Talking about stalk rot before the calendar turns to April may seem like an early April Fool’s joke, but it’s not. Dave Nanda, consultant for the Corn Illustrated project, strongly believes that any kind of stress during the growing season can set the stage for stalk rot near the end of the season. Stress can include planting too early, working wet soils and creating soil compaction, planting too thick, dropping nitrogen rates too low so that the crop runs out of nutrients later in the season, and a whole host of other factors that prevent corn form performing at top efficiency.
In the first year of Corn Illustrated plots, Nanda and the Corn Illustrated staff saw a graphic example of how stress results in the opportunity for stalk rot. In the high-yield plot, one section was not irrigated. The soil was underlain with gravel, and about half normal rainfall fell during the season, timed poorly for good growth. To make matters worse about 40 days of temperatures of 90 degrees F or higher cooked toe crop. Part of that high yield plot was at 32,000 plants per acre, the other at 41,000 plants per acre. Lodging in both populations in the highly-stressed, non-irrigated part of the field topped 30%. Where corn at the same population levels was irrigated, lodging was very near zero at both populations.
The stalk rot that took over in the non-irrigated corn in that plot last year was anthracnose stalk rot, Nanda notes. It thrives upon situations where some other factor ahs created stress within the corn plant. Coming in relatively late in the season, anthracnose stalk rot resulted in discoloration of stalks, and left tell-tale grayish, blackish spots behind on the stalks. In contrast stalks from irrigated parts of the same field that were not stressed so severely were still bright and virtually free from stalk rot at harvest in mid-October.
“This was a classic case and a good example of the damage that stalk rot can do,” Nanda says. There are other stalk rots besides anthracnose that can invade corn once it’s been exposed to excessive stress. Anthracnose stalk rot is common to many parts of the Midwest, including central Indiana where the plot is located.
Weather is the one factor that you can’t control, Nanda notes. That makes it even more important to properly manage the factors you can control to limit stress, he notes. That includes picking seeding rates matched to conditions, providing ample fertilizer for plant growth and planting under suitable conditions. Continue with scouting during the season to make sure diseases or nutrient deficiencies that might be correctable don’t wind up stressing the crop late in the season, he concludes.