tomato blight #131071 - Ask Extension


tomato blight #131071

Asked May 31, 2013, 10:02 AM EDT

Even though I've rotated my tomato plants in the garden, I've had tomato blight for several years.  This year my tomatoes will be in large pots on the deck.
What can I do to heal my garden so it will be healthy next spring?
Garden is drip watered, only has flowers pumpkins and tomatoes, diseased/dead plants removed promptly, deep rototill every late autumn, lots of sun and air movement.
Thinking of not planting anything this year but weed control (next to open space) is difficult.  Thanks, BB

Jefferson County Colorado

Expert Response

Early Blight is more of a plant tissue problem than a soil problem.  Dropped leaves are the source of the disease for the following years.  Sounds like you are doing a lot of things right to control early blight.  In Missouri, we battle early blight, too.  There is a Colorado publication on identifying and controlling tomato problems:

Here is a clip from that publication:
Early blight (Alternaria leaf spot) is caused by the fungus Alternaria solani. Symptoms become prevalent during the hotter months. This disease produces brown to black, target-like spots on older leaves. If severe, the fungus also attacks stems and fruit. Affected leaves may turn yellow, then drop, leaving the fruit exposed to sunburn. Sanitation is the best control. Remove all diseased plant tissue on the ground, as the fungus overwinters on leaf debris. Do not plant tomatoes in the same place next year. Space plants farther apart to improve air circulation. Avoid overhead irrigation. If the infestation is heavy, sulfur dust may help protect new leaves from infection.

Septoria leaf spot is less common in Colorado than early blight. It, too, is a fungal disease. Characteristic symptoms are white or gray spots on leaves, surrounded by a black or brown margin. Control is similar to early blight.

The recommendation of sulfur applications is mentioned.  We sometimes uses sprays called Lime-Sulfur or Bordeaux mixtures.  Both contain sulfur compounds and have a long history of safety.  Most garden centers will have one or both spray materials.  they have been used a long time in fruit production to control fungal diseases.
Frank Wideman Replied June 05, 2013, 11:02 AM EDT
Controlling Early Blight has to start before the disease ever starts.  Follow directions on the container, observe all cautions.
Frank Wideman Replied June 05, 2013, 12:30 PM EDT
Last posting I promise.  Link to the tomato publication:
Frank Wideman Replied June 05, 2013, 12:40 PM EDT

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