Prospects good for corn recovery

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COLUMBUS – It’s likely that significant acres of “early” planted corn were subjected to freezing temperatures last week. These low temperatures may have resulted in extensive leaf damage.

However, the prospects for recovery are usually good. Leaf destruction on small corn plants is seldom as serious as appearance might suggest.

Still survive. Young corn seedlings can be severely damaged above ground and still survive with little or no effect on yield. The key to predicting survivability is understanding where the growing point is inside the plant with respect to the stage of plant development.

The condition of the growing point is a good indicator of plant health. The growing point of a corn plant is located deep inside the seedling where all the remaining leaves originate, as does the tassel.

You can observe the growing point by digging up a seedling and splitting the stem from top to bottom. The growing point will be located at the top of the pyramid-shaped whitish stalk tissue near the base of the seedling.

In corn seedlings that have just emerged, the growing point is located about half an inch below the soil surface, just above the crown area. The growing point remains at or below the soil surface until the six-leaf collar stage, after which its position is elevated as the stalk enters a more rapid elongation phase.

Safe from frost. While the growing point is at or below ground, the corn plant is relatively safe from above-ground damage to the leaves and stem. Severe damage from late frosts, hail, anhydrous burn or insects feeding above ground will usually not kill corn plants younger than the six-leaf stage as long as the growing point is not damaged.

On the other hand, while the growing point is below the ground, the plant is more sensitive to below-ground insect feeding, flooding or saturated soils.

To determine the viability of young corn plants damaged by frost, the simplest advice is to wait for several days after frost injury for signs of regrowth. Generally 2 to 4 days of 70 degree or warmer temperatures are sufficient to stimulate new leaf growth on an affected plant.

Looking for hope. New leaf tissue should be emerging from the whorl. If temperatures have been cooler than normal, regrowth may not be readily evident. In that event, you can determine plant viability by splitting the stem lengthwise and observing the condition of the growing point.

If the plant is “healthy,” the growing point will be firm and white or cream colored. A darkening or softening of the growing point usually precedes plant death.

Subsequent rainy weather can cause problems to freeze damaged corn. Bacterial soft rots can destroy the corn growing point and this often occurs when rains splash bacteria into frost damaged leaf whorls.

If growing conditions are favorable – warm and dry after the freezing event – the plants typically outgrow bacterial damage, but if weather remains cold, wet and cloudy following the freezing event, the potential for this bacterial damage increases.

Injury from freezing can also prevent new leaf growth from unfurling normally resulting in tied leaf whorls – this frost damage sometimes resembles the “buggy whipping” and tight leaf rolling associated with certain herbicide injury.

Generally plants exhibiting such symptoms resume normal growth when growing conditions improve. Mowing fields to cut off the tied leaf whorls and thereby allow normal expansion of undamaged leaf tissue is usually of limited benefit.

(The author is a corn specialist for Ohio State University Extension.)

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