How to Eradicate Early Blight on Tomatoes (Alternaria)

If you grow tomatoes, you have almost certainly run afoul of the fungus that causes the disease known as early blight.

This ubiquitous tomato disease does not usually kill the plants, but it can greatly reduce your yield.

And even if you grow resistant cultivars, your plants still may not be completely safe. You will have to manage them carefully to keep early blight at bay.

However, there are a number of steps you can take to minimize the amount of damage that this disease can cause.

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Here’s what I’ll cover:

Early blight is a fungal disease caused by Alternaria solani. It can occur at any time during the growing season. High humidity and temperatures above 75°F cause it to spread rapidly.

The fungus overwinters in the soil, and spores can be spread by wind, water, insects, and even on your clothes or shoes.

If you catch an outbreak early enough, you may be able to save your crop. The tomatoes are still edible, particularly if the disease is mostly confined to the foliage.

You may have also heard of a disease known as late blight.

To avoid any potential confusion, I want to stress that early blight is not the same thing as late blight – the devastating disease responsible for the Irish potato famine.

Late blight is caused by a fungus-like water mold, Phytophthora infestans.

If you think early blight is bad, late blight is much worse. It is generally fatal to both tomatoes and potatoes; it can spread for miles, and it was largely responsible for the death of one million Irish people (although the reasons for that famine were highly political and not