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AUTHOR
Tim R. Murphy
The University of Georgia
Crop and Soil Sciences

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TABLE OF CONTENTS
  1. Turfgrass Herbicide Use Characteristics
  2. Preemergence herbicides are the foundation of annual grass control.
  3. Preemergence herbicides do not prevent weed seeds from germinating
  4. Preemergence Options
  5. The majority of herbicides used for preemergence annual grass control are dinitroanilines and dithiopyr
  6. Ronstar (oxadiazon)
  7. What is the best preemergence herbicide for turfgrass??
  8. It depends....
  9. Preemergence Herbicide Selection
  10. Preemergence Herbicide Selection
  11. Annual Grass Control Ratings
  12. Crabgrass spp.
  13. Crabgrass
  14. Goosegrass
  15. Goosegrass
  16. Goosegrass vs Crowfootgrass
  17. Goosegrass Cultural Controls
  18. Goosegrass Cultural Controls
  19. Core Aerification
  20. Annual bluegrass
  21. Quote from Callahan and McDonald
  22. Annual bluegrass control
  23. Preemergence Herbicides
  24. Preemergence Herbicides
  25. Relative Solubility of Preemergence Herbicides
  26. Preemergence Herbicide Volatility
  27. Irrigation Timing and Formulation Effect on Crabgrass Control with Pendimethalin
  28. Granular Formulations
  29. Fertilizer/Preemergence Products
  30. Fertilizer/Preemergence Products - Other Considerations
  31. Preemergence Herbicides - Formulation Effects
  32. Preemergence Herbicides - Formulation Effects
  33. Preemergence Herbicides- Formulation Effects
  34. Preemergence Herbicide Timing
  35. Suggested Application Dates
  36. Timing Summer Annual Grass Control
  37. Repeat Applications - Summer
  38. Guidelines - Preemergence
  39. Lack of Preemergence Herbicide Performance
  40. Broadleaf Control
  41. Growth Regulator Herbicides
  42. Broadleaf Herbicides
  43. Phenoxy + Dicamba Herbicides
  44. Phenoxy + Dicamba Herbicides
  45. Phenoxy, Dicamba, Picolinic Herbicides
  46. Post Herbicide Use Guidelines
  47. Post Herbicide Use Guidelines
  48. Post Herbicide Use Guidelines
  49. Examples of Rain-Free Periods
  50. Post Herbicide Use Guidelines
  51. Post Herbicide Use Guidelines
  52. Non-Target Plants
  53. Nonselective Broadleaf Control
  54. Lack of Post Herbicide Performance
  55. Lack of Post Herbicide Performance



SLIDE CONTENTS
  1. Turfgrass Herbicide Use Characteristics Tim R. Murphy The University of Georgia
  2. Preemergence herbicides are the foundation of annual grass control.
  3. Turfgrass roots below the herbicide layer Herbicide layer Weed seeds germinate and are controlled as they come in contact with the herbicide. Preemergence herbicides do not prevent weed seeds from germinating.
  4. Preemergence Options
  5. The majority of herbicides used for preemergence annual grass control are dinitroanilines and dithiopyr DNA’s Barricade Pendulum Surflan Balan Treflan Dimension Best used on established turf. Mitotic inhibitors. Immobile in the soil
  6. Ronstar (oxadiazon) Not a mitotic inhibitor Preferred herbicide for sprigging or high traffic areas (athletic fields, tees, etc.) Preferred herbicide for preemergence goosegrass control Will control crabgrass but is more effective on goosegrass
  7. What is the best preemergence herbicide for turfgrasses??
  8. It depends……….
  9. Preemergence Herbicide Selection Turfgrass species Weed species Immature vs. established Time of year Irrigation capabilities Renovation plans
  10. Preemergence Herbicide Selection Granular or spray equipment Desired control level Application frequency Ornamental tolerance Cost??
  11. Annual Grass Control Ratings
  12. Crabgrass spp. Summer annual At least 5 species in GA (tropical, smooth, large, southern, blanket) Germinates at soil temps. - 53 to 58 F., 4 inch depth Light required
  13. Southern crabgrass Smooth crabgrass
  14. Goosegrass Summer annual Germinates - soil temp. 4 inch depth averages 60 to 65 F. Usually germinates 2 to 6 weeks later than crabgrass Light required
  15. goosegrass Summer annual Prefers compacted areas that are overwatered
  16. goosegrass crowfootgrass
  17. Goosegrass Cultural Controls Aerify to alleviate compaction Redirect traffic Control watering Encourage dense turf
  18. Core Aerification Previously thought to break up herbicide layer and reduce weed control Research shows little increased crabgrass or goosegrass due to core aerification
  19. Annual bluegrass Winter annual Germinates late summer-fall at soil temperatures around 70 F. Second germination flush in mid- to late-winter
  20. Continuous annual bluegrass seed germination occurred from mid-Nov. through early January in Knoxville, TN. Callahan and McDonald, 1992
  21. Annual bluegrass control Preemergence Control Barricade, Pendulum Surflan, Dimension Balan, Ronstar Kerb Atrazine, Simazine annual bluegrass Boat shaped leaf tip
  22. Preemergence Herbicides Need rainfall or irrigation (1/2 inch) Do not control emerged weeds
  23. Preemergence Herbicides If irrigation is not available, apply well in advance of expected weed germination to allow for an activating rainfall. Loss of activity may occur if they are not watered in within 7 to 10 days. Losses from photodecomposition and volatilization Treflan (Team) is the most volatile, Barricade the least volatile.
  24. Relative Solubility of Preemergence Herbicides
  25. Preemergence Herbicide Volatility
  26. Irrigation Timing and Formulation Effect on Crabgrass Control with Pendimethalin GR = granular, WP = Sprayable 0 = watered in immediately 7 = watered in 7 days after application
  27. Granular Formulations Poor Distribution of Active Ingredients: Spreader not calibrated, changes with age Bag settings are only guidelines Spreader and/or product cause a skewing of product distribution over the turf Particle size too large for uniform coverage Lower application rates reduce uniform coverage
  28. Fertilizer/Preemergence Products Correct fertilizer analysis?? Time of year?? N-release characteristics?? Supplemental fertilizer applications?? Supplemental herbicide applications??
  29. Fertilizer/Preemergence Products - Other Considerations Uniform coverage required Uniform particle size is important Release characteristics of fertilizer product Control equivalent to sprayable and granular products
  30. Preemergence Herbicides - Formulation Effects Yelverton, et al., 1996
  31. Preemergence Herbicides - Formulation Effects Johnson and Murphy, 1991
  32. Preemergence Herbicides- Formulation Effects Johnson and Murphy, 1991
  33. Preemergence Herbicide Timing Soil temperatures can vary in a neighborhood - south facing slopes warm earlier in the Spring Coarse textured soils warm more quickly than fine-textured soils Most preemergence herbicides are degraded by soil microorganisms - activity is less at 45 degree vs. 70 degree soil temp. Most warm-season grassy weeds germinate at 55 to 65 F. APPLY EARLY Can the site be irrigated for activation?
  34. Suggested Application Dates North Georgia Spring, March 1 - 20 Fall, August 20 - Sept. 15 South Georgia Spring, Feb. 10 - March 1 Fall, Sept. 20 - Oct. 15 Early is always better than late!
  35. Timing Summer Annual Grass Control Late February to early March for crabgrass control Goosegrass two to four weeks later Early application (late January, February) is OK due to slower herbicide decomposition during cool weather.
  36. Repeat Applications - Summer Space 8 to 10 wks apart Apply 1/2 X fb 1/2X May improve control of crabgrass and goosegrass
  37. Guidelines - Preemergence Labeled products only Established turfgrass Apply before weed emergence Need rainfall or irrigation within 5 days Consider split applications Delay mowing until after incorporation Know future plans
  38. Lack of Preemergence Herbicide Performance Applied after weed emergence No rainfall or irrigation Excessive rain after application, high rainfall year High rainfall year Poor site drainage Drought Rate too low Mow/Bag before incorporation
  39. Broadleaf Control Most broadleaf control is done with postemergence herbicides. The essential broadleaf herbicides are: Postemergence - growth regulators and sulfonylureas Pre and post – atrazine, simazine, metribuzin. Pre only - Gallery
  40. Growth Regulator Herbicides
  41. Broadleaf Herbicides There are many growth regulator combinations on the market. Mixtures of broadleaf-active herbicides tend to control more weed species than each individual component herbicide.
  42. Phenoxy + Dicamba Herbicides
  43. Phenoxy + Dicamba Herbicides
  44. Phenoxy, Dicamba, Picolinic Herbicides
  45. Post Herbicide Use Guidelines Try to avoid spraying warm-season grasses during transition. Shade grasses are less herbicide tolerant than grasses growing in full sun. Spray when wind speeds are less than 5 mph.
  46. Post Herbicide Use Guidelines Avoid stress conditions (> 90 F.) Avoid spring transition on warm-seasons Repeat applications Do not mow 24 to 48 hours before or after application Rainfall and irrigation effects
  47. Post Herbicide Use Guidelines Do not water for 12-24 hours. Need a rain free period of at least 6 hours. Avoid extreme temperatures. Apply when temperatures are between 40 and 80°F.
  48. Examples of Rain-Free Periods MSMA - 24 hours Trimec Classic - 24 hours Basagran T/O - 8 hours Finale - 4 hours Vantage - 1 hour
  49. Post Herbicide Use Guidelines Annual weed control is excellent in the seedling stage and poor as the weed matures Perennial weeds are more susceptible in the Spring or Fall because root reserves are usually depleted and the weed has less recovery potential Apply to actively growing weeds - the cuticle is more easily penetrated Sprays give better control than granules.
  50. Post Herbicide Use Guidelines Repeat applications are most effective for tough perennials. Apply during good growing conditions when adequate soil moisture is present. Add a surfactant if called for on label.
  51. Non-Target Plants Check for restrictions on the use of herbicides around trees and shrubs. Be very careful around vegetables and ornamentals with growth regulator herbicides. Avoid applying dicamba and atrazine under shallow rooted ornamentals such as azalea and rhododendron.
  52. Nonselective Broadleaf Control Roundup Pro - slow acting (7-14 days) but provides the best control of perennials. Reward - fastest burndown, poor perennial control, poor grass control. Finale - Almost as fast as Reward, will leave a straight edge, very good on white clover and other legumes. Not good on perennials.
  53. Lack of Post Herbicide Performance Environmental stresses Weed growth stage Rain/irrigation wash-off No adjuvant Poor spray coverage
  54. Lack of Post Herbicide Performance Wrong rate Wrong herbicide No follow-up application Mowing effects