Introduction of Glyphosate-Tolerant Sugar Beet in the United States
Sugar is produced mainly from sugarcane and sugar beet, and is ranked second worldwide in terms of production after the combined harvest of maize, rice and wheat. World annual sugar production is about 165 million tonnes, with 26% coming from sugar beet. The US uses about 12 million tonnes of sugar annually and typically imports about 15% of its sugar requirement from trading partners and produces 85% of its needs internally, with 44% obtained from sugar cane and 56% from sugar beet. California, Oregon, Idaho, Washington, Michigan, Wyoming, Colorado, Nebraska, Montana, Minnesota and North Dakota are beet-producing states, the latter two states contributing 56% of the total beet-sugar production. One of the major factors limiting sugar beet production worldwide is weed control. Since sugar beet is a low growing crop, most weeds overtop the sugar beet plants and will cause significant yield reduction if not controlled. Conventional herbicides have been used since the 1950s as the primary method for sugar beet weed control, but can cause some damage to the crop because of marginal selectivity. Over the past 30 years, 'weeds' were consistently listed by growers in Minnesota and North Dakota as their most important problem. In the US, weed control programs for conventional beet requires three to four applications of several herbicides, often as tank mixes, along with one or two cultivations. The average cost for weed control in conventional sugar beet in Minnesota and North Dakota was about $226/ha in 2008. In western states such as Wyoming and Colorado, weed control costs for conventional beet ranged from $171 to $319/ha. However, in some areas such as Worland and Lovell in Wyoming, weed populations were generally high and control was not always acceptable even with full rates of conventional herbicides, probably because of the dry environment. As such, growers in these areas had to employ labour to weed beet fields, resulting in weed control costs reaching $437/ha. Monsanto (USA) and KWS SAAT AG (Germany) patented Roundup Ready Event H7-1, which gives tolerance to glyphosate (GT), after introducing Agrobacterium sp. strain CP4-EPSPS into a proprietary multigerm sugar beet line. After several years of testing GT sugar beet in commercial fields, widespread commercial production commenced in 2008 when it was marketed and grown in all of the sugar beet growing states except California. In 2008, Idaho growers planted 98% of their crops with GT sugar beet, Wyoming, Nebraska and Colorado growers cultivated 85 to 90%, Michigan had 55% and those in North Dakota and Minnesota planted 50%. In 2009, with increased availability of seeds, more than 85% of the production nationally is with GT sugar beet. The remaining areas are planted with conventional varieties that have resistance to specific pests or diseases that are not yet commercially available with the new technology. For example, some growers in North Dakota and Minnesota used conventional varieties that had good resistance to Rhizoctonia root rot in fields with a history of this disease. In Michigan and Idaho, fields with a history of sugar beet cyst nematode, Heterodera schachtii, were planted with conventional varieties with proven tolerance to nematodes. In 2008 and 2009, all growers paid a fee of about $158/ha ($106/100,000 seeds) for using GT sugar beet. In addition, growers paid about $14/ha more for GT sugar beet varieties compared to conventional varieties. Most growers use two applications of glyphosate to provide excellent weed control. Growers also cultivated once in 2008, mainly to assist in drying wet fields. Weed control costs using two glyphosate applications and one cultivation in GT crops was estimated at $92/ha. Growers in states such as Minnesota and North Dakota incurred an average additional cost of about $38/ha using GT sugar beet compared to conventional sugar beet, whereas growers in western states had lower production costs with this technology.
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Document Type: Research Article
Publication date: 01 February 2010
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