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Carefully check for drought-stressed cornPosted Monday, August 29, 2011, at 2:58 PM
Corn harvest has started in some local areas, mainly to crop that has suffered severe stress from the various weather conditions this summer. South of I-70 some drought stressed corn has been harvested for over a week. Yields of 60 to 75 bushel per acre have been reported. In addition to the drought and heat stressed corn, wind damaged corn has also accelerated the need to harvest earlier.
Drought stress, especially during grain fill, can predispose corn to a number of stalk rots which in turn may result in stalk lodging. Stalk rots are often the cause of lodging but there are several other factors that predispose the plants to disease infection. If you suspect that your crop was exposed to any of the following factors, you may want to look at those fields.
1. Hybrid differences in stalk strength or stalk rot susceptibility -- Some hybrids have genetically stronger stalks than others.
2. Poor root growth and other stresses -- Cool, waterlogged soils early in the season, severe drought, and soil compaction can result in small, inadequate root systems. This can result in the ears depleting the stalks, leaving them weak and susceptible to disease.
3. Poor leaf health --This will reduce carbohydrate production resulting in lower carbohydrate reserves and in turn reduce stalk integrity. Staygreen characteristics in hybrids are highly correlated to stalk rot resistance and reduced lodging.
4. High populations -- With high populations, plants tend to become taller and can result in thin stalks with inadequate strength. This is due to competition between plants for light, nutrients and water.
5.Nutrient imbalances and/or deficiencies -- Both conditions can lead to more stalk rot and stalk lodging.
6. Corn rootworm and corn borers -- Insect damage from either of these insects or other insects can provide an entry point for any stalk rotting organisms in addition to any direct yield loss.
7. Mid-season hail damage -- The physical damage caused by hail can provide an entry point for any stalk rotting organism. In addition, stalk bruising and the related internal damage may also weaken corn stalks.
Any single factor or combination of factors may affect your corn crop. If you suspect any of the factors were present in your crop, you may need to check those suspect fields to evaluate its condition. If you see increasing levels of lodging or ear drop, you may want to schedule harvest accordingly to reduce field losses.
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As our local University of Missouri Agronomy Extension Specialist, Crook has been writing a column for the print edition Agriculture page for the past three years and we will now be sharing it on our web version. Crook has a bachelor and masters degree in agronomy from University of Missouri and received his doctorate in Agronomy from Kansas State University. He was in soybean variety development research for 22 years for various seed companies and has been Saline County's agronomy specialist for 10 years.