Yet, while retailers are scrambling to apply more fertilizers and spray more herbicides in 2007, they shouldn’t overlook one important fact — continuous corn can lead to some unexpected crop disease pressures. “The risk of some corn diseases is greater when corn follows corn,” says Dr. Bob Nielsen, agronomy professor at Purdue University. “This is especially true when some form of reduced tillage is practiced that leaves greater amounts of non-decomposed, inoculum-bearing residue on the soil surface.” Typically, adds Nielsen, the amount of crop residue left behind after a corn harvest is roughly equal to the weight of grain harvested from the field.
Two of the most common diseases in this case are gray leaf spot, which is typically spread by wind and rain to new leaves from leftover residue, and Northern corn leaf blight. Some of the other diseases that can thrive under continuous corn conditions include anthracnose and diplodia ear rot.
To address these disease issues, retailers need to offer their grower-customers several management plan options. In some cases, the application of a strobilurin fungicide has been able to curb disease outbreaks and increase yields. However, according to Roger Bender, plant pathologist for The Ohio State University, a more effective disease deterrent is for retailers to help their grower-customers choose better corn seed varieties.
“Basically, a good way to make continuous corn work is by selecting seed hybrids that offer better resistance to specific diseases and have good overall plant health characteristics.”