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AUTHOR
Dr. Tim R. Murphy
Extension Weed Scientist
University of Georgia
Griffin, GA

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TABLE OF CONTENTS
  1. Turfgrass Weed Management
  2. The Goal
  3. Turfgrass Weeds
  4. Develop A Plan
  5. Weed Management Strategy
  6. Identify the Weed Problem
  7. Weed Life Cycles
  8. Weeds can be a problem in all 12 months
  9. Integrated Weed Management
  10. Preventive Methods
  11. Cultural Methods
  12. Soil Fertility Effects on Weeds
  13. Weeds Favored in Compacted Soils
  14. Weeds Favored by High Soil Moisture
  15. Weeds Favored by Low Soil Moisture
  16. Maintain Healthy Turfgrass
  17. Preemergence herbicides are the foundation of annual grass control.
  18. Preemergence herbicides do not prevent weed seeds from germinating
  19. Preemergence Options
  20. The majority of herbicides used for preemergence annual grass control are dinitroanilines and dithiopyr.
  21. What is the best preemergence herbicide for turfgrasses??
  22. It depends...
  23. Preemergence Herbicide Selection
  24. Preemergence Herbicide Selection
  25. Annual Grass Control Ratings
  26. Crabgrass spp.
  27. Crabgrass spp.
  28. Southern and Smooth Crabgrass
  29. Goosegrass
  30. Goosegrass
  31. Goosegrass and crowfootgrass
  32. Goosegrass Cultural Controls
  33. Core Aerification
  34. Ronstar (oxadiazon)
  35. Annual bluegrass
  36. Continuous annual bluegrass seed germination occurred from mid-Nov through early January
  37. Annual bluegrass control
  38. Preemergence Herbicides
  39. Preemergence Herbicides
  40. Irrigation Timing and Formulation Effect on Crabgrass Control with Pendimethalin
  41. Relative Volatility of Preemergence Herbicides
  42. Relative Solubility of Preemergence Herbicides
  43. Granular Formulations
  44. Fertilizer/Preemergence Products
  45. Fertilizer/Preemergence Products - Other Considerations
  46. Preemergence Herbicides - Formulation Effects
  47. Preemergence Herbicides - Formulation Effects
  48. Preemergence Herbicides - Formulation Effects
  49. Preemergence Herbicide Timing
  50. Suggested Application Dates
  51. Timing Summer Annual Grass Control
  52. Repeat Applications - Summer
  53. Guidelines - Preemergence
  54. Lack of Preemergence Herbicide Performance
  55. Post Summer Grass Control
  56. MSMA Use
  57. MSMA Alternatives
  58. MSMA Alternatives
  59. Post Goosegrass Control
  60. Poa Control with Kerb
  61. Annual Bluegrass Control
  62. Ryegrass
  63. Ryegrass Control
  64. Ryegrass
  65. Tall Fescue
  66. Dallisgrass Control
  67. Sandbur
  68. Bermuda Suppression in Zoysia
  69. Roundup Rate and Bermudagrass Control
  70. Bermuda Control with Roundup – 1 yr.
  71. Bahiagrass
  72. Avoiding Phytotoxicity
  73. Avoiding Phytotoxicity



SLIDE CONTENTS
  1. Turfgrass Weed Management I. Methods II. Grass Weed Control Tim R. Murphy Crop and Soil Sciences The University of Georgia
  2. The Goal Establish and maintain a high quality, nearly weed-free turfgrass.
  3. Turfgrass Weeds Reduce quality Reduce density Decrease aesthetic value or utility of the turfgrass.
  4. Develop A Plan Goals Economics Alternatives Benefits
  5. Weed Management Strategy Diagnose problem Evaluate control methods Select program Execute program Evaluate
  6. Identify the Weed Problem READ textbooks and periodicals Keep a diagnostic tool kit - hand lens, etc. Know the life cycle of the pest (What temp. does a specific weed seed germinate?) Is the weed the cause or effect of the problem? Confirm your diagnosis
  7. Weed Life Cycles Summer annuals - < 1 yr. Winter annuals - ə yr. Biennials - 2 yr. Perennials - > 2 yr.
  8. PPT Slide Weeds can be a problem in all 12 months.
  9. Integrated Weed Management Preventive Cultural Biological Mechanical Herbicides
  10. Preventive Methods State and federal laws Weed-free seed, plant material Topsoil (no nutsedge) Clean equipment Field borders
  11. Cultural Methods Adapted turfgrasses Fertility management Cultivation practices Irrigation Pest control
  12. Soil Fertility Effects on Weeds Low N - legumes, mosses High P - annual bluegrass High N - common chickweed Low soil pH - red sorrel, broomsedge
  13. Weeds Favored in Compacted Soils Annual bluegrass Goosegrass Prostrate knotweed Common lespedeza Path rush
  14. Weeds Favored by High Soil Moisture Sedges - purple nutsedge, green kyllinga Rushes Annual bluegrass Mosses
  15. Weeds Favored by Low Soil Moisture Prostrate spurge Poorjoe Common lespedeza Prostrate knotweed
  16. Maintain Healthy Turfgrass Manage the roots to have good shoots Soil testing is a must! Utilize cultural practices (fertility, irrigation, mowing height, etc.) to improve stress tolerance Keep mower blades sharp ! Use the best species and cultivars for your location
  17. Preemergence herbicides are the foundation of annual grass control.
  18. PPT Slide 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.
  19. Preemergence Options
  20. 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. Relatively immobile in the soil
  21. PPT Slide What is the best preemergence herbicide for turfgrasses??
  22. PPT Slide It depends……….
  23. Preemergence Herbicide Selection Turfgrass species Weed species Immature vs. established Time of year Irrigation capabilities Renovation plans
  24. Preemergence Herbicide Selection Granular or spray equipment Desired control level Application frequency Ornamental tolerance Cost??
  25. Annual Grass Control Ratings
  26. 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
  27. PPT Slide Summer annual Crabgrass spp.
  28. PPT Slide Southern crabgrass Smooth crabgrass
  29. 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
  30. goosegrass Summer annual Prefers compacted areas that are overwatered
  31. PPT Slide goosegrass crowfootgrass
  32. Goosegrass Cultural Controls Aerify to alleviate compaction Redirect traffic Control watering Encourage thick turf
  33. Core Aerification Previously thought to break up herbicide layer and reduce weed control Research shows little increased crabgrass or goosegrass due to core aerification
  34. 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
  35. Annual bluegrass Winter annual Germinates late summer-fall at soil temperatures around 70 F. Second germination flush in mid- to late-winter
  36. PPT Slide Continuous annual bluegrass seed germination occurred from mid-Nov. through early January in Knoxville, TN. Callahan and McDonald, 1992
  37. Annual bluegrass control Preemergence Control Barricade, Pendulum Surflan, Dimension Balan, Ronstar Kerb Atrazine, Simazine annual bluegrass Boat shaped leaf tip
  38. Preemergence Herbicides Need rainfall or irrigation (1/2 inch) Do not control emerged weeds
  39. 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. Treflan (Team) is the most volatile, Surflan the least volatile. Losses from photodecomposition and volatilization
  40. Irrigation Timing and Formulation Effect on Crabgrass Control with Pendimethalin GR = granular, 0 = watered in immediately WP = Sprayable, 7 = watered in 7 days after application
  41. Relative Volatility of Preemergence Herbicides
  42. Relative Solubility of Preemergence Herbicides
  43. 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
  44. Fertilizer/Preemergence Products Correct fertilizer analysis?? Time of year?? N-release characteristics?? Supplemental fertilizer applications?? Supplemental herbicide applications??
  45. 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
  46. Preemergence Herbicides - Formulation Effects Yelverton, et al., 1996
  47. Preemergence Herbicides - Formulation Effects Johnson and Murphy, 1991
  48. Preemergence Herbicides- Formulation Effects Johnson and Murphy, 1991
  49. 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?
  50. 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!
  51. Timing Summer Annual Grass Control Late February to early March for Georgia crabgrass control Goosegrass two to four weeks later Early application (late January, February) is OK due to slower herbicide decomposition during cool weather.
  52. Repeat Applications - Summer Space 8 to 10 wks apart Apply 1/2 X fb 1/2X May improve control of crabgrass and goosegrass
  53. 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
  54. 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
  55. Post Summer Grass Control MSMA is the most commonly used product in bermudagrass, tall fescue and zoysiagrass for crabgrass control Do not use MSMA on centipedegrass or St. Augustinegrass MSMA labeled for tall fescue but may cause severe injury during hot Georgia summers
  56. MSMA Use Most effective on seedling to 4 leaf crabgrass Apply when temperature is between 75 and 90°F. Repeat application(s) usually needed on well tillered crabgrass
  57. MSMA Alternatives Vantage (sethoxydim) is a grass specific herbicide Vantage may be used on centipedegrass Vantage is most effective on seedling to 4 leaf grasses Envoy (clethodim) may also be used, but only on centipedegrass sod farms
  58. MSMA Alternatives Acclaim Extra (fenoxaprop) and Fusilade II (fluazifop) are grass specific herbicides Acclaim Extra and Fusilade II may be used on zoysiagrass and tall fescue They are most effective on seedling grasses
  59. Post Goosegrass Control Illoxan (diclofop) will control goosegrass postemergence For use on bermudagrass golf courses only Close mowed (less than 1 inch) goosegrass is easier to control MSMA + Sencor will control goosegrass but causes more bermudagrass injury
  60. Poa Control with Kerb Excellent for annual bluegrass Will move with water and damage cool-season grasses Herbicide of choice for late spring Poa control after bermuda has greened up Kerb movement onto bentgrass
  61. Annual Bluegrass Control Bentgrass Greens One option is use of paclobutrazol (Trimmit) at 0.25 lb/ac in the fall followed by 2 to 3 applications in the spring. Pre’s tend to select for the perennial type Poa annua
  62. PPT Slide Roundup is the most effective Kerb will provide some help Illoxan will provide some control Reward and Finale ineffective Ryegrass
  63. Ryegrass Control
  64. PPT Slide Overseeding Clumpy ryegrass
  65. tall fescue cool-season perennial Roundup High rates of Kerb during winter months Corsair
  66. Dallisgrass Control Repeat applications of MSMA Usually 3 to 4 treatments required on a weekly schedule or spot spray with Roundup
  67. PPT Slide summer annual Sandbur spp.
  68. Bermuda Suppression in Zoysia Completely eradicate bermuda before planting zoysia and then buy clean zoysia Spot spray with Roundup Apply 3 to 4 applications of Acclaim Extra per year for 2 years Apply 2 applications of Fusilade II per year for 2 years
  69. Roundup Rate and Bermudagrass Control DAT = Days after Treatment
  70. Bermuda Control with Roundup – 1 yr.
  71. PPT Slide rhizome seedhead bahiagrass Repeat MSMA, or Manor
  72. Avoiding Phytotoxicity Read the label to make sure the herbicide is registered for use on the turf or plant Apply the herbicide at the recommended rate and determine application intervals Test unfamiliar products and tank mixes on a small scale Use separate sprayers for fungicides or clean thoroughly between applications
  73. Avoiding Phytotoxicity Keep sprayers calibrated and in good working order Agitate spray mixture Avoid application to stressed turfgrasses Keep accurate records of all applications