Changes in Cotton Weed Management Practices in Georgia following Glyphosate-Resistant Palmer Amaranth

1. 2012: Changes in Cotton Weed Management Practices in Georgia Following the Development of Glyphosate-Resistant Palmer Amaranth Lynn M. Sosnoskie1,2 and A. Stanley Culpepper1 1University of Georgia - Tifton 2University of California - Davis

2. Distribution of GR Palmer amaranth Map credit: R. L. Nichols

3. Cotton producing regions in US Map credit: http://www.cottonusa.org/

4. Glyphosate-resistant cotton:Changes in weed management Shaner (2000) Pest Manage. Sci. 56:320-326. Glyphosate use increasing in cotton Concomitant decrease in: PS II inhibitors – diuron, fluometuron, prometryn DNAs – pendimethalin, trifluralin Arsenates – MSMA Carotenoid biosynthesis inhibitors - clomazone

5. Glyphosate-resistant cotton:Changes in weed management Young (2006) Weed Technol. 20:301-307. Increase in glyphosate applications: 1/crop (1996) to 1.8/crop (2001) Decreased use of fluometuron and trifluralin: Fluometuron - 27-44% (1992-1998) to 20-27% (1999-2001) Trifluralin – 52-67% (1992-1999) to 30-39% (2000-2001) Glyphosate – 30-36% (1998-1999) to 56-57% (2000-2001)

6. Objective: To determine if cotton weed management practices in Georgia have changed following the development of glyphosate-resistant Palmer amaranth

7. Survey development and administration Two surveys (growers and extension agents) Surveys were designed by the authors and reviewed by an expert committee consisting of: extension agents, University (UGA and other) research scientists, UGA rural sociologist, industry personnel Surveys were ‘identical’ except for the fact that the growers were asked (anonymously) about their individual farming practices and agents provided 3rd party information about county-wide activities

8. Survey development and administration Final survey was 8 pages long, contained 19 questions, and was administered in person Survey sections: Commodities/acreage Herbicide use Additional weed management practices Tillage, cultivation, hand-weeding Weed problems Including the presence and severity of glyphosate-resistant Palmer amaranth BEFORE 2000-2005 AFTER 2006-2010

9. Survey development and administration E-mail was sent to all Georgia extension agents with cotton responsibilities (2010) describing the survey and requesting that they and 3-5 ‘representative’ growers in their county participate in the process Grower qualifications: Cotton production Responsible for making (agricultural) decisions on their property Did not work for a chemical manufacturer, distributor, of retailer, nor a seed company

10. County Data2009 Georgia Farm Gate Value Report (AR-10-01) * Extension agent from Colquitt County also returned a survey (54,010 acres, $42.1 Million, Rank = 2).

12. Total grower (n = 65) acres = 129,615 (12.6% of GA cotton) Total agent county (n = 10) acres = 246,034 (24% of GA cotton)

13. Commodities - example Grower Question 4: How many acres do you farm?____________________ Grower Question 5: What types of agricultural commodity groups do you produce on your farm? Yes No Approximate number of acres or number of heads, houses or ponds Row and forage crops ___ ___ _____________________ Poultry and eggs ___ ___ _____________________ Livestock and aquaculture ___ ___ _____________________ Forestry products ___ ___ _____________________ Vegetables ___ ___ _____________________ Ornamental horticulture ___ ___ _____________________ Other (Please describe) (Continued on next page)

14. Commodity composition of growers' farms

15. Herbicides - example Grower Question 9: What herbicides have you relied on for weed control in cotton before (2000-2005) and after (2006-2010) the development of glyphosate-resistant Palmer amaranth (pigweed)? On what percent of you row crop acreage have you used each product? PREPLANT and PREEMERGENCE (burndown (including early), applications made at or prior to planting, and applications made prior to cotton emergence): Before (2000-2005): After (2006-2010): Yes No Average % of Acres Yes No Average % of Acres Roundup, Glyphomax, Touchdown, others ___ ___ _________________ ___ ___ _________________ 2,4-D ___ ___ _________________ ___ ___ _________________ Aim ___ ___ _________________ ___ ___ _________________ Clarity ___ ___ _________________ ___ ___ _________________ Valor SX ___ ___ _________________ ___ ___ _________________ Direx, others ___ ___ _________________ ___ ___ _________________ Firestorm, Parazone, Gramoxone Inteon ___ ___ _________________ ___ ___ _________________ (Continued on next page)

16. Herbicides - example Herbicides are not divided up/grouped by MOA, activity, selectivity Grouped by timing of application as expressed in Georgia Pest Management handbook (http://www.ent.uga.edu/pmh/). 1. PREPLANT and PREEMERGENCE (burndown (including early), applications made at or prior to planting, and applications made prior to cotton emergence): 2. POSTEMERGENCE OVER-THE-TOP (following cotton emergence): 3. POSTEMERGENCE DIRECTED:

17. Growers: Pre-plant herbicides appliedPercent (%) of acres treated * * *

18. Agents: Pre-plant herbicides appliedPercent (%) of acres treated * * *

19. Growers: Pre-plant*/PRE herbicides appliedPercent (%) of acres treated * * * *

20. Agents: Pre-plant*/PRE herbicides applied Percent (%) of acres treated * * * *

21. PPI herbicides appliedPercent (%) of acres treated * GROWERS AGENTS

22. Growers: POST herbicides appliedPercent (%) of acres treated * * *

23. Agents: POST herbicides applied Percent (%) of acres treated * * *

24. Growers: PD herbicides applied Percent (%) of acres treated * * *

25. Agents: PD herbicides appliedPercent (%) of acres treated * * * * *

26. Growers: Changes in glyphosate and glufosinate applications from 2000-2005 to 2006-2010 *

27. Agents: Changes in glyphosate and glufosinate applications from 2000-2005 to 2006-2010 *

28. Growers 2000-2005: Herbicide costs = $32.30/A 2006-2010: Herbicide costs = $62.50/A

29. Agents 2000-2005: Herbicide costs = $27.80/A 2006-2010: Herbicide costs = $68.00/A

30. Additional practices - example Grower Question 13: Have you ever hand-weeded cotton due to insufficient chemical or mechanical weed control before (2000-2005) and after (2006-2010) the development of glyphosate-resistant Palmer amaranth (pigweed)? Before (2000-2005): After (2006-2010): Yes No Average % of Acres Yes No Average % of Acres ___ ___ ___________________ ___ ___ ___________________ Grower Question 14: Please estimate the cost of hand-weeding in cotton before (2000-2005) and after (2006-2010) the development of glyphosate-resistant Palmer amaranth (pigweed). Before (2000-2005): After (2006-2010): ____________________________$/Acre ___________________________$/Acre (Continued on next page)

31. 2000-2005: 17% of growers hand-weeded 5% cotton acres at $2.40/A 2006-2010: 92% of growers hand-weeded 52% cotton acres at $23.70/A Photo by A.C. York 2010

32. 2000-2005: According to agents, growers hand-weeded 3% cotton acres at $3.50/A 2006-2010: According to agents, growers hand-weeded 66% cotton acres at $21.70/A Photo by A.C. York 2010

33. Growers: Changes in tillage/planting practices from 2000-2005 to 2006-2010

34. Agents: Changes in tillage/planting practices from 2000-2005 to 2006-2010

35. In-row cultivation • Growers: 2000-2005: 34.3% of cotton acres cultivated 2006-2010: 43.9% of cotton acres cultivated • Agents: 2000-2005: 13.1% of cotton acres cultivated 2006-2010: 32.1% of cotton acres cultivated

36. Growers: Most troublesome weed* * Summed averages are greater than 100% because of multiple votes for most troublesome species/grower

37. Growers: 2nd Most troublesome weed* * Summed averages are greater than 100% because of multiple votes for most troublesome species/grower

38. Agents: Most troublesome weed

39. Agents: 2nd Most troublesome weed