the hybrids seem to be more affected than the heirlooms, especially our Cherokee Purples. The plants held on long enough to produce some good fruit.We opened up another bed in another area of the yard and they fared better but still bight has affected them.

Is the method of covering the gardens with black plastic for a year really a genuine solution?

We made it through the summer with mixed reviews. I pruned (with a cup of alcohol to dip my shears in after each cut) and bagged the stems that showed blight in late July and discovered that the side of my garden facing the east was less damaged by blight. Over the summer, the sunny side too, produced most tomatoes. Blight came back but didn't ruin us. We will bag all remaining plants in a few weeks when frost hits and try again next year!

I container garden and last year ALL of my tomato plants had blight. Can I still use this soil (with newly added compost) this year? Or is the soil "tainted" and should not be reused again. Thanks, Sonja

Sonja. Two things: you should change out your container soil every year. And scrub your pots with a 10 percent bleach solution and then let them sit in it for 15 minutes. That should help prevent lots of troubles (although tomato blight only winters over on live tissue.) And check in with the University of Maryland Extensions Home and Garden information center for newsflashes on blight this year. -- Susan

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About Susan Reimer
Susan Reimer has spent 16 years writing about raising kids - among other topics - in her column for The Baltimore Sun. And every time son Joseph or daughter Jessie passed another milestone - driver's license, college, wedding or a move to a new military duty station - she has planted another garden. Now she will be writing about those gardens - and yours - here on Garden Variety.

Susan isn't an expert gardener, but she wasn't an expert mother, either. Both - the kids and the gardens - seem to be doing well in spite of her.

She lives in Annapolis with her husband, Gary Mihoces, who loves to cut his grass but has noticed that there seems to be less of it every time the kids pass another milestone.

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