Is this tomato blight on my tomato plants and how should I deal with it?

Asked September 14, 2014, 4:01 PM EDT

I'm just now getting some signs of what looks like tomato blight on my tomato plants. I've attached a picture. Am I right that it shows blight? Should I do anything other than remove the infected leaves? The plants still have quite a bit of green tomatoes on them, and I'd like to leave them there to ripen until we get a frost. Is there anything I should do as I clean up this fall (beyond rotating the location of my tomatoes) to avoid this next year?

Hennepin County Minnesota tomato diseases lrk

1 Response

Tomatoes are susceptible to a number of leaf diseases that usually appear when fruit begins to form and become severe in late summer when conditions are favorable. In common parlance many growers refer to these diseases collectively as "blight."

The following management practices will reduce, but probably not eliminate, the damage they do.

1. Plant disease resistant varieties. Look for letters such as VNFT on the seed packet that indicate a variety's disease resistance.

2. Allow plenty of space between the plants to provide good air circulation so they dry off quickly after wetness.

3. Avoid overhead watering.

4. Spread mulch around the plants to keep soil from splashing onto the leaves during heavy rain.

5. Remove and dispose of dead and dying leaves.

6. Remove diseased tomato plants after the growing season. Do not compost them.

7. Do not grow tomatoes and related plants such as potatoes and peppers in the same place year after year. Practice "crop rotation." If tomatoes are grown in containers, use fresh soil each year.

8. Apply fungicides if the above measures aren't sufficient. Begin using them before any evidence of disease is present.

Some years conditions are more favorable for tomato diseases than others. The amount will vary whether or not you follow the recommended management practices.

By late summer the plants' energy is mostly spent. Shorter days and cooler nights slow their growth and metabolism accelerating the decline. The quality of fruit that ripens in September is usually inferior to that harvested in August.