How to Identify and Prevent Late Blight of Tomatoes

Late blight is a serious disease that may affect tomatoes and potatoes. It can rapidly destroy entire fields and ruin a farmer’s income for the year. And it may affect crops in home gardens severely as well.

You may not realize it, but you are probably already familiar with the organism that causes late blight. Phytophthora infestans was the cause of the infamous Irish potato famine of the 1840s.

For over 200 years, this organism was thought to be a fungus, but it has since been reclassified. It is now referred to as an oomycete – also known as a water mold – thanks to its ability to thrive in wet conditions.

Late blight is terminal, and identifying the problem early is critical to containing an epidemic.

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Though minor cases may be treated with fungicides with some degree of success, prevention is key to protect your plants from this disease.

In this article, I’ll show you how to diagnose a late blight infection, and how to limit the spread of the organism that causes it. I’ll also go over some methods to prevent an infection in the first place.

There are many different strains of this pathogen. Some can infect both tomatoes and potatoes, but others are specialized for one host or the other.

This disease can easily be introduced into gardens via infected tomato or potato plants. Once the plants have become infected, the organism can produce millions of spores in the right conditions.

Wet, humid conditions caused by rainfall, dew, fog, or sprinkler irrigation are conducive to the spread of this pathogen.

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