Submitted to: Proceedings Washington State Potato Conference
Publication Type: Proceedings
Publication Acceptance Date: March 29, 2009
Publication Date: July 17, 2009
Citation: Boydston, R.A. 2009. Managing Herbicide Drift and Early Results of Simulated Glyphosate Drift to Potato Study. Proc. 48th Washington State Potato Conference 1-4. 2009. Technical Abstract: The off target movement of herbicides can injure sensitive crops. Off target movement of spray droplets results from displacement by wind, poor application techniques, or improper settings or operation of application equipment. Applicators should be aware of wind speed and direction, use nozzles and sprayer operating pressures that result in larger spray droplets, keep sprayer boom height to a minimum, know what is in the spray tank, and be aware of neighboring sensitive crops. A summary of typical herbicide drift injury symptoms on potato from commonly used herbicides is presented. Glyphosate drift to sensitive crops is more likely to occur with increased use of glyphosate. In 2008, a simulated glyphosate drift study was conducted on Ranger russet potato Glyphosate was applied May 9, at 4 inch stage of potato; May 18, 6-8 inch tall potato (stolons swelling, early tuber initiation); May 27, 10 to 15 inches tall, (tuber initiation to 0.5 inch diameter tubers); and June 13 at row closure (tuber bulking). Glyphosate was applied at 0, 0.0075, 0.048, 0.09, 0.19, and 0.375 lb ae/a in a spray volume of 20 gpa. Potatoes treated with glyphosate exhibited chlorosis of the newest leaves at the higher rates of glyphosate tested and few or no symptoms at the lower rates of glyphosate tested. Foliar injury at 3 WAT was greater than at 1 WAT. Potato foliage recovered from most glyphosate applications and grew normally for the remainder of the season except for the higher rates of glyphosate tested. Injury to potato foliage was greatest from May 18 and May 27 glyphosate applications and least with May 9 applications to 4 inch potato. Glyphosate rates of 0.0075 lb ae/a caused very minor or no visual injury and had little or no effect on tuber yield or quality. Potato tuber yield was reduced most by glyphosate applications on May 18, whereas tuber quality was reduced most by glyphosate application on May 27. Tubers produced from potato plants treated with glyphosate in May had a high percentage of growth cracks, folds, and small sized tubers. Glyphosate applied at potato row closure in June tended to cause more scaly skin lesions on tubers and growth cracks on tuber ends.