Tomato – Late Blight Identification

Q: My Rutgers tomatoes are showing brown spots starting at the stem end, rapidly coalescing and moving downward towards the blossom end of the tomato. They are all green tomatoes which are not starting to ripen yet. Is this late blight?

A: I think your diagnosis is correct; late blight symptoms are particularly noticeable on green fruit.

See these pictures.

Late blight fungus lives in the soil and on infected plant residues. Soil drenches don’t control this fungus. Unless you can plant non-tomato plants (beans, corn, squash) in your tomato patch for three years, you’ll have to use fungicide sprays to control late blight each year.

Alternate sprays of chlorothalonil (click for sources), copper (KopR Spray, etc) and mancozeb (Bonide Mancozeb, etc) every week according to label directions.

If you can’t rotate your crops or spray fungicides you’ll have to buy your tomatoes at the community farmer’s market.

At this point I don’t think the plants can be saved and I think the fruit will not taste good.

tomato late blight

tomato late blight

tomato late blight

tomato late blight

tomato late blight

tomato late blight

Tags For This Article: , ,