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Foliar Fungicides for Sweet Corn
This article was published originally on 6/8/1994Last year, sweet corn growers suffered severe losses to common rust (Puccinia sorghi). This and other foliar diseases, particularly Northern leaf blight (Exserohilum turcicum), can be economic problems on susceptible varieties to some extent each year. Since rust does not overwinter in Iowa, we do not necessarily expect another severe rust year, but that will depend on the weather. Although resistance is available for these diseases, it is not always completely effective and some of the most desirable varieties are susceptible. Therefore, it can be profitable in many cases to use foliar fungicides to control these diseases.
Guidelines for common rust control have been based primarily on research with susceptible varieties. They rely on scouting and consideration of relative susceptibility of the variety and weather. Similar guidelines can be used for Northern leaf blight control, although it will typically show up later in the season.
In 1993 it would have been profitable to have sprayed nearly all sweet corn varieties for rust control. Best control occurs when sprays are initiated early. Attempts to stop a rust epidemic will likely be unprofitable if the first fungicide application is made after tasseling. Last year, seed corn growers reported mixed results with fungicide applications. Some were very successful, others were disappointed. Some disappointing results were due to two factors: the disease pressure was extremely high, and many fungicide applications were made too late to effectively stop the disease.
There are four fungicides labelled for sweet corn production. All of the fungicides are effective, but some are less effective for certain diseases. They vary in the interval-to-harvest required. Check the label to determine whether or not the fungicide may be applied, rates permitted, and for any restrictions of application. Chlorothalonil (Bravo), mancozeb products (Manzate, Dithane, Penncozeb), and maneb have protective activity. Propiconazole (Tilt), a systemic fungicide, was just recently registered for sweet corn.
Year of Publication:
IC-467(14) -- June 8, 1994