Maximizing Preemergence Herbicide Performance in Tall Fescue Tim R. Murphy The University of...
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Transcript of Maximizing Preemergence Herbicide Performance in Tall Fescue Tim R. Murphy The University of...
Maximizing Preemergence Herbicide Performance in Tall Fescue
Tim R. Murphy
The University of Georgia
Tall Fescue/Southern Transition Zone
• Growth slows in high heat and humidity
• Susceptible to brown patch (only limited resistance in commercial varieties)
• Turf density decreases with resultant decrease in competitive ability
• Often reseeded annually or every other year
Differential large crabgrass control in tall fescue. Johnson, 1993
Large Crabgrass
Herbicide RateCommonbermuda Tall fescue
(lbs ai/acre) ----------(%)-----------
Pendimethalin 3.0 96* 531.5 + 1.5 91* 45
Oxadiazon 4.0 97 971.0 + 1.0 96 93
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 for Tall Fescue
Balan PendimethalinXL DimensionTeamPro BensulideSurflan GalleryBarricade Ronstar
Annual Grass Control Ratings
Herbicide Crabgrass GoosegrassAnnualBluegrass
Benefin G F G-EBenefin + oryzalin G-E F-G G-EBenefin + trifluralin F-G F G-EBensulide E P P-FDithiopyr G-E F-G G-EOryzalin G-E F-G G-EOxadiazon G G-E G-EPendimethalin G-E F-G G-EProdiamine G-E F-G G-E
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.
• Trifluralin is the most volatile, Surflan the least volatile.• Losses from photodecomposition and volatilization
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, 0 = watered in immediately
WP = Sprayable,
7 = watered in 7 days after application
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 !
Brown Patch in Tall Fescue
• Rhizoctonia solani
• Favored by night temps. > 60 F. and > 10 hrs., foliar wetness for several days
• Cloudy weather, poor soil drainage, lack of air movement, late afternoon watering
• Severity increases with excessive N fertilization and on soils low in P and K
Smooth Crabgrass Control - Pendimethalin
0102030405060708090
100
Con
trol
(%
)
1.5 + 1.5 3
lbs. ai/acre
HeritageNone
* *
Rated 8/23/99
Smooth Crabgrass Control - Prodiamine
0102030405060708090
100
Con
trol
(%
)
0.65 + 0.5 1.15
lbs. ai/acre
HeritageNone
Rated 8/23/99
Smooth Crabgrass Control - Oxadiazon
0102030405060708090
100
Con
trol
(%
)
2.0 + 2.0 4
lbs. ai/acre
HeritageNone
Rated 8/23/99
Reseeding Restrictions
Balan 6 to 16 wks
Betasan 4 mos
Surflan 3 to 4 mos
XL 6 to 16 wks
Ronstar 4 mos
Pendulum 3 mos
Dimension 2.5 to 4 mos
Barricade 4 to 12 mos
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.• Relatively immobile in
the soil• Spring applications can
thin fall-seeded fescue
Tolerance of Fall-Seeded Tall Fescue to Spring-Applied Preemergence Herbicides
B. J. Johnson & T. R. Murphy
The University of Georgia
Methods
• Seeded ‘Ky 31’ in mid-Sept., -Oct. and
-Nov.
• Applied herbicides on Feb. 28
• 2 yr. study
• Recorded quality and density ratings following spring and early summer
Tolerance of Fall-Seeded Tall Fescue to Pre Herbicides
Herbicide Lbs. ai/acre
Balan 3.0
XL 2.0
Dimension 0.5
Surflan 2.0
Ronstar G 3.0
Pendimethalin 60DG 3.0
Results
• No herbicide reduced density of tall fescue seeded in mid-Sept. or mid-Oct.
• Pendimethalin, XL, Dimension, and Surflan reduced density 17 to 40% for fescue seeded in mid-Nov. in both yrs.
• In 1 of 2 yrs. Balan and Ronstar reduced density
Fall-Seeded Tall Fescue
• Related study showed that early-Nov. seeded tall fescue was tolerant to Feb. 1 + Apr. 1, Mar. 1 + May 1, or Apr. 1 + June 1 applications of Barricade at 0.5 + 0.5 lbs. ai/acre
– Prinster, SWSS Proc. 47:255.
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 required
• Uniform particle size is important
• Release characteristics of fertilizer product
• Control equivalent to sprayable and granular products
Preemergence Herbicides - Formulation Effects
Barricade lbs. ai/acreSmooth Crabgrass
Control (%)65WG 0.75 98
0.29G 0.75 91
0.5G 0.75 81
Yelverton, et al., 1996
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?
Timing Summer Annual Grass Control
• Late February to early March for crabgrass control
• Goosegrass two to four weeks later
• Early application (late January to early February) is OK due to slower herbicide decomposition during cool weather. (do only in well-established tall fescue)
Repeat Applications - Summer
• Space 8 to 10 wks apart
• Apply 1/2 X fb 1/2X
• May improve control of crabgrass and goosegrass
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
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
Avoiding Phytotoxicity• Read the label to make sure the herbicide is registered
for use on the turf• Apply the herbicide at the recommended rate and
determine application intervals• Test unfamiliar products and tank mixes on a small
scale