Weed Control in Arizona Ultra Narrow Row Cotton: 1999 Preliminary Results

Abstract

In two 1999 Arizona studies, a preplant incorporated (PPI) application of Prowl (2.4 pt/A) or Treflan (0.75 lb a.i./A) followed by a topical Roundup Ultra (1 qt/A) application at the 3 to 4 true leaf cotton growth stage provided good weed control. At the University of Arizona Maricopa Agricultural Center field that had low density weed populations, a postemergence topical Staple (1.8 oz/A) application also provided good weed control was more expensive. At the Buckeye, Arizona study site, a PPI application of Prowl at a reduced rate (1.2 pt/A) was as effective as the full rate (2.4 pt/A) but a preemergence application of Prowl (2.4 pt/A) was not as effective as either of the PPI Prowl rates or PPI Treflan (0.75 lb a.i./A). A postemergence topical Staple application (1.8 oz/A) following the Roundup Ultra application did not significantly improve weed control. After one field season of experimentation and observation in Arizona UNR cotton, experience suggests that in fields with low to moderate weed populations, a PPI Prowl or Treflan application followed by a postemergence topical Roundup Ultra application will provide acceptable weed control in most fields. However, the presence of nutsedge or other difficult to control weeds may require two postemergence topical Roundup Ultra application prior to the four leaf growth stage of cotton. More research is needed to further explore weed control options in Arizona UNR cotton production systems.