Glyphosate -resistant Palmer amaranth in the Southeast

1. Glyphosate-resistant Palmer amaranth in the Southeast Culpepper, York, Marshall

2. Distribution of Glyphosate-Resistant Palmer Amaranth Southeastern U.S. Macon County, Georgia 2004 ACY 2009

3. Distribution of Glyphosate-Resistant Palmer Amaranth Southeastern U.S. 26 counties confirmed; more being tested ACY 2009

4. Distribution of Glyphosate-Resistant Palmer Amaranth Southeastern U.S. 11 counties confirmed in 2005 (red) 11 counties unconfirmed ACY 2009

5. Distribution of Glyphosate-Resistant Palmer Amaranth Southeastern U.S. 11 counties confirmed through 2007; more being tested ACY 2009

6. Distribution of Glyphosate-Resistant Palmer Amaranth Southeastern U.S. 600,000 acres with GR Palmer amaranth in Southeast ACY 2009

7. Georgia County Extension Survey Determining the Impact of GR Palmer on Cotton Production • Survey sent to 20 counties during fall of 2008. • Results reported with counties broken in three levels (severe, light to moderate, none to light).

8. Glyphosate-resistant Palmer amaranth infestation levels in Georgia. Severe (>60% land infested) Light to moderate infestations (20 to 60% land infested) Light infestations (<20% land infested)

9. Georgia County Extension Survey • Survey sent to 20 counties during fall of 2008. • Results reported with counties broken in three levels (severe, light to moderate, none to light). • Results weighted by cotton acreage.

10. Georgia Counties with Severe GR Palmer amaranth Infestations. Severe

11. Impact of GR Palmer amaranth in Georgia counties with severe infestations.* 92 88 25 25 2.7 2.0 Acres (%) treated with yellow herbicide Acres (%) treated with additional residual herbicide Number of glyphosate applications *Average of Macon, Taylor, Sumpter, Schley, and Dooly counties

12. Impact of GR Palmer amaranth in Georgia counties with severe infestations.* 83 % acres 48 45 26 20 5 0 0 0 0 Strip-tillage Herbicide Incorp. Glufos. systems Cultivation Hand weeding *Average of Macon, Taylor, Sumpter, Schley, and Dooly counties

13. Why???? • Reducing conservation tillage? • Increasing tillage?

14. Lack of herbicide activation in dryland production?

15. May 2008 Rainfall Distribution in Tifton (CPES) 1.4” 0.33” Herbicide activated 0.02” Prostko 2009

16. Most Palmer amaranth emerges from top 2.5 cm

18. Palmer amaranth seedling density

19. No Deep Tillage Deep Turned Prowl H20 + Reflex PRE; WeatherMax + Dual Magnum POST; Direx + MSMA Layby

21. Glyphosate 3 lb ae + Pyrithiobac 0.25 lb (Palmer 3 inch at time of application) Cultivation No cultivation

22. Why???? • Reducing conservation tillage? • Increasing tillage? • Why so much hand weeding?

24. In-field pollen movement

25. Number of Seed Produced per PlantGlyphosate-Resistant Weeds in US 450 K 309 K 230 K 28 K 250 Giant ragweed Johnson-grass Horseweed Waterhemp Palmer amaranth Ragweed = Harrison et al. 2001; johnsongrass = Warwick and Black (1983); horseweed = Regehr and Bazzaz (1979); waterhemp = Nordby and Hartzler (2004); Palmer amaranth = Macrae et al (2009).

26. Why???? • Reducing conservation tillage? • Increasing tillage? • Why so much hand weeding? • Why switching to glufosinate based program?

27. Dryland Conservation Tillage Pendimethalin + fomesafen PRE Glyphosate + S-metolachlor POST Diuron + MSMA PD Pendimethalin + fomesafen PRE Glufosinate + S-metolachlor POST Diuron + MSMA PD

28. Georgia Cotton OVTs – 2008Plains and Tifton Dryland Production

29. Georgia Counties with Light to Moderate GR Palmer amaranth Infestations. Light to moderate infestations

30. Impact of GR Palmer amaranth in Georgia counties with light to moderate infestations.* 95 95 75 61 2.2 1.8 Acres (%) treated with yellow herbicide Acres (%) treated with additional residual herbicide Number of glyphosate applications *Average of Crisp, Lee, and Wilcox counties.

31. Impact of GR Palmer amaranth in Georgia counties with light to moderate infestations.* 45 45 35 % acres 25 5 0 0 0 Strip-tillage Glufosinatesystems Cultivation Hand weeding *Average of Crisp, Lee, and Wilcox counties.

32. Glyphosate-resistant Palmer amaranth infestation levels in Georgia. Lighter infestations

33. Impact of GR Palmer amaranth in Georgia counties with light to no infestations.* 60 37 % acres 30 22 2 12 0 1 Strip-tillage Glufosinatesystems Cultivation Hand weeding *Average of Randolf, Colquitt, Turner, Berrien, Cook, Pulaski, Seminole.

35. Impact of GR Palmer amaranth in Georgia counties with light to no infestations.* 91 71 70 35 2.3 1.7 Acres (%) treated with yellow herbicide Acres (%) treated with additional residual herbicide Number of glyphosate applications *Average of Randolf, Colquitt, Turner, Berrien, Cook, Pulaski, Seminole.

36. Glyphosate-Resistant Palmer amaranth 2008 2006

37. Herbicide Expenses per Acre.* 52 $ 33 *Average of 10 counties responding. Does not included cultivation and hand weeding expenses.

38. Prevention and Early Detection are Essential!!!!

39. What’s replacing the glyphosate applications? • Averaged over all counties, glyphosate applications were reduced from 2.4 to 1.8 applications in crop. • Some glufosinate in severely infested fields. • Primarily conventional mixtures at layby including MSMA?

40. Percent Acres Treated with MSMA. Georgia Cotton 2008* 34 16 15 15 11 9 *N = 90 (70% grower, 15% Extension, and 15% consultant).

41. Impact of GR Palmer on North Carolina and South Carolina NC SC % Change in Conserv. Tillage: 0 -5 % Glufosinate Systems: 1 5 % Cultivation: 3 5 % Hand weeding: 17 50 % A treated w/Yellow: 40 75 % A treated with add. Herb: 40 55

42. Questions or Comments?