Plant Pathology Infobytes

July 2, 1996
Fast Action Needed For Tomato Early Blight

Garden vegetables are susceptible to attack by a wide range of fungus, bacterial, virus, and nematode diseases. Although diseases caused by these pests can appear anytime during the gardening season, problems tend to be more prevalent as plants approach maturity.

Check tomatoes, peppers, squash, peas, and other crops for symptoms of diseases which reduce yield and quality. Fast action could allow you to get a handle on the problem and minimize losses from diseases.

One of the most troublesome diseases for home gardeners is early blight of tomatoes. Early blight is a fungus disease which shows up each gardening season as a leaf blight on the lower part of plants. The disease moves upward and causes a "firing-up" of foliage over most of the tomato plant. Blight affected plants produce poor yields of inferior quality fruit.

How do you control early blight? Gardeners who start a fungicide application program shortly after transplanting generally don't have too much of an early blight problem. Other gardeners who've neglected spraying and have blight symptoms present on their plants face a more difficult task. However, if early blight hasn't progressed too far up the plants, it may be possible to head off the disease provided a fungicide application program is started without delay.

What fungicide should be used? Check with your garden supply dealer and select one which contains chlorothalonil (refer to the product label and statement of ingredients). Chlorothalonil fungicides are sold under a variety of trade names such as Broad Spectrum Liquid Fungicide, Fungi-Gard, Fungi-Shield, Multi-Purpose Fungicide Daconil 2787, and similar products.

Based on field tests conducted by Extension plant pathologists in Mississippi, chlorothalonil fungicides consistently provide better early blight control than other fungicides. For best results, the fungicide should be diluted according to label directions and applied at 7 to 10-day intervals for the remainder of the season. On tomatoes and most other vegetable crops, chlorothalonil fungicides have the advantage of a "zero day" waiting period from the time of application until fruit can be harvested.

For more information on other measures which should also be included in an early blight control program, stop by the county Extension office for copies of free publications.

 


Written by the late Dr. Frank Killebrew

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