By Matt Hutcheson, CCA, Product Manager, Seed Consultants, Inc.
With warm, wet weather occurring across the eastern Corn Belt, now is a critical time to begin scouting for disease and determining whether or not fungicide applications are necessary. Over the last week our agronomy and sales staff and observed Gray Leaf Spot(GLS) and Northern Corn Leaf Blight (NCLB) developing in our sales footprint. The fungi that result in the formation of GLS and NCLB overwinter on corn residue. The development of these diseases depends on environmental factors. Warm, humid weather favors growth of GLS and NCLB. Periods of heavy due, fog, or light rain will provide the needed conditions for these leaf diseases to develop.
Scouting this time of year is critical to determine what diseases are present and the severity of disease. Taking time to walk fields will allow growers to make sound management decisions based on observations. When determining where to start scouting, growers should determine which fields are most at-risk for disease development. Fields where disease development is most likely to occur and will most likely respond to a herbicide include the following factors: have a history of disease development, are in continuous corn production, and are planted to hybrids susceptible to disease.
When determining whether to spray, several factors must be considered. First, consider the severity of the disease. If moderate to heavy disease pressure is present and moving up the plant to the ear leaf or above, a fungicide should be considered. The upper canopy of the corn plant plays a significant role in yield production and protecting those leaves is critical. In what stage of growth is the crop? Moderate to heavy disease pressure prior to tasseling can lead to significant yield reductions. What level of disease resistance does the hybrid have? In general, it is not recommended to apply a fungicide to hybrids with above average resistance to disease. However, seedsmen have observed significant GLS development in hybrids with excellent disease resistance this year in continuous corn fields. What is the expected yield benefit from a fungicide application? Will it outweigh the costs? In Seed Consultants testing, certain hybrids will have a significant yield response to fungicides while others will not. Fungicides should only be applied when an economic benefit is expected.
Taking into consideration all the factors that determine if a fungicide application is warranted can be a daunting task. Seed Consultants knowledgeable sales staff and agronomists are available to help customers determine when fungicides are needed.
For more information on disease and fungicides in corn check out these links:
Fungicide Efficacy for Control of Corn Diseases
When to Consider Foliar Fungicide
Applications on CornFoliar Fungicide Application in Field Corn – A 2014 Update