2009 Weed Management in Cotton

1. 2009 Weed Management in Cotton

2. Getting Serious About Herbicide-Resistant Weeds

3. Managing Herbicide Resistance • Attitudes and acceptance • Resistance is real • It can happen on any farm; • It can happen with any herbicide; resistance is not unique to glyphosate • Far better to prevent it, but learn to deal with it if you already have it

4. Herbicide Resistance in US by Mode of Action Nitriles Carotenoid biosyn. inhibitors PPO inhibitors Bipyridiliums Thiocarbamates Arsenicals Auxins Ureas DNA’s Glycines ACCase inhibitors PS II inhibitors (triazines) ALS inhibitors ACY 2008

6. Glyphosate-Resistant Horseweed • Identified in 16 states • Initially found in NC in 2003 • Slow increase during 2003-2007; less than expected • Exploded in eastern NC in 2008

7. Glyphosate-Resistant Horseweed • Resistant biotype likely will be more prevalent in 2009 • Wind-borne seed; easily moves long distances • East of US 1, assume it is glyphosate- resistant and act accordingly; implement appropriate burndown program Photo by R. Hayes

8. Burndown Programs for Glyphosate-Resistant Horseweed in Cotton, Corn, Full-season Soybean First choice: Roundup + Clarity (1/2 pt)* + residual herbicide

9. Time of horseweed emergence in west Tennessee. Adapted from Main et al., 2006. Jackson 2002-03 Milan 2002-03

10. Burndown Programs for Glyphosate-Resistant Horseweed in Cotton, Corn, Full-season Soybean First choice: Roundup + Clarity (1/2 pt)* + residual herbicide ____________________________________________ * Waiting intervals required; Apply mid-February to early March

12. Waiting Period after Clarity Preplant Application Corn: no waiting period Soybean: 14 days (for 8 oz rate) Cotton: Following accumulation of 1 inch rainfall, wait 21 days

13. Burndown Programs for Glyphosate-Resistant Horseweed in Cotton, Corn, Full-season Soybean First choice: Roundup + Clarity (1/2 pt)* + residual herbicide Second choice: Roundup + 2,4-D (1.5-2 pt)* + residual herbicide ____________________________________________ * Waiting intervals required; Apply mid-February to early March

14. Waiting Period after 2,4-D Preplant Application* Cotton Crops listed as use sites on this or other registered 2,4-D labels may be planted within 29 days of application. All other crops (cotton included here) may be planted 30 or more days following application without concern for illegal residues in the planted crop. However, under certain conditions, there may be a risk of injury to susceptible crops. Degradation factors should be considered in weighing this risk. Less risk if conditions following application include warm, moist soils. Under normal conditions, any crop may be planted without risk of injury if at least 90 days of soil temperatures above freezing haveelapsed since application. * Includes some brands of both amine and ester formulations.

15. Untreated Roundup only Roundup + Valor Edgecombe Co., NC 2008 8 weeks after burndown Roundup + Valor + Clarity Roundup + Valor + 2,4-D

16. Untreated Roundup only Roundup + Valor Edgecombe Co., NC 2008 12 weeks after burndown (and after two in-crop applications Roundup, except check) Roundup + Valor + Clarity Roundup + Valor + 2,4-D

17. Burndown Programs for Glyphosate-Resistant Horseweed in Cotton, Corn, Full-season Soybean First and second choices: Roundup + Clarity (1/2 pt)* + residual herbicide Roundup + 2,4-D (1.5-2 pt)* + residual herbicide Third choice: Ignite (29 oz), temperature > 75F, at or near planting, plus a residual Fourth choice: Gramoxone + PS II inhibitor (atrazine, Direx, Canopy, Linex) (may not be adequate) ____________________________________________ * Waiting intervals required

18. In-Crop Control of Glyphosate-Resistant Horseweed Cotton: Ignite under hood (any variety) Ignite overtop LL variety Ignite requires GOOD coverage

19. Ignite hooded on horseweed (not LL cotton) Oops!

21. Managing Glyphosate-Resistant Palmer Amaranth • Can’t ignore it and hope it goes away; it is not going away • Prolific seed production • 450,000 seed/plant grown in competition with • cotton (Sosnoskie and Culpepper, UGA)

23. Managing Glyphosate-Resistant Palmer Amaranth • Can’t ignore it and hope it goes away; it is not going away • Prolific seed production • Continued selection; can manage this • Spread of resistance • Seed movement; equipment, gin trash • Pollen-mediated gene flow Pollen from resistant male can fertilize susceptible female at least 1,000 ft away; resistant offspring (Sosnoskie and Culpepper, UGA)

24. Managing Glyphosate-Resistant Palmer Amaranth • Considerations in developing a management strategy • Prevention is the goal; reduce seed bank

25. Managing Glyphosate-Resistant Palmer Amaranth • Considerations in developing a management strategy • Prevention is the goal; reduce seed bank • No POST salvage options in cotton • What is the implication?

26. Managing Glyphosate-Resistant Palmer Amaranth • Considerations in developing a management strategy • Prevention is the goal • No POST salvage options in cotton • ALS resistance (Staple, Envoke, others) is wide-spread; multiple resistance

27. Weathermax 88 oz Staple LX 10 oz

28. Managing Glyphosate-Resistant Palmer Amaranth • Considerations in developing a management strategy • Prevention is the goal • No POST salvage options in cotton • ALS resistance (Staple, Envoke, others) is wide-spread; multiple resistance • Increasingly concerned over potential for resistance to PPO inhibitors

29. PPO inhibitors for the Southeast

31. Impacts of Roundup Ready Technology On Cotton Weed Management • Reduced or eliminated use of other herbicides • Allowed successful transition to no-till • Eliminated cultivation

32. Impacts of Roundup Ready Technology On Cotton Weed Management • Reduced or eliminated use of other herbicides • Allowed successful transition to no-till • Eliminated cultivation • Unprecedented selection pressure for • glyphosate-resistant biotypes

33. Herbicide Resistance Management (avoidance) • The focus must be on • reducing selection pressure.

34. Glyphosate Resistance Management (reducing selection pressure) • Minimize the seed bank • Do not depend entirely on glyphosate • Incorporate other modes of action, specifically residuals, into the program; most effective to do that on the front end • Use full rates • Start clean, stay clean • Take advantage of non-chemical control where practical; • cultivation or cover crops • 6. Vigilance! Watch for escapes, do not let them seed out

35. Is this weed resistant? Want to risk it? ACY2008

36. GR Palmer Amaranth Management in Cotton • Southeast Recommendations • Herbicide program: • Aggressive preplant/preemergence program.

37. Palmer amaranth control by PRE herbicides; 40 days* Reflex Staple (susceptible) Direx Cotoran Prowl Caparol % control * Average of 5 locations; 2 in GA, 3 in NC. Very heavy infestations. No other herbicides included.

38. PRE herbicides in Palmer amaranth management system. Four locations, NC.* No PRE Prowl Direx Reflex Staple Prowl + Reflex Reflex + Direx Reflex + Staple Direx + Staple * All with glyphosate/s-metolachlor POST-1, glyphosate POST-2, conventional layby.

39. Palmer amaranth control by PRE herbicides; 40 days* Valor Reflex Staple (susceptible) Direx Cotoran Prowl Caparol % control * Average of 5 locations; 2 in GA, 3 in NC. No other herbicides included.

40. Strip-Till After Valor Preplant

41. Waiting Intervals for Valor Preplant in Cotton 2 oz/acre

42. GR Palmer Amaranth Management • Southeast Recommendations • Herbicide program: • Aggressive preplant/preemergence program. • Dual Magnum (or other metolachlor product) early POST; to extend residual control • Residual herbicide(s) lay-by • Limit PPO inhibitors to one application/year

43. Roundup + 2,4-D burndown Gram. + Reflex PRE Roundup + Dual first POST Roundup second POST Direx + MSMA Layby

45. Glyphosate-resistant Palmer amaranth, Wayne Co., NC 2008; PRE herbicide followed by Roundup tank mix

46. Most POST soybean herbicide labels specify 6-leaf or 4-inch maximum Palmer amaranth Harmony SG label specifies 8-inch maximum Palmer amaranth

47. ACY2008

49. Untreated Atrazine-based program

50. Herbicide Resistance • and Crop Insurance • Concern by insurance companies • Failure to follow good farming practices • is not an insurable loss • Keep records to document what you did, • and whose advice you followed