1. Kevin B. Kelley and Lloyd C. Haderlie AgraServ, Inc., American Falls, ID

2. Aminopyralid Auxinic herbicide labeled for use on rangeland, permanent grass pastures, CRP land, non-cropland areas, and natural areas. Very active on several annual and perennial broadleaf weeds, including Canada thistle. Known to pass through animals that consume treated forage and be present in manure and urine similar to picloram. Shorter soil half-life than picloram.

3. Aminopyralid Injury to Potatoes Research Prompted by Farmer Complaints Aerial applications of aminopyralid to range/pasture in 2008 Potatoes bordering pasture in 2008 and 2009 showed injury symptoms and yield loss Weeds sensitive to aminopyralid in potato fields didnt show injury Laboratory analysis of potato foliage and tubers resulted in positive detection of aminopyralid

6. Aminopyralid Affect on Potatoes Persistence in the soil? Potato sensitivity? Growth stage differences? Daughter tuber response?

7. Methods - Timing Fall Soil Carryover Applied Nov. 7, 2009 Spring Preplant Applied May 18, 2010 – One day before planting In Season Early – Applied 2 weeks after emergence Mid-Season – Applied late July near row closure Daughter Tuber Plant Response Applied Aug. 31, 2009 Treated tubers planted May 2010 Known to be a very sensitive assay for picloram

8. Methods - Rates Aminopyralid – Use rate range - 53 to 123 g ai/ha applied from 44 g ai/ha (~50%) down to 0.044 g ai/ha (0.05%) Picloram – Average use rate - 280 g ai/ha applied at 4.4 and 44 g ai/ha Clopyralid – Max use rate of 280 g ai/ha applied at 26 or 280 g ai/ha Dicamba – Average use rate of 560 g ai/ha applied at 56 or 560 g ai/ha

9. Fall Soil Carryover Potato Injury July 16th b b bc c LSD – 4 (P=0.1) Percent Injury Aminopyralid – g ai/ha

10. Fall Soil Carryover Total Potato Yield a LSD – 41 (P=0.1) Aminopyralid – g ai/ha a aaa CWT per Acre

11. Fall Soil Carryover US #1 Potato Yield LSD – 37 (P=0.1) Aminopyralid – g ai/ha CWT per Acre a a a a b

12. Spring Preplant Applied Potato Injury Aug 10th LSD – 17 (P=0.1) Rates in g ai/ha Aminopyralid Percent Injury a a b b b c cd d

13. Spring Preplant Applied Total Potato Yield LSD – 78 (P=0.1) Rates in g ai/ha Aminopyralid CWT per Acre a ab abcbc

14. In-Season Applied Potato Injury Aug 10 th (6 or 2 WAA) LSD – 6 (P=0.1) Rates in g ai/ha Aminopyralid Two Weeks After EmergenceNear Row Closure Percent Injury a b c f gg c de d g fg de e fg gg

15. In-Season Applied US #1 Potato Yield CWT per Acre LSD – 71 (P=0.1) Rates in g ai/ha Aminopyralid Two Weeks After EmergenceNear Row Closure hgh fg a-e b-e ab ef a-d cde abc def a a-e ef a-d

16. Daughter Tuber Plant Response - Potato Injury Aug 10, 2010 (Sprayed 2009) LSD – 9 (P=0.1) Aminopyralid – g ai/ha a b c cc Percent Injury

17. Daughter Tuber Plant Response – Total Potato Yield (Sprayed 2009) LSD – 67 (P=0.1) Aminopyralid – g ai/ha CWT per Acre a a a b c

22. Summary Aminopyralid injured potatoes and reduced yield and quality following all scenarios tested including fall applied to soil. Injury levels were similar to or exceeded that caused by picloram Greater rates of dicamba or clopyralid were required to cause potato injury. Potatoes appear to be especially sensitive to aminopyralid. All potatoes were saved for seed grow out in 2011.

23. Questions?