Herbicide for Open Pollinated Corn

In 2004, corn producers lost 20 billion dollars due to weeds, according to a study by Iowa State University.

Weed control in corn plants reduces competition from weeds for nutrients essential for the optimum growth of the corn. The University of Illinois Extension does not recommend herbicides for corn grown in home gardens. Small farms and corn producers, on the other hand, use a wide variety of herbicide treatments to control weed growth in open-pollinated corn varieties.

Open-Pollinated Corn

Open-pollinated corn is defined as simply corn grown with no efforts to control pollination. The pollen is freely allowed to transfer to the silks of the plant from any other plant in the field. Every seed saved from open-pollinated corn produces a genetically unique plant, according to the Plant and Soil Sciences eLibrary.

Pre-Emergent Herbicides

Farmers apply pre-emergent herbicides to the soil to suppress weed germination. Early application prevents yield loss from weed competition while the corn is young and vulnerable, states the Corn and Soybean Digest. Glyphosate is one of the most popular, traditional herbicides for pre-emergent applications in corn. While considered a non-selective herbicide, meaning it kills all plants with which it comes into contact, many varieties of corn seed feature a resistance to the effects of the herbicide. Other pre-emergent options for open-pollinated corn include corn gluten meal, benefin, acetochlor, atrazine, metolachlor and atrazine.

Post-Emergent Herbicides

Once weeds have emerged from the soil, post-emergent herbicides approved for use on corn kill the weeds but do not damage the corn. Farmers spray post-emergents on the leaves of the weeds. The leaves absorb the chemicals, which work to kill the plant. The younger the weed, the easier it is to kill it using a post-emergent. Glyphosate-ready corn varieties allow for the usage of glyphosate after the corn and weeds have sprouted. Other post-emergent herbicides only for use on resistant varieties include imazomox, imazapyr and rimsulfuron. Post-emergent herbicides safe for all varieties of open-pollinate corn include nicosulfuron, primisulfuron, dicamba and 5-metolachlor.

Herbicide Resistance

Continual applications of the same herbicide or type of herbicide on open-pollinated corn crops often leads to herbicide-resistant weeds, as seen in the use of glyphosate. The need for new herbicide treatments continues to grow, despite glyphosate producing "exceptional control of many weeds," according to the 2011 Herbicide Guide for Iowa Corn and Soybean Production. The guide recommends a diverse management approach to herbicide applications, including adding additional herbicides to quickly and efficiently manage any emergence of glyphosate-resistant weeds.

References

• University of Illinois Extension: Corn
• Plant and Soil Sciences eLibrary: Corn Breeding -- Lessons from the Past
• Corn and Soybean Digest; Higher Price of Glyphosate Herbicide Makes Pre-Emergence Chemicals Cost Competitive; August 2008
• Iowa State University; Corn Gluten Meal Research Page; Nick Christians
• High Plains Journal; MANA Offers Preemergent Corn Herbicides; December 2005
• University of Wisconsin - Extension; Corn Post-Emergence Weed Control, Timing Important for 3 Reasons; Mike Rankin

Resources

• Purdue Extension Weed Science: Herbicide Families for Corn and Soybeans
• Ag Answers; Pre-Emergence Herbicides Hard to Resist; April 2006 for Weeds
• Iowa State University; 2011 Herbicide Guide for Iowa Corn and Soybean Production; Micheal D.K. Owen
• Ohio State University Extension; New Herbicides for 2011; Mark Loux