Controlling leaf diseases in seed corn in 2002
The time is fast approaching when seed producers need to be looking for early symptoms of leaf diseases in seed corn. Eyespot (Aureobasidium zeae), common rust (Puccinia sorghi), gray leaf spot (Cercospora zeae-maydis), and northern leaf spot (Bipolaris zeicola, also known as Helminthosporium carbonum) are diseases that can cause losses in seed corn production and sometimes need to be controlled with a fungicide application. In addition, Northern leaf blight (Exserohilum turcicum) seems to be making a "comeback" in some areas. The benefits of foliar fungicides on seed corn have been researched for a number of years at Iowa State University. Protecting susceptible inbreds with a fungicide has proven to be very profitable. Fungicide options have been changing; last year, Quadris (Syngenta Crop Protection) was first labeled for corn. This year, another new fungicide, Stratego (Bayer Corp.), is labeled (see June 17, 2002, ICM article). Quadris and Stratego, which both have active ingredients in the strobilurin family, offer some advantages over former standard, Tilt. Generally, Quadris, and Stratego provide superior disease control compared with Tilt and yield increases that are similar or better than those we have seen with Tilt. Three other fungicides may be used on seed corn; they differ in their type of activity (contact versus systemic), spectrum of disease control, and application requirements. The table provides some comparisons of the fungicides most commonly used on seed corn.
For now, guidelines for foliar disease control are based on scouting, relative susceptibility of the seed parent inbred, and weather considerations. We are currently researching methods to predict gray leaf spot so that fungicide application decision-making can be improved. In general, the most profitable results have occurred when sprays are initiated before detasseling. However, most of these results were obtained before Quadris was available. Given the efficacy of Quadris and the label allowing post-silking applications, there are situations in which a single post-silking application of Quadris is the best choice, depending on the scouting results. The following guidelines should be followed for the control of leaf diseases in seed corn:
Always check the label of any pesticide to confirm that it is registered for the intended use and to be sure that all label requirements are being fulfilled. Commonly used fungicides for controlling corn leaf diseases.
*If Tilt is applied after silking, crop residue cannot be fed to livestock. This article originally appeared on pages 117-118 of the IC-488(14) -- June 24, 2002 issue. Updated 06/23/2002 - 1:00pm
|