tomato plants

Asked July 8, 2014, 9:42 PM EDT

I have had a garden for the last 25 years and have never had this problem. All my tomato plants are starting to die. First I thought it was due to cold and wet. But now it has been warm and they are worse. So then I sprayed with some soapy water, thinking it was some little bugs. I trimmed off the bad leaves, buy every day they keep getting worse. I also had problems this year with my cucumber and zucchini plants, but I think they are alright now. I rotate the garden every year and my peas and onions are perfectly fine with no problems. Thank you Lisa Knoll
701 471 0798

Burleigh County North Dakota fruits and vegetables growing tomatoes horticulture

1 Response

Hi Lisa,

I cannot be sure, but this could be late blight on your tomato (Phytopthora infestans). The lesions on the stems and the greasy lesions that initially appear on the leaves suggests this to me. I don't see any distinct rings around the lesions, which occurs with other, more common tomato diseases.

I encourage you to go to the web site http://usablight.org/ and watch a video on how to distinguish late blight from other tomato diseases. There is a test where you can trim off an infected branch, and put it in a Ziploc bag with moist paper towels overnight to trigger the white sporulation of the blight.

I encourage you to send these photos and e-mail message to Kasia Kinzer, our state pathologist for crops at kasia.kinzer@ndsu.edu.

Late blight is very destructive. Pick off infected leaves and spray chlorothalonil (Daconil, Bravo) or mancozeb (Maneb, Dithane) to protect against further infection. Keep the foliage dry when watering. Prompt action is needed since this fungus can kill plants in a matter of days.

Images of late blight can be found at Google Images. Kasia would be a good person to contact. Let me know if you have any more information.

- Tom