Late-season issues are showing up on yield monitors as harvest gets underway. Two common things we are seeing are stalk rots and ear rots.
While the crop looked very clean at silking, many fields were hit with late season disease outbreaks such as Gray Leaf Spot and Rust. In many of these fields, the disease developed late enough that the yield impact may not be large. However in some cases the disease reduced leaf area and forced the plant to remobilize carbohydrates from other parts of the plant, weakening roots or stalks and creating conditions that lead to an increase in stalk rots.
High yield environments and large kernel sink can actually stress the corn plant. This ‘stress’ combined with high temperatures and plentiful August moisture combined to drive stalk rots — especially diplodia and anthracnose stalk rot. In the case of these late season stalk rots, often times, premature plant death causes early black layer and as a result the grain does not finish filling properly. Grain on these ears is loose and ‘rattles’ on the ear and has a lower test weight. These pathogens overwinter in corn stalks and corn residues, so manage the disease for next year by selecting resistant hybrids, maintaining balanced fertility, reducing plant stress and controling corn borer.
In addition, some areas are experiencing ear rots. Diplodia ear rot is evident in many fields with reports of significant dock on delivered grain. Growers must walk their fields and make sure they are aware of ear rot issues. It may be necessary to segregate loads so you don’t contaminate large volumes of grain or blend into on-farm stored grain. Crop rotation and fall tillage are two methods to control Diplodia, but in season, targeted application with the right fungicide can be a successful strategy. Diplodia is the result of the Stenocarpella maydis fungus taking hold a few weeks after silking – especially in warm wet weather like many of us had this August. While fungicides have existed for a while, there hasn’t really been a method of application that targets the silks and prevents this disease effectively. Utilizing new application technology that applies down in the canopy can cause a big reduction in this disease, and ultimately lead to a increase in yield.
The success of next year’s corn crop depends on your willingness to take careful notes on disease patterns from this year. Develop your 2017 disease prevention strategy before you finalize your fall tillage and make your seed selections.