- Yield Results
Foliar (leaf) fungicides are proven to arrest the development of yield limiting fungal diseases.
Fungicide application in field corn has gained popularity in recent years. Improved fungicide products in the strobulurin family (Quilt®, Quadris®, Headline® and Stratego®) and sterol inhibitor family (Tilt®, Folicur®; package mixes Headline AMPTM, Statego YLDTM) have increased efficacy of disease control. Corn grain commodity prices have increased to improve economic feasibility for applications. In addition, yield potential of hybrids is improved and increased value per acre can be conserved. This article describes multiple factors to consider for profitable fungicide application in corn.
Disease Risk Factors
Hybrid susceptibility. Corn hybrids vary in their susceptibility to major foliar diseases. Hybrids with susceptibility to disease respond better to fungicides, disease resistant hybrids do not. Fungicide response ratings (likelihood for yield protection) are listed for each hybrid in a table following this article, 9 = high response, 8 = moderate response, 7 & 6 = lowest response.
Scouting and Disease Identification
Scout corn fields in the week before tassel emergence, the time when one fungicide application is most effective. Look for lesions and signs of foliar disease. Diseases controlled are gray leaf spot, southern rust, northern corn leaf blight, southern leaf blight, northern leaf spot, common rust, and eyespot. Goss’s wilt and Stewart’s wilt are bacterial diseases and not controlled with fungicides. Information about specific corn diseases is found on LG Seeds Agronomy Web page at http://www.lgseeds.com/agronomy_resources/corn/diseases.
Usually one fungicide application is economically feasible. Best timing is just before VT (tassel) to the R1 (silking) growth stage when disease is present. Most foliar fungicides have an active range of 14 to 21 days. Applying at this growth stage is likely to protect leaves in important upper canopy leaves especially the ear leaf. Consider all disease risk factors before a decision are made, including label restrictions.
Early applications at growth stage V5 (five visible leaf collars) and V6 (six visible leaf collars) are also being advocated. Results from one application at this stage are inconclusive. Sometimes there is a yield benefit but these factors are not clearly identified. Disease pressure is low at V6. Diseases such as anthracnose are targeted but plants are infected well before V6. When one application is used the R1 application is more responsive than the V6. However, largest responses are observed when V6 applications are followed by R1 applications. So if you have made a V6 application based on disease risk then consider following with another application at R1.
Fungicide applications provide a return on investment but must be judicially used. Decisions to use a fungicide should consider factors that include hybrid susceptibility to target diseases, field history, and risk factors related to surface residue then future weather patterns for disease development. Fungicide products introduced into the market in recent years are very effective in controlling target diseases. Improved grain commodity prices are allowing better economic return for these applications, especially for susceptible hybrids in high risk fields that have surface corn residue and/or corn following corn rotations.