- Fields that experienced wet growing conditions in the spring may have been infected by Fusarium species which can cause stalk rot issues later in the season.
- This infection can develop into crown rot, which is observed as mid-late season stalk lodging.
DISEASE DEVELOPMENT AND SYMPTOMS
Crown rot infections are usually caused by Fusarium species; however, the fungus that causes anthracnose (Colletotrichum) may also be a factor.1 While the crown of a healthy plant should be a fleshy, white-green color, a tan-to-brown crown is observed with a Fusarium infection. The discoloration is reflected by the level of infection. More severe infections are darker brown, and the crown tissue becomes quite rotted. This extensive infection disrupts the "plumbing" of the plant and may cause stunting, leaf yellowing, wilting, and even death. Stalk cannibalization occurs when the corn plant is not able to complete ear fill without remobilizing nutrients and energy from lower leaves and stalks to meet the demand from the developing kernels.
The stress of wet soils in the spring is conducive for disease infection. Other stresses may include cold temperatures, soil compaction, fertility issues, or herbicide injury.2 The combination of a wet spring followed by an extended dry period can lead to crown rot infection.
While crown rot infections have their beginnings in early-season plant infections, they can persist much longer, eventually resulting in stalk rot and potential yield loss.
HARVEST CONCERNS AND YIELD IMPACT
A crown rot infection that results in stalk rot may also lead to lodging. Typical symptoms of Fusarium stalk rot include whitish-pink to salmon discoloration of tissue at the nodes, while plants infected with anthracnose tend to have shiny black blotches or streaks on the outer stalk. Fields should be monitored closely to schedule harvest while there is still enough stalk strength left to help facilitate harvest.
Fields with considerable lodging should be harvested early to minimize the risk of additional lodging. Although drying cost is a concern when harvesting wet grain, this expense will likely be a better option compared to potential yield loss from lodging. In addition, test weights may be lighter due to the impact from crown rot and/or lodging on the ability of corn to finish transporting adequate carbohydrates to the kernel.
Fusarium is a pathogen commonly found in crop residue and soil. Resistance to Fusarium crown rot is not available in current corn products. While fungicide seed treatments can help protect against Fusarium, the treatment does not persist long enough to protect corn from crown rot. Because crown rot is associated with various stresses in addition to a fungal infection, identifying and alleviating any stresses may help reduce loss from Fusarium crown rot. For example, early in the season, stunted plants with crowns that are not completely discolored and rotted may benefit from cultivation. Bringing the soil up around the crown may promote nodal root development and help the plants recover.
1Munkvold, G. 2002. Crown rot symptoms common in corn. Integrated Crop Management. Iowa State University Extension. IC-488(15).
2Munkvold, G. 2001. Crown rot affecting corn development. Integrated Crop Management. Iowa State University Extension. IC-486(18). Jackson, T., Giesler, L., Harverson, R., Timmerman, A., and Wegulo, S. Corn disease profile II. Stalk rot diseases. University of Nebraska. www.ianrpubs.unl.edu.
Web sources verified 07/25/2016.