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Ag Notes: Late blight found in tomatoes

June 29, 2010|By JERRY LITTLE | Contributing writer

Last summer a common call to the extension office dealt with tomato problems. Tomatoes dying seemed to be a common theme throughout the area for home gardeners. Now, we are facing the same thing this year.

On May 27, Dr. Kenny Seebold, University of Kentucky plant pathologist, confirmed a case of late blight on tomatoes from a home garden in the Northern Kentucky area. Since that first report, he has confirmed late blight cases in Fayette, Clark, Madison and now in a field location in Marion County, and it’s likely that there are more. In most years, we expect to see very little of this disease and only then at the end of the summer.

This is the second year in a row that this devastating disease of tomato has appeared earlier than expected. The main reason is that late blight has been confirmed on transplants that were for sale coming from the Michigan area. We need to be on guard and take preventative actions which is the key to controlling late blight. A regular fungicide spray schedule is the answer to late blight control.

Late blight is a fungus-like organism, and it is a fast moving and highly destructive disease of tomatoes and potatoes under cool wet conditions. Late blight epidemics in the late 1840’s were responsible for the Irish potato famine. All plants parts are affected, including fruit and tubers. Total losses are common in gardens and fields if control measures are not put in place. Early symptoms of late blight are large water soaked blotches on foliage that will enlarge and form green to brown lesions.

The pathogen will also attack petioles and stems killing the plant in some cases. Tomato fruit also will develop soft rot as well.

For the home gardener, preventive application of fungicides is necessary to prevent huge losses to late blight. In home gardens, regular fungicide application is less common than in commercial fields.

Very few fungicides are available to home gardeners; however, products such as daconil, maneb or fixed copper are the tools of choice. These should be applied regularly, and the user should refer to the product label for rates, and safety information. The products will not function well if the disease pressure is high or if the disease is already present before the spray program is started.

Control measures for organic producers are similar to those recommended for home gardeners. The OMRI (Organic Material Review Institute) has approved fungicides such as fixed copper, and sporatec for the control of late blight.

As with the protectants recommended for home gardeners, these products do not perform well under high disease pressure or if the disease is present prior to treatment. As with any product, always consult the label for rates, and safety precautions.

For more information on vegetable disease control, please contact the Boyle County Extension Service office at (859) 236-4484.

Jerry Little is Boyle County extension agent for agriculture/natural resources.

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