Pre-harvest weed control in row crops

Farm Forum

BROOKINGS — Interesting weather throughout the 2014 spray season left some fields with more weed problems than typical and, according to Paul O. Johnson, SDSU Extension Weed Science Coordinator there is still an opportunity to keep some of these weeds from having viable seed and also help with killing the weeds to make harvest easier.

One control Johnson suggests is 2,4-D. “A growth regulator, this herbicide can be sprayed on corn after the brown silk stage,” he said. “On most labels, use the maximum rate for control of broadleaf weeds.”

Johnson explained that growth regulator type herbicides can kill or reduce the germination of most weed seeds of most weeds provided they are not fully mature.

He explained that other herbicides used for pre-harvest weed control have to be applied after the crops are mature and in the dry-down stage.

Herbicide options for row crops

Corn: The following products can be used; 2,4-D, Aim, paraquat, and glyphosate;

Soybeans: Aim, dicamba, paraquat and glyphosate; and

Sorghum: Aim and glyphosate and sunflowers paraquat and glyphosate.

“In all cases, go by the rate on the label of the product that is being used,” Johnson said. “With generic products like 2,4-D, dicamba, glyphosate and paraquat rates will vary from product to product. Remember, if glyphosate was used earlier this season and did not control all the weeds it is unlikely that it will control them now.”

Johnson reminded growers that before using any product pre-harvest they need to ensure that the chemical being used is labeled to control the weeds that are being sprayed for. “Be sure to follow all time restrictions before harvesting the crop.”

He added that if forage from the field that is sprayed, will be used for feed or bedding make sure the application does allow for this practice.

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