Corn farmers shouldn't be overly concerned if they suspect herbicide damage in newly emerged fields, says a University of Missouri weed scientist.
"We're getting substantially higher than normal reports of buggy-whipped or partially unfurled corn seedlings – a sign of damage from chloroacetimide herbicides," says Bill Johnson, extension weed specialist. "But as long as the plants are green and alive, and the corn stand isn't reduced from other factors as well, that damage alone isn't a reason to replant."
Johnson says he annually gets a few phone calls about such damage, which is related to cold, wet growing conditions and the use of most soil-applied pre-emergence herbicides. When cold and wet, corn plants grow slowly, and they are unable to process the small amounts of herbicide they take in with soil water. Effected plants will be twisted, with leaves failing to unfurl from the stalk. The plant resembles a tiny buggy whip. Under good growing conditions, corn typically tolerates herbicide intake.
This spring, much of Missouri north of Interstate 70 has been extremely wet. "We had a period of very cool weather in mid-April, and a lot of rain, and symptoms are now showing up," he says.
"As long as there's an adequate stand, and the plants are still green and growing, they will come out of it and yields should not be hurt," Johnson said.
For detailed information on corn and soybean replanting decisions, contact your local Extension office or check the MU Ag Guide 4091, "Corn and Soybean Replant Decisions." The guide sheet is available from the World Wide Web at http://muextension.missouri.edu/xplor/agguides/crops/g04091.htm .