The 2011 growing season got off to a slow start as wet weather and cold soil delayed corn planting across the Midwest. This has left many growers wondering if a foliar fungicide is still necessary for late-planted corn.
In most cases, the answer is yes. The chances of foliar diseases and stress developing in corn can increase with later planting, resulting in an even greater benefit from using strobilurin fungicides
When a foliar disease infects a corn plant in its early reproductive growth stages, it increases the chance there will be a negative impact on yield. Disease infections are more likely to occur in the warm and humid summer days, so when corn is planted later, corn will hit its immature growth stage during this high-risk time. Some diseases, including gray leaf spot, northern corn leaf blight and rusts, are most destructive when established in plants at or before tasseling, which is likely to happen when corn is planted late.
Northern corn leaf blight tends to enter fields later in the season, often only causing minimal yield loss when corn is planted on time or early, as in the 2010 season. However, this disease can be extremely harmful if it strikes when plants are still in the immature stages of development. According to the Compendium of Corn Diseases published by the American Phytopathological Society, if northern corn leaf blight “is established before silking, losses in grain yield of up to 50% may occur. If infection is moderate or delayed until six weeks after silking, yield losses are minimal.”
The risk of gray leaf spot infections also increases when corn is planted later in the season, according to studies by the University of Illinois Extension.
Other diseases, such as common and southern rusts, may also infect corn during earlier stages of development before resistance to these diseases has been established.
Even in the absence of disease, using a strobilurin fungicide
in the early vegetative stages or at the R1 growth stage
improves plant growth processes and reduces the impact of environmental stress, resulting in physiological plant benefits
. The high price of corn and the odds of disease risk increasing with late planted corn means a more profitable return on investment with the use of a fungicide. So protect your crop and your wallet with a well-timed fungicide application.
Eric Tedford, Fungicide Technical Brand Manager for Syngenta, provides technical leadership for the development of fungicides. His experience includes fungicide research and development for field crops, development of postharvest fungicides, and global technical development of fungicides. He holds bachelors, masters, and doctorate degrees in plant pathology from the University of Massachusetts, Clemson University, and the University of California (Davis), respectively.