Organic Gardening

Tomato Blight: What is it, What Varieties are Resistant, and How to Prevent Blight

It’s important to learn about different diseases and pests that affect our gardens. Knowing which diseases and pests our plants are susceptible to helps to reduce the occurrence and implement preventative measures.


If you’ve been following my story, tomatoes were where it all started. Since then, we’ve always grown them in our garden. Big box stores tend to sell the same varieties. At local nurseries, there may be a little more variety. Growing from seeds though opens up a whole other world of all kinds of tomatoes. For example, did you know there are black tomatoes and green tomatoes? In my blog post What is the Difference Between Determinate and Indeterminate Tomato Plants? I talked about some of the different types of tomatoes.

“Tomatoes have so many different varieties and come in different colors contrary to what we normally see in stores. There are red, pink, yellow, purple, brown, orange, white, green, multicolored, and striped tomatoes. Each variety has an interesting name to go along with it like – Cherokee Green, Green Giant, Red Zebra, Lillian’s Red Kansas Paste, Sweet Sue, Green Zebra, Rosella Rose, and the Speckled Roman. All have their own set of characteristics, tolerances in terms of growing environments, the list goes on.If you can’t already tell,”

Learning about different types of tomatoes can be helpful depending on your climate and what diseases and pests they may be vulnerable to, like blight. It also helps to keep plants healthy in the garden!

What is Tomato Blight?

Tomato blight comes from a family of diseases that are a result of fungus-like organisms that spread through its foliage. It is particularly prominent during wet weather, heavy dew, or when humidity is 90% or higher. Blight spreads very quickly and will work its way first through the leaves to the branches, then to the fruit, eventually killing the plant. It is difficult to avoid blight since it spreads through fungal spores that are carried by the wind, insects, water, and animals that have come in contact with an infected plant.

Branch of tomato plant dying from blight
Tomato Branch dying from blight

How to Identify Blight

Blight will first begin forming on older foliage near the ground. They appear as small dark spots. Around the spots, foliage turns yellow. When the plant is severely impacted with blight, leaves turn brown and fall off or they may dry and die on the stem/branch. The fruit can be affected at any point of its maturity and have black spots. There are several fungal diseases that can be confused with blight that make it difficult to identify. An example is septoria leaf spot. This fungal disease produces tan or light gray lesions.

Spores from early blight can remain in the soil and overwinter. These spores can then infect the next crop that’s planted. Late blight does not overwinter. It needs living tissue to survive the winter.

Different Types of Blight

There are two different types of blight:

  1. Early blight
  2. Late blight

The type of blight is dependent upon the fungus that causes it and at what point during the growing season. Early blight is caused primarily by the fungus Alternaria linariae. Late blight is caused by funguses like Phytophthora infestans. Phytophthora infestans is the best known pathogen for causing the Irish potato famine in the 1840s. The Irish potato famine was extremely devastating to Ireland as it killed over a million people and caused another million to leave the country.

Tomato Blight Treatment

There are several measures that can be taken to reduce the risk of a crop developing blight. There is no way to cure the soil or plants of blight but you can use a preventative measures as a form of tomato blight treatment.

Here are some starting points for prevention:

  1. Trim the bottom leaves of the plant. By pruning off those low hanging branches, it helps to reduce pests and diseases. Remove any branches and/or leaves that do not look healthy.
  2. Allow for proper airflow by trellising, routine pruning, adequate spacing between plants. Tomatoes like a good amount of air circulation.
  3. As with all plants, avoid watering from the top of the plant. Water at the base of the plant or use a drip irrigation or soaker hose.
  4. Mulch around your plants. In our garden, we add a good layer of mulch after we’ve put in fresh soil and planted our seedlings. It adds a nice, clean look to the garden and it helps with suppressing weeds.
  5. If you’ve touched an infected plant, don’t touch other plants and wash your hands. Any tools that are used should be sanitized to avoid cross contamination. 
  6. You can try a fungicide. I do not have any recommendations for a fungicide since we grow organically and do not use any chemicals on our plants.
  7. Try compost tea! Compost tea is said to be highly effective at fighting both early and late blight. I personally haven’t tried it, but am open to trying it.
  8. Baking soda – it has fungicidal properties that can either reduce or stop symptoms of blight.
  9. Constantly work on a healthy soil environment. Although you can’t cure blight in the soil, maintaining healthy soil reduces diseases found in it.

Baking Soda ‘Blight Be Gone’ Spray Recipe

Try spraying this baking soda spray to fight blight. It only takes 3 easy steps to make it!

What You’ll Need

  • Spray bottle
  • Baking soda
  • Liquid dish soap or vegetable oil


  1. In a small bowl, dissolve 1 teaspoon of baking soda to 1 quart of warm water.
  2. Add a drop of the liquid dish soap or 2 ½ teaspoons of vegetable oil. Adding either of these will help the solution stick to the plant.
  3. Pour the mixture into a spray bottle. Shake well to mix the ingredients together.

Spray the plants to treat them for fungus. Any time treatments are applied, be sure to apply them early in the morning as it helps avoid direct sunlight. Applying treatments later in the day can cause damage to the plant.

Are There Blight Resistant Varieties?

A last option to try to avoid blight is to plant blight resistant varieties. There are blight resistant tomato plants, however, there is no guarantee that they definitely won’t get the disease. Resistant varieties are better able to tolerate the disease. On the seed packets or description of the variety, there should be an indication of blight resistance.

Examples of Blight Resistant Tomato Plants

  • Brandywine
  • Supersweet 100
  • Green Zebra
  • Roma
  • Rutgers


Can other plants get blight?

Yes, other plants can get blight. There are other types of fungi that cause different kinds of blight.  Here are some examples of blight:

  • Potato blight
  • Southern corn leaf blight
  • Chestnut blight
  • Citrus blight
  • Eggplants

Can tomato blight spread to other plants?

Yes, late blight that affects tomatoes and potatoes spreads quickly, and infect other plants too.

Is tomato blight in the soil?

Yes, blight can spread through the soil. When moisture comes in contact with fungal spores in the soil, the spores reproduce. When rain or watering hits the soil, the water splashes onto the plant, thereby spreading the fungal spores.

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