Weed management: transgenics and new technologies - a weed scientist's perspective

The development of transgenic cotton varieties resistant to Buctril and to Roundup Ultra, and the development of Staple herbicide has provided growers with opportunities to improve weed control, reduce reliance on preemergence herbicides, and reduce costs. In the irrigated cotton production regions of the West, these new herbicide technologies combined with precision guidance systems for cultivation and herbicide applications are being used to develop new strategies for cotton weed control. The most significant benefit of the new herbicide technologies is improved weed control without early season crop injury. These technologies provide a new window for herbicide applications, specifically over-the-top and post-directed applications from the cotyledon up to the 6 to 8 inch tall growth stage of cotton. Postemergence chemical weed control during this period reduces or eliminates early season weed competition which in turn increases yield and earliness. The absence of crop injury during early season cotton growth also increases yield and earliness. The new herbicide technologies have the potential to reduce crop injury in two ways. Buctril, Roundup Ultra, and Staple herbicide applications on small cotton replace postemergence applications of other less selective, injury causing herbicides such as MSMA (and other organic arsenicals), Caporal (prometryn), Cotoran (fluometuron), and Karmex (diuron). In addition, in some situations the use of Buctril, Roundup Ultra, and Staple may allow reduced use of preemergence herbicides (e.g. Caparol, Cotoran and Zorial) which can cause crop injury under adverse weather conditions.