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The Perfect Storm? Why an invasive weed (Commelina benghelensis) threatens agriculture in the Southeast US

AUTHOR
Theodore M. Webster
Crop Protection and Management Research Unit
USDA-ARS
Tifton, GA

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TABLE OF CONTENTS
  1. The Perfect Storm? Why an invasive weed (Commelina benghelensis) threatens agriculture in the Southeast US
  2. Georgia Agriculture
  3. Cotton acreage as a % of total summer crop acreage
  4. The Perfect Storm? Georgia Agriculture: early 1990's
  5. The Perfect Storm? Georgia Agriculture: current situation
  6. Tropical spiderwort in cotton: After 2 Applications of Roundup
  7. Tropical spiderwort in peanut
  8. Tropical spiderwort Timeline
  9. Tropical spiderwort Distribution in Georgia
  10. Identification
  11. Of the 170 Commelina spp., it is one of a few that is vegetatively distinct
  12. Tropical spiderwort vs. Spreading dayflower Characteristics
  13. Red hairs at the apex of the membranous sheath
  14. Field conditions: 240 Aerial flowers/plant
  15. Of the nearly 250,000 species of flowering plants, 36 have underground flowers
  16. Field conditions: 19 Subterranean flowers/plant
  17. Four Types of Seeds!
  18. Tropical spiderwort growth
  19. Rapid growth between 48 and 69 DAP
  20. Between 40 and 69 DAP: 2.5 New Spathes Every Day
  21. Emergence Patterns
  22. Can we predict tropical spiderwort emergence?
  23. Growing degree days vs. Cumulative emergence
  24. Can We Control Tropical Spiderwort?
  25. Ability to Resist Control Tactics
  26. Ability to Resist Control Tactics
  27. Node pieces
  28. Can I minimize my cotton yield loss?
  29. How long can cotton tolerate the presence of tropical spiderwort before yield is affected?
  30. Weed free intervals maintained through hand-hoeing
  31. Spiderwort interference reduced cotton canopy growth
  32. Spiderwort interference reduced cotton canopy growth
  33. Yield Data
  34. Growing degree days vs. Cotton yield
  35. Growing degree days vs. Cotton yield
  36. Growing degree days vs. Cotton yield
  37. Growing degree days vs. Cotton yield
  38. Growing degree days vs. Cotton yield
  39. Growing degree days vs. Cotton yield
  40. Growing degree days vs. Cotton yield
  41. Critical Period of Spiderwort Control in Cotton
  42. Critical Period of Spiderwort Contro in Peanut
  43. Continuous Spiderwort competition with peanut, 6 WAP
  44. Weed-free peanuts vs. Weedy peanuts
  45. What other factors have contributed to the rapid explosion of Tropical Spiderwort in Georgia?
  46. The Amazing Rate of Spread?
  47. Cotton Gin Trash
  48. We're probably moving it around with cotton lint
  49. The secret to it's success?
  50. Corn is too tall for control tactics as Commelina benghalensis begins to germinate
  51. Lack of management in corn: Spiderwort can complete a generation in 42 days
  52. No post-crop harvest management
  53. Tropical spiderwort in this box for 3 months...
  54. Ability to vegetatively persist under unusual circumstances
  55. Future Research Directions
  56. Acknowledgements



SLIDE CONTENTS
  1. The Perfect Storm? Why an invasive weed (Commelina benghelensis) threatens agriculture in the Southeast US Theodore M. Webster Crop Protection and Management Research Unit USDA-ARS, Tifton, GA
  2. Georgia Agriculture 1988 Corn: 600,000 ac Cotton: 350,000 ac Soybean: 930,000 ac Peanut: 690,000 ac Wheat: 575,000 ac Total: 4,268,000 ac 2003 Corn: 340,000 ac Cotton: 1,450,000 ac Soybean: 190,000 ac Peanut: 540,000 ac Wheat: 380,000 ac Total: 3,807,000 ac
  3. Cotton acreage as a % of total summer crop acreage Boll weevil eradication Glyphosate-tolerant cultivars ~90%
  4. The Perfect Storm? Georgia Agriculture: early 1990’s Reliance on PRE Herbicides with soil residual activity (fluometuron: 90% acres) Only POST graminicides Cultivation: 2 to 3 cultivations/season Conservation tillage: <1% of cotton acres
  5. The Perfect Storm? Georgia Agriculture: current situation Reliance Roundup Ready Cotton Cultivars (90%) Abandonment of PRE Herbicides with soil residual activity (fluometuron: <10% acres) Cultivation: <15% acres Reduced tillage on 45% of the acres
  6. Grady County, GA Photo by Stanley Culpepper, UGA Tropical spiderwort in cotton After 2 Applications of Roundup Roundup: <55% control of tropical spiderwort 2- to 4 glyphosate applications/seasons may be the only herbicide applied
  7. Grady County, GA Tropical spiderwort in peanut s-Metolachlor - Rainfall, Cost Imazapic - Rotation Restrictions 2,4-D - Cotton proximity
  8. Native to Asia and Africa 1928: Introduced to US Mid-1930’s: Common throughout Florida 1983: Federally Noxious Weed 1998: not considered a serious pest in Georgia 2001: considered the 9th most troublesome weed in cotton 2002: Most troublesome weed facing cotton growers TROPICAL SPIDERWORT Commelina benghalensis
  9. Tropical Spiderwort Distribution in Georgia: Survey: Culpepper, UGA Weed Science Survey: Georgia Department of Agriculture 1999 Present in 5 Counties 2004 Present in 29 Counties
  10. Identification
  11. Alan York, NCSU Of the 170 Commelina spp., it is one of a few that is vegetatively distinct (Faden 1992)
  12. TROPICAL SPIDERWORT Tip more blunted Length:Width Ratio <3:1 SPREADING DAYFLOWER Tip sharper L:W Ratio >3:1 Mike Burton, NCSU 4.3 1.0 1.5 1.0
  13. Red Hairs at the apex of the membranous sheath Commelina virginica may also have red or white hairs, but it has narrow, long leaf blades (4:1 or greater)
  14. Aerial flowers begin forming 8 to 10 Weeks after emergence Field conditions: 240 Aerial flowers/plant (Kaul et al. 2002)
  15. Of the nearly 250,000 species of flowering plants… … 36 have underground flowers
  16. Underground flowers (within spathes) 2002 Arlene Mendoza North Carolina State University Subterranean flowers begin to form by 6 weeks after emergence Field conditions: 19 Subterranean flowers/plant (Kaul et al. 2002) It’s the only Commelina spp. in the U.S. to have spathes on rhizomes
  17. Four Types of Seeds!
  18. Tropical Spiderwort Growth
  19. Between 48 and 69 DAP: Number of Shoots More Than Doubled Transplanted 5-Leaf Tropical Spiderwort at Day=0; Greenhouse Study RAPID GROWTH
  20. Between 40 and 69 DAP: 2.5 New Spathes Every Day Transplanted 5-Leaf Tropical Spiderwort at Day=0; Greenhouse Study Seeds Viable within 25 days of flowering (?) 1 to 3 Flowers/Spathe Usually 3 seeds/Aerial Flower Maheswari and Maheshwari 1955
  21. Emergence Patterns
  22. Can we predict tropical spiderwort emergence?
  23. 20% 65% June 17 May 28 29% 82% June 24 May 28 27% 46% July 13 June 15 25% 84% August 3 July 7 170 GDD 374 GDD 378 GDD 220 GDD 386 GDD 182 GDD 166 GDD 390 GDD
  24. Grady County, Georgia Can We Control Tropical Spiderwort?
  25. Tropical Spiderwort: Hoed 1 week ago ABILITY TO RESIST CONTROL TACTICS Does cultivation control spiderwort or sprig it?
  27. Mike Burton, NCSU 3 Weeks After Planting 3 Node Pieces Buried: 2.5, 5, 7.5, 10 cm 3 Node Pieces: Sprigged, 1 Node Above Ground
  28. Hoeing weather… Can I minimize my cotton yield loss? Hypothesis Cotton planting date will affect the impact of spiderwort on cotton yield Early-planted cotton will be more competitive with spiderwort than late-planted cotton
  29. How long can cotton tolerate the presence of tropical spiderwort before yield is affected? WEEDY Duration - Spiderwort competed for: 2 Wks 4 Wks 6 Wks 8 Wks 10 Wks WEED-FREE Duration – Plots Free of Spiderwort for: 2 Wks 4 Wks 6 Wks 8 Wks 10 Wks Cotton Planted: 30 April 2003 (DP 555 BG/RR) 18 May 2004* (DP 555 BG/RR) 13 June 2004 (DP 424 BGII/RR) Pendimethalin applied PRE Center-pivot irrigation as needed Naturalized population of spiderwort
  30. 960 Worker-Hours in 2004 Weed-free intervals maintained through hand-hoeing
  31. Weed-Free All Season 6 Wks Weedy, then Weed-Free 8 Wks Weedy, then Weed-Free 10 Wks Weedy, then Weed-Free 22 July 2003 Spiderwort interference reduced cotton canopy growth
  32. 22 July 2003 Weedy All Season 2 Wks Weed-Free Then Weedy 4 Wks Weed-Free, then Weedy 6 Wks Weed-Free, then Weedy
  33. Yield Data
  34. Field Study, Grady County, Georgia; Cotton Planted April 30, 2003 WF All Season 2 WY Then WF 4 WY Then WF 6 WY Then WF 8 WY Then WF: 45% 10 WY Then WF WY All Season
  35. Field Study, Grady County, Georgia; Cotton Planted April 30, 2003 WY All Season 2 WF Then WY 4 WF Then WY 8 WF Then WY 10 WF Then WY WF All Season 6 WF Then WY: <10%
  36. Field Study, Grady County, Georgia; Cotton Planted April 30, 2003 95% Yield
  37. Field Study, Grady County, Georgia; Cotton Planted May 18, 2004 <20%
  38. Field Study, Grady County, Georgia; Cotton Planted May 18, 2004 A single weed control event initiated between 225 to 238 GDD, Just prior to 6 WAP
  39. Field Study, Grady County, Georgia; Cotton Planted June 13, 2004 ~45%
  40. Field Study, Grady County, Georgia; Cotton Planted June 13, 2004
  41. Critical Period of Spiderwort Control April ‘03: 200 to 350 GDU May ‘04: 225 to 238 GDU June ’04: 85 to 454 GDU
  42. Continuous spiderwort competition with peanut, 2 WAP Critical Period of Spiderwort Control in Peanut
  43. Continuous spiderwort competition with peanut, 6 WAP Effective weed control 4 Weeks Later
  44. Weed-free Peanuts Weedy Peanuts No peanuts to harvest
  45. What Other Factors Have Contributed To The Rapid Explosion of Tropical Spiderwort in Georgia?
  46. County Maintained Road Adjacent to Test Site Grady County, Georgia How’s it spreading so fast? How long has it been here? Are we just selecting for it with our current management programs? 1. It’s probably been around for a while The Amazing Rate of Spread?
  47. Cotton Gin Trash
  48. 2. We’re probably moving it around with cotton lint
  49. The secret to it’s success? Corn planted in March
  50. Corn is too tall for control tactics as Commelina benghalensis begins to germinate Atrazine has dissipated prior to June
  51. Tropical spiderwort: August 3. Lack of management in corn; Spiderwort can complete a “generation” in 42 days
  52. Tropical Spiderwort: September 4. No post-crop harvest management
  53. Tropical spiderwort In this box For 3 months…
  54. … 10 days after putting this into water 5. Ability to vegetatively persist under unusual circumstances
  55. Future Research Directions Develop an accurate predictive model for tropical spiderwort germination Evaluate the seedbank longevity of tropical spiderwort Determine the primary dispersal mechanism(s) Characterize the environmental limits of tropical spiderwort in the US
  56. Acknowledgements: Thomas E. Sklany (Study Coordinator) James Davis (Study Coordinator) Amy Davis Steven Fulghum Stefanie Cross Van Jones Darryl Bryner Charlie Hilton Carroll Johnson Robert Giddens Chad Burkhalter Jacob Feyereisen Jessica Daniel Amanda Webb Michael Smith Grower Cooperators: Mark and Elden Whigham Donald Connell Jim Tenewitz Supported by: Georgia Cotton Commission Cotton Incorporated Georgia Cotton Farmers