Scouting is a season-long commitment, beginning before planting (measuring soil temperature and assessing condition), continues after planting (assessing plant stands and then scouting for disease, insect and weed pressure) only ending after the crop has been harvested.
Late season scouting of corn can include monitoring kernels for maturity (black layer) and moisture content and checking plants for ear molds and stalk strength.
Checking stalk strength.
Stalk rots can reduce yields. Stalk rots can decrease harvestable yield - literally leaving some ears on the ground. Corn plants are top-heavy and stalk rots increase the chance that plants will fall over (lodge) due to a combination of gravity and weather.
Conditions that favor stalk rots. Mid-season environmental conditions that favor kernel-set followed by conditions that favor plant stress increase the risk of stalk rot disease. Kernels place a very high demand on the plant for sugars. Stress reduces the rate of photosynthesis, thereby reducing the amount of sugars that the plant is able to produce. If unable to keep up with kernel sugar demand, the plant can rob sugars from other plant parts, including stalks. Many different stresses can reduce the rate of photosynthesis in the crop: too much or too little moisture; nutrient imbalances; leaf injury (ex.: hail, insects, diseases); high plant populations; and even long-periods of cloudy weather. Low stalk sugar content can increase susceptibility to stalk rot pathogens. Many of the fungi that cause common stalk rots in Illinois survive in corn residue and continuous corn and conservation tillage can increase the risk of stalk rot.
Scouting for lodging potential. Scouting for stalk rots is essential to minimize harvest losses. Begin scouting fields now or just before physiological maturity (black layer) when grain moisture is between 30 and 40 percent. Walk each field in a zigzag pattern, checking random plants from multiple areas of each field. To check a plant for stalk strength, either pinch it or push it. For the pinch test, pinch stalks toward the bottom, below the lowest node, checking for firmness. For the push test, at waist height push the plant 30 degrees from vertical to see if it returns to an upright position and the stalk remains intact (Figure). With either test, there is a significant lodging potential if 10 to 15 percent of the plants fail your particular test.
Harvesting first those fields with the greatest lodging potential reduces the chances of having to harvest lodged corn. Remember to drive slowly and harvest against the grain in lodged corn.
The next corn crop. Hybrids vary in their susceptibility to common stalk rots. Look into purchasing seed with good 'stalk rot', 'lodging', or 'standability' ratings.
Checking for ear molds.
While some of the fungi that cause ear molds can cause symptoms on husk leaves, not all do and so it is important to peel back these leaves and look at ears from multiple locations throughout each field.
Yield loss due to ear molds. Yield can be lost through smaller kernel size and lower test weights. This, along with moldy or damaged kernels, fine materials and mycotoxin contamination can result in discounts at the grain elevator.
Properly identifying ear molds is important. University plant pathologists recently produced a nice color documents that can help in identifying ear rot symptoms and offers information regarding risk of mycotoxin contamination and management recommendations.
Drying and Storing Moldy Grain. With on-farm storage, many crop producers have the option to hold onto their grain to market it at a later time. Storing diseased grain separately and for only short periods of time is recommended to reduce the chance of additional losses. Those ear molds associated with mycotoxin contamination can add additional complications to the drying and storage processes.
Agricultural engineers from Iowa State University have produced several tools that can help those interested in learning more about just how long air drying may take with a given fan and grain bin size and the crop moisture and air temperatures outside. For those that have the ability to add heat to the drying process, these experts have also produced tools that can help in factoring all of the costs associated with drying with or without heat.
Here are resources related to these topics produced by Iowa State University Agricultural Economists and Engineers:
Grain Storage - Quality Management?:
Grain Storage – Economics:
Palmer at harvest. While one would hope to have an idea about whether a field is infested with Palmer amaranth, some producers may be taken by surprise at harvest time. It is important to make preparations for encountering Palmer during harvest to avoid spreading seed of this aggressive weed species throughout the field.