tomato blight

Asked August 31, 2017, 8:05 PM EDT

My sungold that is growing in a raised bed has what the extension service believes is blight. How do I take care of the soil for next year's crop? I won't be growing anything in it over the winter, unless you advise a cover crop. It will be very difficult for me to remove the soil but I will do it if necessary. Thank you, Kate

Lane County Oregon vegetables tomato problem

3 Responses

What kind of damage are you referring to when you say the plant has tomato blight? “Tomato blight “can be a generic way meaning the plant has leaf problems. Or it can refer to one of 2 different diseases. Late blight is most common during the summer and is triggered by rainfall which deposits wind-borne spores on the leaves. Early blight is spread by wind-borne spores that survive the winter on volunteer tomato, pepper, and/or potato plants. These diseases affect leaves in specific ways shown in the links, below.

Both diseases are held in check by warm dry weather. So, because of the recent series of consecutive heat waves here in the northwest, I wonder if the problem is due to something else. You might consider uploading several images when you reply to this email. The most useful are three: One of the plant and its surroundings; another of the plant, alone; and a close-up view of typical damage.

If one of the diseases is present, the most important thing to do is to remove and discard every bit of plant debris. (Do not compost it!) No need to remove or replace soil.

See “Understanding Late Blight of Tomatoes” (http://extension.wvu.edu/files/d/21601b2f-ce49-41ed-b046-c88196789ce2/late-blight-of-tomatoes.pdf) and “Early Blight of Tomatoes” (http://www.extension.umn.edu/garden/fruit-vegetable/plant-diseases/early-blight-tomato/).





I sent images. I suspect that I had more than one disease process going on. I also had what looked like gnats along the stems of my plants and one plant was very sticky. I have 3 sungolds, but only one in a raised bed, the others are in containers. Thanks.

Images sent to the Extension Service offices do not also arrive at Ask an Expert. However, the 3 you attached to this response did arrive.

The plant the container ran short of water, one or more times. That was mostly due to a combination of factors: A large vigorous plant in a relatively small container plus rapid drying of the potting mix during the recent, and continuing, heat waves. The goal is to maintain an evenly moist root zone. Container-grown plants may require water 2, or even 3, times every day.

To grow tomato in a container, choose a compact kind and plant it in a 10-gallon, or larger, container. Larger is better.

What appeared to be gnats on the stem were likely aphids, common small squishable pests in gardens and landscapes. One remedy is to squish them when they get out of hand. Or blast them off the plant with a harsh water spray early in the day. If a pesticide is preferred, the safest one to use against aphids is a commercially prepared insecticidal soap applied directly to the aphids and repeated according to label directions. Never apply any pesticide for insects or diseases if temperatures are above 85F or will go that high later in the same day.

The other 2 images are challenging to decipher. If their problem is late blight, the affected parts of leaves and stems will show a fuzzy white fungal growth on what appear to be water-soaked tissues.

Late blight is assisted by summertime rainfall as well as overhead watering, from either a sprinkler or hand-held hose.

If the plants have late blight, they may now be dead or nearly so. No point in trying to save the tomatoes, either green or red, as they are already infected and will begin to rot within days. Fungicides won’t help at this late stage. Remove and discard the plants as well as every trace of debris that remains.

This publication may provide additional insights: Grow Your Own Tomatoes and Tomatillos (https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec1333.pdf).

If you have more questions, please ask.