Effect of Simulated Glyphosate Drift to Four Potato Processing Cultivars

Field research was conducted at the Northern Plains Potato Grower’s Association irrigated research site near Inkster, North Dakota, in 2012 and repeated in the same location in 2013 to evaluate the effects of simulated glyphosate drift in the current season and the effects of planting back the daughter tubers grown in the 2012 season. Treatments were applied at tuber initiation (TI), early tuber bulking (EB) and late tuber bulking (LB) stages to four potato processing cultivars: Russet Burbank, Umatilla, Ranger Russet and Bannock. During the current season glyphosate was applied at rates one-quarter, one-eighth, and one-sixteenth the lowest labeled rate in 2012, of 0.47 lb/A and respectively the standard use rate in 2013, of .95 lb/A during the TI and EB stages. During the LB stage of 2012, glyphosate was applied at the one-quarter, one-eighth, and one-sixteenth the standard use rate of 0.95 lb/A. Ammonium sulfate was tank mixed at a rate of 4 lbs/100 gal. The treatments were applied using a CO2-pressurized ATV sprayer with a spray boom extended to cover treated rows.  The sprayer output was 20 GPA at 40 psi using 8002 flat fan nozzles. Both years produced data that supported the Bannock variety to be the most sensitive cultivar at TI regardless of the sub-lethal rate applied. Ranger Russet appeared to be the least sensitive to the glyphosate treatments, however the variety did show a reduced marketable yield compared to the untreated when sub-lethal rates of 0.19 and 0.095 lb/A were applied at TI. Umatilla was considered a cultivar with intermediate sensitivity to glyphosate. Russet Burbank was also considered a cultivar with intermediate sensitivity to glyphosate, however the variety did show a reduced marketable yield compared to the untreated when sub-lethal rates of 0.19 and 0.095 lb/A were applied at TI. All four varieties when treated with sub-lethal rates at the EB and LB growth stages did not show a reduction in marketable tuber yield or tuber number compared to the untreated. The number of tubers increased with Russet Burbank, Umatilla, Ranger Russet, and Bannock when treated at TI with 0.095, 0.048, 0.19, 0.095 lb/A respectively. The plant back of daughter tubers from 2012 showed the Ranger Russet variety to be the least affected. Russet Burbank had the second highest total and marketable yields. Bannock or Umatilla seed from mother plants sprayed with sub-lethal glyphosate rates had the lowest total and marketable yields.