April's Ag Advice by April Borders Corn harvest is just getting underway but there are some fields of corn where growers may want to harvest sooner than they had planned. Stalk rots (fusarium, anthracnose, gibberella, diplodia, etc.) have infected some corn fields and could impact harvest and harvest losses.
Stalk integrity in some of these fields is starting to decline. To reduce potential harvest loss due to stalk lodging, growers should start scouting their fields and check stalk integrity. This can be accomplished by a couple of methods. One method is to simply pinch the lower portion or base of the corn stalk on 20 consecutive plants in five areas of the field. If the stalk collapses or feels soft, stalk rot is indicated.
Another method is to push the plant over about 12 inches at the ear level. If the stalk collapses, stalk rot is indicated. Fields that have more than 10 to 15 percent of the stalks exhibiting stalk integrity issues should be scheduled for early harvest.
Growers often talk about taking corn out of the field at 18 percent or less moisture; however, potential harvest losses resulting from waiting for the corn to dry down to this figure can be severe. To minimize harvest loss issues, consider harvesting fields with stalk rot at moistures around 22 to 25 percent.
Stalk rot infections are related to stress and factors that reduce the amount of photosynthate (sugars and carbohydrates) produced by the plant. As kernels develop, they pull carbohydrates from the stalks and roots. When corn plants are stressed, the carbohydrate demands by kernel development is often greater than that being produced by the plant. When this happens, the kernels take priority and tap the stalk and roots for their stored carbohydrates, thus predisposing the corn stalk and roots to stalk rot infections and deterioration.
Examples of various stresses that may trigger stalk rot issues include: cold, wet conditions, drought conditions, prolonged cloudy weather, nutrient deficiencies, insect damage, hail damage, wind damage, compaction, loss of green leaf tissue due to leaf spots, rust and/or other corn leaf diseases, high plant populations, high yield potentials, etc. When conditions favoring high potentials and high kernel numbers per ear are followed by any of these stress factors, stalk rots are often common as the plant just can't keep up with the carbohydrate demands of the developing kernels.
The only thing that you can do this year is to schedule your fields for early harvest. But what can you do to prevent this next year? While it is impossible to control all the various stress factors that can predispose the corn crop to stalk rots, there are a number of sound risk management practices that you can incorporate into your production plans.
* Genetic diversification � plant corn hybrids of different genetic background, this way you can better manage risks from a wide range of environmental issues.
* Proper planting populations � planting populations should vary with hybrid, soil type and even somewhat with planting date and nitrogen fertility level.
* Insecticide usage � insects injure the corn and open a pathway for stalk rot organisms to enter the plant. By controlling various soil as well as foliar insect pests, the risk of stalk rot can be reduced.
* Proper fertilization � a thorough understanding of the crop nutrient status is essential for optimum corn growth and development. Obtaining a current soil test of your fields is a good starting place. While all plant nutrients are important, stalk rot issues often occur where potassium and/or nitrogen are limited.
* Effective weed control � weeds compete for space, water, nutrients and light and must be controlled to prevent added stress to the corn crop. Knowing the weed pressure within the field is very important for proper herbicide selection. All herbicides should be applied in a timely manner to obtain maximum effectiveness and minimal crop stress.