Gage County
1115 West Scott St.
Beatrice NE 68310
Phone: (402) 223-1384
FAX: (402) 223-1370

News Column

Paul C Hay, Extension Educator

Corn Fungicides

Corn Fungicides: Common Rust has been identified in corn fields across south east and south central Nebraska. Common rust will have more of a brick red appearance and larger pustule size than southern rust which is smaller with an orange color to it. With last year's southern rust epidemic, I've also received questions regarding fungicides.

Dr. Tamra Jackson, University of Nebraska Extension Corn Pathologist, has conducted fungicide trials the past two years at various sites throughout Nebraska. In 2005, fungicides were applied to an Asgrow hybrid at tassel in fields with low to moderate gray leaf spot pressure. Untreated plots yielded 223 bu/acre while fungicide applications of Quadris, Tilt, Quilt, and Headline yielded 225, 223, 228, and 231 bu/acre respectively. In 2006, Tamra had two planting dates which made a difference regarding the economic return of fungicide application. There was essentially no difference between the treated and untreated plots in corn planted April 18, 2006 which was similar to the 2005 results. However, because of southern rust last year, plots planted later (May 14, 2006) showed a response to fungicide treatment in five of 6 hybrids. The yield response varied from -3 bu/acre to 25 bu/acre in a very susceptible hybrid. A $2/bu corn price required a yield increase of 7.5-10 bu/acre to break even.

Some producers are concerned about another outbreak of disease this year and you don't want to risk anything with the price of corn. Many years in the past, a fungicide treatment was not economical or warranted. With minimal disease at this point this year, it's still not warranted but it is more economical. A corn price of $3 will require a yield increase of 5-7 bu to break even with a fungicide application while $3.50 will require 4-6 bu. Some companies are offering guarantees of certain yield increases when compared to check strips in the field. Here are some considerations before you apply a fungicide:

• We do not currently have adequate data to support the use of fungicides for yield increases in the absence of disease. We emphasize integrated pest management (IPM) and without adequate data and minimal disease in fields, it's difficult to advise widespread fungicide application.
• The most common foliar fungicides (strobilurin chemistry) being used on corn, wheat, and soybeans are high risk for the selection of resistant pathogens especially when used repeatedly.
• If you do choose to apply a fungicide, we emphasize the importance of leaving check strips. It's difficult to prove the benefit of a fungicide treatment if you have nothing to compare to it.

Hort Info

University of Nebraska-Lincoln Extension's "Backyard Farmer" has been helping gardeners for more than 50 years. They have developed a tomato DVD where you'll find more of their helpful, research-based information on tomato cultivars, disease, troubleshooting and more, all aimed at helping you grow better tomatoes. It can be ordered at http://byf.unl.edu or at the Extension office in Beatrice.

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