Variety selection is the first and perhaps the most important management decision a grower makes each season. Variety decisions are now more complex due to the fact that numerous new varieties have been introduced to the market by seed companies during the last few years. There are many factors that govern the choice of cotton varieties, and one major factor or trait that growers must now consider when choosing varieties is the addition of value-added transgenic traits. The number of cultivars offered by seed companies containing value-added transgenic traits (Bollgard, Liberty-Link, Roundup-Ready, Roundup-Ready Flex, Bollgard II, Widestrike) for herbicide and insect resistance and the resulting planted acreage (approximately 98 % of acreage in 2006) has increased dramatically in South Carolina. The value of transgenic traits is an extremely important consideration for growers when selecting varieties; however, the value-added traits are not the most important traits to consider. Yield potential has always been the most important factor to consider in the selection of a good variety and is still the number one factor today. Without good genetics and high yield potential, any benefits obtained from the value-added transgenic traits are negated.

Roundup Ready technology has greatly improved our growers' success in controlling problem weeds, especially during the first four to six weeks after planting. Limitations of the Roundup Ready technology include label restrictions of topical applications beyond the 4-leaf stage and the lack of residual activity. Monsanto has developed Roundup Ready Flex technology, which allows topical applications of glyphosate up to 14 days before harvest. This technology was commercially available for the 2006 growing season. Growers are expected to rapidly adopt this technology over the next several growing seasons. This paper presents field performance information of Roundup-Ready Flex cotton varieties in the Southeast.