Tomato anthracnose (an-thrak-nohs) is a type of tomato rot that affects ripe and overripe fruit. It’s one in a group of fungal diseases that affect s a wide range of plants. In tomatoes, the culprit is the Colletotrichum phomoides fungus.
You’ll recognize anthracnose in small, found soft spots that develop on the surface of the tomato. At first, the spots may appear as soft depressions. The circles can grow larger over time. They may even develop concentric rings. Left unchecked, anthracnose causes the fruit to rot.
At the end of the season, compact masses of the fungus (called sclerotia) survive in soil. They can remain there for to three years. Fungal spores release in wet or humid weather. They spread easily through water that splashes on plants and fruit.
The fungus is most common in ripe and overripe tomatoes – both those on the vine and those that have been picked. Only very occasionally will green tomatoes be affected by anthracnose.
Apply fungicide (following manufacturer’s instructions) when tomatoes are the size of a walnut.
Products will have the best impact when used in temperatures of 65 degrees F.
Reapply fungicide every two weeks and after rain.
In the vegetable garden, anthracnose can cause damage to beans, cucumbers, watermelon, squash, melon, and peppers.
In the landscape, anthracnose causes lesions on leaves and branches of deciduous trees, including ash, basswood, elm, maple, oak, sycamore, and walnut.
More tomato problems on fruit
By Kathy Widenhouse, award-winning writer and owner of Tomato Dirt, a leading online source for growing tomatoes and using them.
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