Bad Blight #130884 - Ask Extension


Bad Blight #130884

Asked May 30, 2013, 2:36 PM EDT

I got blight on my tomatoes last summer and it traveled to most of my garden. I was told to not do a garden for a year.Is that true or is there anything I can plant that will not be affected by the blight this year?

Weld County Colorado

Expert Response

Early blight controls must happen before the disease appears and multiple applications are almost always needed.  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. For that reason, some benefits may come from not planting tomatoes for a year.  Controlling the leaf litter and spraying for the disease may be a better solution. 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.  
Follow directions on the container, observe all cautions.
Frank Wideman Replied June 05, 2013, 12:42 PM EDT

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