Temperatures dipped below freezing in many areas of the Corn Belt over the past several days, with freeze warnings issued in many areas, causing many to worry about recently planted or emerged corn plants.
Yield loss due to early season frost is related primarily to stand loss, not leaf damage. Most plants will recover from early frost, making replanting unnecessary. However, if plant populations are reduced significantly after a four-day waiting period, replanting may be necessary.
The extent of crop injury from low temperatures or frost depends on the specific temperature range experienced. Lethal cold temperatures are at or below 28°F, while a simple frost occurs at temperatures above 28°F. Corn can often survive a simple frost if the seedling’s growing point is not affected. The growing point, where new tissue originates, is located below ground until the plant reaches V5. To locate the growing point, dig up a plant and split the stalk lengthwise from upper leaves through the root crown. A healthy growing point is firm and white or yellow in color. A damaged growing point will be watery and orange or brown in color.
Wait three-to-four days after frost to determine the extent of the damage, especially if the growing point was at or near the soil surface at the time of the frost. To get an accurate estimate of damage, observe plants from at least three parts of the field.
Frozen tissue usually turns silver approximately four-to-six hours after temperatures return to normal. Leaf tissue becomes dark and water-soaked, then brown and dry. New leaves should emerge from the whorl within three-to-four days if the growing point is uninjured.
If you have performed stand counts prior to the recent freeze, take new counts and compare the numbers to determine if replanting is beneficial.
If fields were planted 24-72 hours prior to the freeze, germinating seeds may suffer from imbibitional chilling, where seeds imbibe water and cell tissues get too cold, causing them to rupture and leading to potential germination failure. Monitor any fields planted in the three-day window prior to a lethal freeze or simple frost to determine if replanting is necessary.
For additional support, reach out to your AgVenture Yield Specialist to determine the best course of action moving forward.1