Stand Establisment-roundup and Other Herbices: How Do They Fit?

Weed control is generally the first major decision to be made once alfalfa has germinated. Managing weeds in a timely manner is necessary to provide maximum production of high quality alfalfa hay. A poor weed management decision can lead to stand loss, poor quality hay, unacceptable weed control, alfalfa injury and a loss of money. Herbicides are applied to 75% of newly planted alfalfa in California and considered an integral part of a weed manage system that compliment cultural practices. In the last decade several new post emergence herbicides, imazethapyrPursuit, imazamox-Raptor, clethodim, and sethoxydim Prism and Poast have significantly changed weed management systems from preplant applied herbicides to post emergence herbicides expanding control of many broadleaf weeds and grasses. Roundup Ready alfalfa became commercially available in 2005 offering a new weed control system using genetically engineered glyphosate tolerant alfalfa. The impact that herbicide tolerant crops have had on other commodities is remarkable. In 2004, an estimated 70 percent of the cotton acreage, 90 percent of the soybean acreage, 65 percent of the canola acreage, and 40 percent of the corn acreage in the United States were planted with varieties genetically altered for herbicide tolerance.