Extending the Residual Length of Preemergence Herbicides and Summer Annual Weed Control

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Extending the Residual Length of Preemergence
Herbicides and Summer Annual Weed Control

• Patrick McCullough, Ph.D.
• Extension Turf Weed Scientist, UGA
• Coastal Green Conference, Savannah, GA
• May 14, 2009

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Goosegrass
Crabgrass
Summer Annuals
Common Purslane
Spotted Spurge
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Summer Weed Control

• Evaluate turf cultural practices
• Mowing height
• Irrigation
• Failure to control winter weeds
• Mowing height
• Turf mowed too low may have reduced vigor and
  stress tolerances.
• Raise mowing height to improve turf competition
  with weeds.

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Mowing Height Effect on Smooth Crabgrass
Incidence in Tall Fescue
Crabgrass Cover ()
Mowing Height
Source Hoyle et al. 2008
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Weed Populations are Influenced by Irrigation
How much water? How frequently?
Picture credit www.jonnynichols.com/Irrigation.h
tml
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Influence of irrigation frequency on average
dollarweed occurrence in St. Augustinegrass over
3 years in Florida.
Dollarweed Cover ()
Irrigation Frequency
Busey and Johnston. 2006. Weed Science
54(5)961-967
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Common Bermudagrass in Griffin, GA March 20, 2009
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Common Bermudagrass in Griffin, GA March 20, 2009
Annual Bluegrass/ Bermudagrass (dormant)
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Common Bermudagrass in Griffin, GA May 13, 2009
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Common Bermudagrass in Griffin, GA May 13, 2009
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Common Bermudagrass in Griffin, GA May 13, 2009
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TifSport Bermudagrass in Griffin, GA May 13,
2009
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Know Your Weeds
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Books for Weed ID
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Summer Annual Weed Control

• Weeds targeted in spring Summer annuals
• Crabgrass, goosegrass, broadleaf weeds
• Lifecycle is predictable
• Apply preemergence herbicides before
  establishment
• Weeds not controlled by PREs
• Weeds present in turf
• Perennial weeds established from vegetative
  reproduction (sedges, white clover, etc.)

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Turfgrass Preemergence Herbicides
Herbicides are available under a wide variety of
trade names, sprayable and granular formulations,
and may be impregnated on fertilizer
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Preemergence Turfgrass Herbicides

• Absorbed by the roots and shoots of germinating
  summer-annual weeds.
• Weed control is influenced by herbicide
  concentration in the soil seedbank (top ¼ to 1/3
  inch of the soil).
• Herbicides placed below or above (on leaf tissue)
  the seedbank will be ineffective on germinating
  weeds.
• Turfgrass safety is a function of herbicide
  placement.
• Herbicides have low water solubility and are not
  able to leach down into turfgrass root zone (ex.
  Siduron).
• If turfgrass injury occurs it is generally
  inhibition of lateral root or stem development.

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PREs
Preemergence herbicides do not prevent
germination.
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Preemergence Turfgrass Herbicides

• Absorption of preemergence herbicides by weeds is
  influenced by
• Soil texture (sand, silt, and clay content)
• Soil moisture
• Herbicide chemistry
• Persistence in soil is key to residual activity
• Leaching or movement in soil by water
• Rate of microbial breakdown

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Temperature and Microbial Activity
High
Low
Spring
Summer
Fall
High
(Herbicide Concentration)
Low
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PREs
Preemergence herbicide movement out of seedbank
will reduce efficacy for controlling weeds.
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PREs
Preemergence herbicide movement out of seedbank
will reduce efficacy for controlling weeds.
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Preemergence Turfgrass Herbicides

• Soil microbial activity
• Major contributor to loss of herbicides in
  summer,
• Increases with soil temperature,
• Herbicide concentration may decline from spring
  to summer which inhibits efficacy for weed
  control.
• Worst case scenario
• Sandy soil,
• Above average soil temperatures in spring,
• Heavy rainfall,
• Extended weed germination cycle.

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Preemergence Turfgrass Herbicides

• Application Timing
• Before weeds germinate or establish
• High enough concentration to control germination
• Initial Germination Timing
• Crabgrass 55 to 60 soil temperature
• Goosegrass 60 to 65 soil temperature
• If targeting goosegrass only, applications may be
  delayed three to four weeks.

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March 1 to April 1
March 1 to 20
January 1 to March 1
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Preemergence Turfgrass Herbicides

• Application Timing
• These dates should be considered general
  recommendations
• Must consider environmental factors such as soil
  temperature, rainfall, and germination cycles
  from previous years.
• Contact local county extension agents for advice
  on initiating preemergence herbicide programs.
• Length of Residual Control
• Vary depending on use rate, soil, and
  environmental conditions

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Non-Irrigated Sites
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What if I dont have irrigation?
Picture credit www.jonnynichols.com/Irrigation.h
tml
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Preemergence Herbicide Use on
Non-Irrigated Turf

• Preemergence herbicides require activation
• Rainfall or irrigation is critical following
  treatments
• Generally not a concern with initial preemergence
  herbicide treatments in early spring due to
  sufficient rain
• More of a concern with split applications
• Return clippings to non-irrigated turf

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Preemergence Herbicide Use on
Non-Irrigated Turf

• Return clippings to non-irrigated turf
• Reduces retention of herbicide on leaf tissue to
  get in soil
• Wait to collect clippings until at least half to
  one inch of rainfall is received.
• Apply liquid formulations in high water volume
• gt100 gallons per acre
• Reduces foliar contact and increases soil water
  concentration

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Pendimethalin2 lbs a.i./acre
Not Irrigated
Irrigated
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Dimension 0.25 lbs a.i./acre
Irrigated
Not Irrigated
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Preemergence Herbicide Use on
Non-Irrigated Turf

• Use a dry granule formulation
• Advantages May be easier to apply and
  incorporate in to soil than liquid formulations
• Disadvantages Coverage may lack uniformity
• Apply when dew is not present on turf
• Herbicide plus Fertilizer Products
• Weed and Feed sold as granular formulations
• Check herbicide and fertilizer rates when you
  apply

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Irrigation timing and pendimethalin formulation
influence crabgrass control
Crabgrass Plants/sq ft
Irrigation Timing
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Irrigation timing and pendimethalin formulation
influence crabgrass control
Crabgrass Plants/sq ft
Irrigation Timing
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No Irrigation
Dry Granule
Sprayable (WP)
Herbicide loss
Photodegredation Volatilization
Clipping collection
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Preemergence Herbicide Use on
Non-Irrigated Turf

• Weed and Feed Products
• Advantages Apply both preemergence herbicides
  and spring fertilizer at same time
• Disadvantages Concentrations may be
  insufficient for management levels
• Read and follow directions to determine if these
  products are suitable for your management regime
  or turf species.

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Preemergence Herbicides

• Why Applications Fail in Summer

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Why Preemergence Herbicides Fail

• Herbicide persistence in soil determines
  capability to control weed germination.
• Extended germination cycles of weeds
• Caused by drought, heat, and seed dormancy
• Two major germination periods
• Dormant weed seeds germinate later in summer upon
  rainfall

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Germination Flush 1
Germination Flush 2
Spring
Summer
Fall
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(Drought followed by heavy rainfall)
Spring
Summer
Fall
Germination Flush 1
Germination Flush 2
Spring
Summer
Fall
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(Drought followed by heavy rainfall)
Spring
Summer
Fall
Germination Flush 1
Germination Flush 2
Spring
Summer
Fall
High
(Herbicide Concentration)
Low
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Temperature and Microbial Activity
High
Low
Spring
Summer
Fall
High
(Herbicide Concentration)
Low
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Extending Residual Activity

• If applied at the same time, and environmental
  and site conditions are equal, initial herbicide
  activity may be similar.
• Exceptions
• Betasan and Tupersan have less potential to
  control goosegrass compared to Ronstar.
• Dimension (all formulations) will provide some
  control of small, untillered crabgrass.

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Extending Residual Activity
Longest Moderate Shortest
Residual of individual herbicides is dependent on
use rate, soil, and environmental factors.
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Extending the Length of Crabgrass Control

• Apply split applications 6-8 weeks apart
• For example, Dimension 1.0 EC at 1.5 qt/A,
• In March, apply 1.0 qt/acre
• In June, apply 0.5 qt/acre.

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Temperature and Microbial Activity
High
Low
Spring
Summer
Fall
High
Single app
(Herbicide Concentration)
Low
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Temperature and Microbial Activity
High
Low
Spring
Summer
Fall
Sequential
High
Single app
(Herbicide Concentration)
Low
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Crabgrass Control in August 2004
Crabgrass Control
Dimension 40WP (20 oz/acre Total)
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Crabgrass Control in August 2005
Crabgrass Control
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August - 2005
Dimension 20 oz/A
Dimension 10 oz/A -split
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Reseeding Restrictions
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Reseeding Restrictions
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Dithiopyr

• Trade Name Dimension (40WP, 2EW, 1EC)
• Pyridine herbicide
• Cell division inhibitor, similar to
  dinitroanalines
• Effective preemergence herbicide for annuals
• Early postemergence activity on untillered
  crabgrass (for irrigated sites)
• Delay PRE applications after crabgrass
  germination.
• Use if initial preemergence applications were
  missed.

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Crabgrass control after three weeks from early
postemergence treatments in Griffin, GA, 2009.
Control ()
Dimension Rate (lb a.i./acre)
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TifSport Bermudagrass Injury Two Months After
Preemergence Dimension Applications on March 9,
2009, Griffin, GA.
Dimension 40WP
Dimension 2EW
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Tifsport bermudagrass injury from March
preemergence Dimension treatments after two
months, Griffin, GA, 2009.
Injury ()
Dimension Rate (lb a.i./acre)
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Extending the Length of Summer Annual Weed Control

• Use a PRE with a POST herbicide
• Tank mix residual herbicide with a POST herbicide
  in May.
• May be able to reduce rate of residual herbicide
  Only on irrigated sites
• Concerns
• Do not apply Acclaim with broadleaf weed
  herbicides or within 14 d of a BLW herbicide
  application

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Tenacity plus Barricade Applied June
14 (Early post Residual)
Tenacity Barricade
Untreated
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Quinclorac

• Trade name Drive (75 DF)
• Used in turf for crabgrass and broadleaf weed
  control.
• Has residual soil activity for 20 to 30 days.
• Compatible with broadleaf weed herbicides.
• New Formulation Drive XLR8 (1.5 SL)
• New Combination Products One-Time, Q4.

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Tifsport Bermudagrass Two Weeks after Drive
Application on 4/16/09, Griffin, GA
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TifSport Bermudagrass Injury from Drive
After Three Weeks in Griffin, GA
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Common Centipede/Poa annua Two Weeks after
Drive Application on 4/16/09, Griffin, GA
Drive 75DF
0.75 lb a.i./acre
Untreated
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Growth Stage of Weeds Influences Herbicide
Efficacy
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Acclaim Xtra 20 oz/A 40 GPA
03 Flat Fan
03 Flood Jet
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Crabgrass Controlled - November
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Large Crabgrass with Seedhead
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Drive 1.0 lb/A 1 WAT
Picture taken Sept. 5, 2003
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TREATED
UNTREATED
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Preemergence Herbicide Use During Sod
Installation
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Preemergence Herbicide Use During Sod
Installation

• Sod should be rooted and actively growing before
  PRE applications
• Sod growth inhibition
• DNA herbicides, inhibit root growth
• Examples pendimethalin, prodiamine, dithiopyr
  (pyridine)
• Oxadiazon (Ronstar, Starfighter)
• Protox inhibitor
• Does not inhibit root growth.

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Rooting of Bermudagrass Sod Treated with PREs One
Month After Installation
2 Months After Treatment
Root Reductions ( of Untreated)
Murphy and Waltz, UGA. 2002.
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Mesotrione

• Trade name Tenacity
• Inhibits p-Hydroxyphenyl pyruvate dioxygenase
  (HPPD)
• Triketone herbicide family.
• Previously registered for use in corn (Callisto)
• Registered in 2008 for golf courses and sod farms
• Systemic preemergence and postemergence herbicide
  for selective and residual weed control.

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Mesotrione (4SC) Rates for Use During Turf
Establishment
St. Augustine grown for sod only
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Bleaching of crabgrass following a Tenacity
application
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Tenacity
0.25 lb ai/acre
Untreated
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Mesotrione
Source Tenacity Herbicide label. 2008.
Syngenta Corp.
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Tenacity for Crabgrass Control

• Preemergence and postemergence crabgrass control,
• Residual activity may not be sufficient for
  season long control,
• Potential to provide a unique product concept
  early post application in combination with
  residual herbicide (Barricade),
• Activity depends on crabgrass growth stage.

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Considerations for Late Summer

• Evaluate turfgrass cultural practices
• Prepare to control winter annual weeds
• Preemergence program
• Collect clippings if seedheads are present
• Prepare to control fall pathogens/turf diseases

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MSMA Update
Dallisgrass
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MSMA Update

• On January 16, 2009, the MAA Research Task Force
  signed an agreement with the U.S. Environmental
  Protection Agency, which permits the continued
  use of MSMA.
• MSMA use on selected turf areas will continue
  until December 31, 2013.

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MSMA Update

• Golf Courses
• One application to newly constructed courses.
• For existing courses, spot treatment (100 sq ft
  per spot), not to exceed 25 of the total course
  in one year.
• Sod Farms
• Two broadcast applications will be allowed per
  crop.
• A 25 foot buffer strip will be required for those
  fields bordering permanent water bodies.

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MSMA Update

• Highway Right of Ways
• Two broadcast applications will be allowed per
  year.
• A 25 foot buffer strip will be required for those
  fields bordering permanent water bodies.
• MSMA can be applied until December 31, 2010
• Residential turf
• Athletic fields

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Dallisgrass Control
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MSMA Update

• In 2012 EPA will reevaluate the risk posed by
  inorganic arsenic.
• MSMA use will continue beyond 2013 should the
  review result in a conclusion that there is no
  health concern at the doses of exposure resulting
  from the relevant uses.

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Questions?