The Transition From BGRR to B2RF Varieties and Its Impact On Cotton Management in the Southeast: Research and Observations in 2009

Until recently, most cotton varieties in the Southeast have expressed BGRR technology allowing growers to apply glyphosate up to the 4-leaf stage, after which some mild fruit abortion may result.  These BGRR varieties will no longer be available after 2010.  The recent release of B2RF varieties has allowed growers to apply glyphosate at any growth stage while avoiding any fruit abortion due to glyphosate.  Some observed characteristics of B2RF varieties include improved fruit retention on lower nodes, resulting in more compact fruiting and thus earlier maturity.  These fruiting characteristics could potentially require less aggressive PGR rates or application strategies, and could also influence defoliation timing.  The objective of these experiments was to investigate the potential interactions of herbicide technology with PGR application strategies and rate, and defoliation timing, with regard to fruit distribution, maturity, and lint yield of cotton.  Results from this experiment could significantly impact cotton management in the southeast, especially in states like Georgia, where aggressive late-maturing BGRR varieties have recently comprised over 85 percent of the cotton acres.