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September 2000 |
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Late Season Stalk Roots in Missouri Cornfields |
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Stalk Roots Jim Jarman |
A number of different fungi and bacteria cause stalk rots, including those that display different symptoms, including anthracnose stalk rot, diploidic stalk rot and charcoal rot. There are also general symptoms which are common to all stalk rot diseases besides discoloration of the inner corn stalk. The first sign of stalk rot, a few weeks after pollination, is usually the premature dying of bottom leaves. Eventually, the entire plant may die and appear light green to gray. Diseased stalks usually begin losing firmness during August. The cells in the interior of the stalk rot, resulting in a loss of firmness and strength. Harvest losses may be reduced if fields are scouted 40 to 60 days after pollination to check for symptoms of stalk rot. Stalk rot can be detected by either pinching the lower stalks or pushing on the corn plant. If more than 10 to 15 percent of the stalks are rotted, the lower stalks are soft or they fall over, the field should be harvested as soon as possible. Besides timely harvesting, management strategies for corn stalk rot include hybrid selection for good stalk strength and lodging characteristics, planting at recommended populations for the hybrid, proper fertility practices and talking steps to minimize plant stress, especially during pollination and grain fill. Companies provide information on stalk strength and the University of Missouri yield trials provide information on lodging for tested hybrids. The source for information used in this article is from Laura Sweets, crops specialist with the Missouri Commercial Agriculture Program and Extension Assistant Professor of Agronomy, SweetsL@missouri.edu - (573) 884-7307.
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Corn
stalk rot often
becomes evident in Missouri fields at harvest, and susceptible hybrids
can suffer yield losses of 10 to 20 percent or even more. Stalk rot
becomes a problem when plants are stressed during the grain filling
stage of development. Water shortage, extended periods of cloudy
weather, hail damage, corn borer infestation, low potassium in relation
to nitrogen, leaf diseases and other stresses that occur in August and
September may be associated with an increase in stalk rot. European corn
borer numbers were low this season in Callaway County.