By Fred Bourland and Bill Robertson
In recent years, the presence of glyphosate-resistant pigweed in Mid-South cotton has compelled producers to grow glufosinate (Liberty)-tolerant varieties. In 2015, more than 85 percent of cotton acreage in Arkansas was planted to varieties that are tolerant to glufosinate. This acreage included 11 percent planted to XtendFlex (resistant to dicamba) varieties.
However, dicamba applications beyond the current burndown label were not allowed. Almost half of the transgenic entries in the 2015 Arkansas Cotton Variety Test were resistant to dicamba or 2,4-D (Enlist) – a clear indication of the direction of variety development.
The Enlist trait is fully registered in the United States, and the herbicide is labeled in all Mid-South states except Tennessee. Registration is pending for use of Enlist Duo herbicide on cotton with the Enlist trait. Import approvals for some Far East countries are still being pursued. We expect a limited release of Enlist cotton in 2016. It is expected, but at this point still uncertain whether labels will allow spraying of dicamba beyond burndown on XtendFlex cotton in 2016. Thus, producers should make their variety choices accordingly and follow all label requirements.
Selection of varieties then returns to long-established principles of choosing varieties that are likely to produce stable, high yields of premium quality cotton – regardless of their transgene configuration. Producers should maintain a base of varieties that have previously performed well in their area, and then explore the use of alternative varieties on a limited basis.
Results from state variety tests and local strip tests/demonstrations should be used to determine which specific variety to plant. Parameters from these tests usually include lint yield and fiber quality. Additionally, our Arkansas Cotton Variety Test report (www.ArkansasVarietyTesting.com) includes measures of maturity, yield components (how yield is attained), pubescence (hairs on leaves, stems and bracts) and host plant resistance.
Low cotton prices are forcing producers to carefully consider every production input. Technology fees may be avoided if viable alternatives are available. To be viable, the alternative must provide cost-effective control of weeds and/or worms and produce competitive yield and acceptable fiber quality.