As this calendar year ends, crop plans are already beginning to be put in place for our 2020 season. As producers think about the upcoming year, many are contemplating a move toward more corn acres on their operations. While this move might prove to be economically beneficial to the bottom line, there are additional management considerations that need to be addressed when it comes to managing a corn-on-corn (COC) crop, particularly disease management.
Many prominent corn disease pathogens survive on infected corn residue and can be present the following growing season. Granted, just because a pathogen was present or caused challenges this year does not guarantee that it may be detrimental next year. The disease triangle illustrates this point; for a disease to impact the crop, the host, the environment and the pathogen must align (Figure 1). While all three are important components to any disease, weather conditions during the growing season can greatly affect which diseases might develop and influence their severity in a COC situation.
Seed rots and seedling blights
Seed rots and blights can affect stand establishment and seedling growth in a newly planted field. Seedling disease can occur in the form of seed rots, seedling blights and/or root rots. If the root system is damaged, slow emergence, stunted or purple plants, and stand loss can occur. Pythium (Figures 2 and 3) and Fusarium are two of the most common fungi associated with seed rot and seedling blight of corn. Rhizoctonia, Penicillium and Diplodia are fungi that occasionally cause seedling diseases. In some years, soil temperatures are low enough that seeds and seedlings are exposed to stressful environmental conditions that delay crop development. Exposure to stress can be limited by 1) delaying planting until soil temperatures/conditions improve, 2) installing field drainage to limit saturated soils, and 3) reducing plant residue through tillage. Additionally, implementing effective seed treatment options may help reduce the threat of an early season infection.
Foliar diseases during the middle of the season can have a substantial impact on yield potential. Pathogens such as Goss’s wilt (Figure 4), southern rust (Figure 5) and gray leaf spot (GLS) can be quite aggressive and can quickly reduce a plant’s leaf area, limiting its full photosynthetic potential. While some common pathogens such as Goss’s wilt, anthracnose and GLS are residue-born, other diseases such as common and southern rust are blown in seasonally by wind. Many disease pathogens at this growth stage are fungal pathogens and can be managed in a COC environment using a timely fungicide application if disease pressure is expected or is occurring. Deciding if a fungicide application is warranted depends on seed selection, crop development stage, current weather conditions and utilization of an effective scouting program. Other pathogens like Goss’s wilt and bacterial leaf streak are bacteria and not fungal pathogens. Seed selection and residue management are two keys for managing these bacterial pathogens as fungicides do not provide effective control for bacterial diseases. Knowing past field conditions and challenges can help a producer plan for potential diseases in next year’s COC crop.
Stalk and Ear Rots
Stalk and ear rots, such as Anthracnose stalk rot (Figure 6) and Fusarium crown rot (Figure 7) and Diplodia ear rot (Figure 8), toward the end of the growing season can cause harvest challenges and grain quality issues in a COC system. Many of these fungi survive in crop residue, on the soil surface and in the soil and tend to be more prolific in COC fields resulting in a higher chance of an impact on plant health and ultimately on yield. While weather can greatly impact the occurrence of both stalk and ear rots, checking both stalk and ear quality in the field prior to maturity is especially important in COC fields, so a timely harvest can be scheduled if necessary. If issues arise, prioritizing a harvest schedule can help minimize harvest losses and maintain as much grain quality as possible.
While we cannot manage weather conditions, there are cultural practices we can implement to lessen the potential impact of disease in a COC cropping system. Knowledge of field history, seed selection, tillage method, drainage, cover crops, and fertility programs are a few manageable decisions that can be critical in influencing the field/crop health of a COC system. In addition, incorporating the use of seed treatments, along with utilizing a timely foliar fungicide application, can help lessen the impact threat from certain pathogens and provide a management tool in-season to protect yield potential. By planning and incorporating different options to combat these threats, a COC system can be a profitable system and the yield impact from a given disease can be minimized.
For additional COC information, please visit Channel.com and search for agronomic information pertaining to corn on corn.
Robertson, A. and Munkvold, G. Potential disease problems in corn following corn. Integrated Crop Management. Iowa State University. https://crops.extension.iastate.edu/.
Robertson, A. and Munkvold, G. Disease management in corn-following-corn fields. Integrated Crop Management. Iowa State University. https://crops.extension.iastate.edu/.
Web sites verified 10/10/19.
Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.
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