Fight Tomato Blight

Learn to combat that tricky tomato blight.

By Doug Oster


Summer 2012

Tomato Blight

There are options when it comes to fighting tomato blight, from fungicides to planting a more resilient variety of tomatoes.

Photo by Fotolia/kingan

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Q: Each season I get some kind of blight on my tomatoes regardless of where in the garden I’m planting. I love tomatoes and always harvest some, but wish my plants looked better, especially at the end of the season. Any ideas what I can do? — Steve in Indiana

A: You’re not alone. Many gardeners are perplexed when continually struggling with tomato fungal diseases. One of the worst things that can happen to a tomato is contracting late blight. It usually starts with the stems turning black, then the leaves and finally the fruit. Nothing can save a tomato from late blight; it must be bagged, burned or buried. Thankfully, late blight is not nearly as prevalent as other less-tragic fungal diseases.

The key is always identifying the problem. I’ve seen way too many gardeners destroy their crop thinking they have late blight when actually dealing with early blight or blossom-end rot. Get online and figure out what you’re dealing with for sure. (Editor’s note: If you Google “tomatoes + the name of whatever problem you suspect” and click on the Images tab, you will get loads of photos of that particular problem. Compare to what you have and make a diagnosis.) 

Beating fungal diseases often depends on the weather. For the gardener it means being in tune with the season. If the early part of summer is cool and wet, tomatoes will almost always contract fungal diseases. Prevention is the key. With those conditions, the best way to deal with the diseases is to spray the plants with an organic fungicide before seeing signs of damage. Once the fungal issue begins, it can be managed, but never as well as when treatment begins early.

Even though copper-based fungicides are approved for organic gardeners, I prefer biological fungicides like Serenade. It attracts the spores themselves, preventing them from multiplying. Giving tomato plants room to breathe will help. Plant them on 3-foot centers at the closest and grow them up on stakes or in cages. Use thick mulch at the bottom of the plant which stops soil-borne fungal diseases from splashing up on the bottom leaves. Early blight is evident when leaves turn yellow on the bottom, and then progressively work to the top of the plant. 

Grow different tomato varieties; some will be more disease resistant than others. There are tomatoes that are bred to fight off fungal diseases. By planting different types, chances of harvesting for a long season are greatly improved.

My favorite tomato varieties are ‘Caspian Pink,’ ‘Mortgage Lifter,’ ‘Rose de Berne,’ ‘Cosmonaut Volkov,’ ‘Stupice’ and many more. They all react differently to fungal diseases, but are tough and produce reliably. Just because I like these, doesn’t mean they are for you. Experiment and keep trying something new to compliment your favorites.