Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 7, 2000
Publication Date: N/A
Interpretive Summary: Increasing acreages of no-till cropland and Roundup-resistant crops are sprayed with Roundup to control weeds. A considerable amount of these spray applications are made by aircraft. The manufacturer of Roundup as recently made an improvement in the formulation called Roundup Ultra. The first use of the improved formulation coincided with a major increase in acreage sprayed. There was also considerable increase in spray drift complaints and damage from the applications. Many aerial applicators thought the new formulation was the cause of increased incidents of spray drift. These concerns prompted an extensive field drift study and associated laboratory studies that were conducted to determine if the different formulations had different spray drift properties. These studies demonstrated that there were no meaningful differences in spray deposition, spray drift, and atomization in a wind tunnel between the formulations of Roundup and Roundup Ultra.
Technical Abstract: Glyphosate and similar herbicides have facilitated low and no-till production systems through more effective management of winter weeds before planting spring-seeded crops. Crop cultivars tolerant to specific herbicides are also more readily available. Increased use of these systems and their requirements for timely herbicide applications have increased the acreage of herbicides applied by aircraft. Manufacturers of glyphosate have also made some changes in the product formulations in an effort to provide improved efficacy and convenience. A combination of these and other factors have increased the incidence and raised awareness of spray drift from aerial applications of glyphosate. This study was conducted to provide information in response to those concerns. Four spray mixes of glyphosate from three different formulations were included in an extensive field study to determine relative drift propensity of the spray mixes from the different formulations. There were no meaningful differences in spray deposition, spray drift, and atomization in a wind tunnel between the glyphosate formulations of Roundup and Roundup Ultra.