Freeze, then rain, tough on corn crop


COLUMBUS, Ohio – In Ohio some farmers recently reported soils freezing to three-fourths an inch below the surface – enough to damage a plant’s growing point, said Ohio State University agronomist Peter Thomison.

Above ground, subsequent rains are cause for worry, Thomison said. Rain can set corn plants up for an early death from bacterial soft rots. Rain can splash soil bacteria up onto seedling tissue injured by the freeze, providing an opening for infection, he said.

“Usually, the plant can outgrow tissue damaged from freezing temperatures,” Thomison said. “But if it stays wet and cold, the plant can’t outgrow the bacterial damage.”

Don’t rush to replant.

An advantage is that wet weather prevents farmers from prematurely replanting their fields. Some farmers might be overanxious to replant at the first sign of frost damage, Thomison said. Plants might recover, anyway, given enough time.

Leaf injury from freezing can inhibit normal leaf unfurling, resulting in “tied leaf whorl syndrome,” or “buggy whip” syndrome. It often looks almost like herbicide injury, Thomison said.

“Sometimes farmers are tempted to mow these fields, but generally this is of limited benefit,” he said. “Plants with tied whorl injury often resume normal growth when growing conditions improve.”

What to check.

By the time fields dry, farmers will be able to properly assess fields for replanting. Check plants by splitting seedlings lengthwise. A white, firm tissue is healthy. Soft and green-to-brown color tissue indicates plant death.

“The good news is there is still plenty of time to replant,” Thomison said. “By planting early, you can still have time in the season to optimize good yields if replanting is warranted.”

The late April freeze might push some farmers into a mental game of Monday morning quarterback, imagining they could have avoided damage by delaying planting a few days. But it’s usually best to err on the side of planting early rather than hope for sunshine that might never come, Thomison said.

Generally, the worst that can happen from early planting is stand loss from early weather stress, he said. Farmers can compensate by overseeding 5 percent to 10 percent of the normal rate. Between April 15 and May 1, farmers can resume normal seeding rates.

Corn may lose yield if planted 10 days to two weeks before the optimum planting period of April 25 to May 5, Thomison said. However, an early-planted crop will generally yield more than one planted two weeks or more after the optimal period, he said.


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