Corn has to survive a number of disease threats throughout the season, such as gray leaf spot, northern corn leaf blight, tar spot and common and southern rust. Managing these diseases early is essential to keeping your corn crop healthy and protecting your yields.
Management for field corn, sweet corn and seed corn plant diseases is achieved through an integrated approach of best management practices and use of foliar fungicides and fungicide seed treatments.
Knowing what these diseases look like is the first step in prevention and protection. Use our scouting guide to catch key diseases and consider using a fungicide with three modes of action, such as Delaro® Complete fungicide.
Corn Leaf Diseases
Numerous corn diseases, including those caused by fungi and bacteria, exhibit symptoms in the leaves. Fungal and bacterial inoculum can overwinter in crop residue on the soil surface and/or be spread by wind and water. Certain other pathogens must have a living host to overwinter, and spores must be carried on wind currents for new infections.
Foliar diseases that establish prior to tasseling, or become severe within two to three weeks after tasseling and pollination, can result in significant yield loss. Major diseases affecting the leaf include:
Corn Stalk Diseases
Infection by most stalk rot organisms, both fungal and bacterial, can occur early in the season. Infection, however, becomes obvious during grain fill. Stalk rots can cause significant yield loss when the disease causes plants to deteriorate prematurely, resulting in poor ear fill or light test weight grain. Lodging can also cause heavy yield losses.
Many stalk rot diseases first infect the roots and then progress into the lower stalk. These diseases plug the vascular tissue in the stalk, limiting the uptake of water and nutrients from the soil, causing a significant impact on overall yield and test weight. They are also critical because they impact the strength and vitality of the stalk; the weakened stalk can tip over and cause lodging. The occurrence and severity of stalk rot diseases depend on many factors, such as plant stress.
The stalk rot phase of corn anthracnose is distinctive. Black streaks and blotches, sometimes covering the entire stalk, appear on the surface of the lower stalk late in the season. The stalk surface usually has a glossy shine. The pith also becomes shredded, turning dark gray to brown.
Other significant stalk rots include Fusarium stalk rot, Gibberella stalk rot, Diplodia stalk rot, charcoal rot and bacterial stalk rot.
Corn Seed and Seedling Diseases
Several different soilborne or seedborne fungi in corn can cause seed and seedling rots, also called pre- and postemergence damping-off. These early diseases can rot seed, reduce emergence, slow growth and stunt plants, thereby reducing yield.
Rhizoctonia root rot can discolor and decay the outer layer of the main root and stem at the soil line and below. Rainfall, followed by cool and then warm, humid weather, is conducive to development of this disease.
Managing Corn Diseases
A well-thought-out disease-management program, including best management practices, proper seed protection and selection, and fungicide applications using multiple modes of action should be implemented to sustainably manage corn diseases.
A seed treatment provides great protection against early fungal diseases, especially in cool and damp spring conditions, and helps plant seedlings get off to a vigorous start. Also, timely fungicide applications, including foliar fungicides, help protect corn plants from fungal diseases throughout the season. For growers, a fungicide decision is a matter of considering production needs, risk management, timing of various agronomic practices and an eye to commodity prices.
What is Delaro® Complete Fungicide and how does it work?
Delaro Complete contains three active ingredients. The first, fluopyram, is a group 7, or SDHI, which has activity on important soybean diseases including white mold, brown spot and offers plant health benefits. The second, prothioconazole, is a group 3, or triazole, which has a very broad and deep spectrum of disease control and activity. The third, trifloxystrobin, is a group 11, or strobilurin, that shows preventative activity on many diseases, and also offers benefits to plant health. These powerful ingredients work together to provide consistent control of most major corn and soybean diseases and increased plant health all season long. Delaro Complete Fungicide diffuses in and on the waxy surface of the plant. It then expands protection across the plant's exterior by moving via surface moisture, such as dew. Within the plant, Delaro Complete Fungicide is transported systemically throughout plant tissue for enhanced coverage.
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