Post on 13-Jan-2016
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Turfgrass Herbicide Use Characteristics
Tim R. Murphy
The University of Georgia
Preemergence herbicides are the foundation of annual grass control.
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.
Preemergence Options
Atrazine Pendimethalin Simazine Kerb Balan Dimension XL Bensulide TeamPro Pennant Surflan Gallery Barricade Ronstar
The majority of herbicides used for preemergence annual grass control are dinitroanilines and dithiopyr
DNA’s Barricade Pendulum Surflan Balan TreflanDimension
Best used on established turf.
Mitotic inhibitors. Immobile in the
soil
Ronstar (oxadiazon)
Not a mitotic inhibitorPreferred herbicide for sprigging or high
traffic areas (athletic fields, tees, etc.)Preferred herbicide for preemergence
goosegrass controlWill control crabgrass but is more effective
on goosegrass
What is the best preemergenceherbicide for turfgrasses??
It depends……….
Preemergence Herbicide Selection
Turfgrass speciesWeed speciesImmature vs. establishedTime of yearIrrigation capabilitiesRenovation plans
Preemergence Herbicide Selection
Granular or spray equipmentDesired control levelApplication frequencyOrnamental toleranceCost??
Annual Grass Control Ratings
Herbicide
Crabgrass
Goosegrass
Annual Bluegrass
Benefin G F G-E Benefin + oryzalin G-E F-G G-E Benefin + trifluralin F-G F G-E Bensulide E P P-F Dithiopyr G-E F-G G-E Oryzalin G-E F-G G-E Oxadiazon G G-E G-E Pendimethalin G-E F-G G-E Prodiamine G-E F-G G-E
Crabgrass spp.
Summer annualAt least 5 species in GA (tropical, smooth,
large, southern, blanket)Germinates at soil temps. - 53 to 58 F., 4
inch depthLight required
Southern crabgrass
Smooth crabgrass
Goosegrass
Summer annualGerminates - soil temp. 4 inch depth
averages 60 to 65 F.Usually germinates 2 to 6 weeks later than
crabgrassLight required
goosegrass
Summer annual Prefers compacted areas that
are overwatered
goosegrasscrowfootgrass
Goosegrass Cultural Controls
Aerify to alleviate compaction Redirect trafficControl wateringEncourage dense turf
Core Aerification
Previously thought to break up herbicide layer and reduce weed control
Research shows little increased crabgrass or goosegrass due to core aerification
Annual bluegrass
Winter annualGerminates late summer-fall at soil
temperatures around 70 F.Second germination flush in mid- to late-
winter
Continuous annual bluegrass seedgermination occurred from mid-Nov.through early January in Knoxville, TN.
Callahan and McDonald, 1992
Annual bluegrass control
Preemergence Control Barricade, Pendulum Surflan, Dimension Balan, Ronstar Kerb Atrazine, Simazineannual bluegrass
Boat shaped leaf tip
Preemergence Herbicides
Need rainfall or irrigation (1/2 inch)Do not control emerged weeds
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.
Relative Solubility of Preemergence Herbicides
0.275 0.30.013
0.7
2.6
0
1
2
3
4
5
Surflan Ronstar Pendimet Treflan Barricade
ppm
Preemergence Herbicide Volatility
Herbicide
Vapor Pressure (mm Hg)
Relative Volatility
Benefin 1.0X 10-5 Moderate
Pendimethalin 9.4 X 10-6 Low
Surflan 2.5 X 10-8 Very Low
Barricade 3.3 X 10-9 Very Low
Dimension 4.0 X 10-6 Low
Kerb 8.5 X 10-5 Moderate
Bensulide 8.0 X 10-7 Very Low
Ronstar 7.8 X 10-7 Very Low
Aatrex 2.9 X 10-7 Very Low
Irrigation Timing and Formulation Effect on Crabgrass Control with Pendimethalin
0
5
10
15
20
25
30
35
40
45
Pla
nts/
sq.
ft.
GR 0 WP 0 GR 7 WP 7
GR = granular, WP = Sprayable
0 = watered in immediately
7 = watered in 7 days after application
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
Fertilizer/Preemergence Products
Correct fertilizer analysis??Time of year??N-release characteristics??Supplemental fertilizer applications??Supplemental herbicide applications??
Fertilizer/Preemergence Products - Other Considerations
Uniform coverage requiredUniform particle size is importantRelease characteristics of fertilizer productControl equivalent to sprayable and
granular products
Preemergence Herbicides - Formulation Effects
Barricade
lbs. ai/acre
Smooth Crabgrass Control (%)
65WG 0.75 98
0.29G 0.75 91
0.5G 0.75 81
Yelverton, et al., 1996
Preemergence Herbicides- Formulation Effects
% Control
Dimension
lbs. ai/acre
Smooth Crabgrass
Goosegrass
1EC 0.5 64 31
1EC 0.75 91 29
0.25G 0.25 82 55
0.25G 0.38 100 78
0.25G 0.5 100 82 Johnson and Murphy, 1991
Preemergence Herbicides- Formulation Effects
% Control
Dimension
lbs. ai/acre
Large Crabgrass
Goosegrass
1EC 0.25 + 0.25 88 72
18-3-12G 0.25 + 0.25 96 94
Johnson and Murphy, 1991
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?
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!
Timing Summer Annual Grass Control
Late February to early March for crabgrass control
Goosegrass two to four weeks laterEarly application (late January, February) is
OK due to slower herbicide decomposition during cool weather.
Repeat Applications - Summer
Space 8 to 10 wks apartApply 1/2 X fb 1/2XMay improve control of crabgrass and
goosegrass
Guidelines - Preemergence
Labeled products onlyEstablished turfgrassApply before weed emergenceNeed rainfall or irrigation within 5 daysConsider split applicationsDelay mowing until after incorporationKnow future plans
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
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
Growth Regulator Herbicides
Phenoxy Picolinic Acid Benzoic Acid
2,4-D Lontrel Banvel
dichlorprop Turflon D Vanquish
mecoprop
MCPA
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.
Phenoxy + Dicamba Herbicides
Herbicide 2,4-D MCPP MCPA 2,4-DP dicamba
Weedar 64 X
MCPP-4 X
2 Plus 2 X X
Four Power + X X
Turf D + DP X X
Trimec Classic X (>) X (<) X
Trimec Southern X (<) X (>) X
Phenoxy + Dicamba Herbicides
Herbicide 2,4-D MCPP MCPA 2,4-DP dicamba
Triamine X X X
Triamine II X (>) X (<) X
Tri-Power X (<) X (>) X
Dissolve X X X
Triplet X (>) X (<) X (>)
Triplet Sens. X (<) X (>) X (<)
Phenoxy, Dicamba, Picolinic Herbicides
Herbicide 2,4-D MCPA clopyralid triclopyr dicamba
Lontrel X
Turflon Ester X
Confront X X
Chaser (ester) X X
Chaser II Am. X X
Cool Power (ester)
X (<) X (<) X (<)
HorsePower X (>) X (>) X (>)
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.
Post Herbicide Use Guidelines
Avoid stress conditions (> 90 F.)Avoid spring transition on warm-seasonsRepeat applicationsDo not mow 24 to 48 hours before or after
applicationRainfall and irrigation effects
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.
Examples of Rain-Free Periods
MSMA - 24 hoursTrimec Classic - 24 hoursBasagran T/O - 8 hoursFinale - 4 hoursVantage - 1 hour
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.
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.
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.
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.
Lack of Post Herbicide Performance
Environmental stressesWeed growth stageRain/irrigation wash-offNo adjuvantPoor spray coverage
Lack of Post Herbicide Performance
Wrong rateWrong herbicideNo follow-up applicationMowing effects