Reports have been coming in regarding corn that is stunted and showing uneven growth. There are many potential reasons for corn to be stunted this year in Illinois. The list of possible reasons includes herbicide damage, sub-optimal fertility, soil compaction, wet/flooded conditions, dry conditions, insect damage, cool weather, root diseases, and other factors. Some of the causes are poorly understood. The purpose of this article is to remind you of factors that influence stunting and uneven growth, and to focus on disease that may cause these effects at this time of the year.|
Observing the pattern of the problem in a cornfield is key to determining the cause. Soilborne pathogens, such as Fusarium and Pythium, tend to be scattered in patchy distributions in fields, often in association with old infested roots and plant debris. This fact can sometimes be related to scattered root infection and uneven growth. If you have been reading the Bulletin (issue no. 6, May 4, 2001) this year, you already have read about nematodes and how they can cause stunting and other problems for corn. Although other pathogens are more often recognized on corn, nematodes may be a hidden problem that is bigger and more widespread than is often acknowledged.
A primary cause for much of the uneven and stunted growth this year may be due to root rot diseases, in combination with the unusually cool weather we had a few weeks ago. Root rot pathogens of corn are common in many soils, but it often takes another stress factor, such as excessively cool or wet conditions or nutrient stress, before they cause problems.
Rotation out of corn is the key preemptive management strategy, and tolerant hybrids may be of value for minimizing fungal infections, but there are few management strategies that can be implemented at this time of the year for root diseases. The recent warm weather along with continued seasonal temperatures may allow some plants to still recover this season.--Dean Malvick