Weed Control in Turfgrass Systems Turfgrass IPM Workshop
November 11, 2011 Sarah J. Wilhelm Colorado State University Fort
Collins CO Slide 2 Causes of Turf Weed Problems Planting poor
quality seed or sod Weak, non-competitive turf Improper species or
cultivar selection Poor management practices Damaged by traffic,
stress, pests Slide 3 Use Weed-Free Seed! Slide 4 Creeping
bentgrass Poa trivialis Roughstalk bluegrass Slide 5 Adequately
fertilized turf Underfertilized turf Slide 6 Slide 7 Mowing Height
Affects Weed Seed Germination and Weed Vigor Slide 8 Necrotic Ring
Spot and Weeds Slide 9 Integrated Weed Management Program for Turf
l Prevent weed introduction l Properly maintain turfgrasses l
Identify weeds and learn life cycles l Utilize and evaluate control
practices Cultural Mechanical Biological Herbicide Use Slide 10
Good Cultural Practices Slide 11 Weeds Associated With Compacted
Soils l Annual bluegrass l Goosegrass l Knotweed l Prostrate Spurge
Slide 12 Weeds Associated With Moist or Poorly Drained Soils l
Annual bluegrass l Roughstalk bluegrass l Barnyardgrass l
Bentgrasses Slide 13 Weeds Associated With Infertile (Low Nitrogen)
Soils l Black medic l Plantain l White Clover Slide 14 Slide 15
Importance of Weed ID Learn life cycle and growth preferences Best
ways to manage with cultural practices Effective and LEGAL
herbicide use Slide 16 Warm-Season (C4) Species Most are annuals
Crabgrass, foxtails, goosegrass, sandbur, barnyardgrass Purslane,
spurge, knotweed, puncturevine Aggressive competitors with
cool-season (C-3) grasses during the summer months Slide 17
Cool-Season (C3) Species Bluegrasses, ryegrass, fescues,
bentgrasses are cool-season turf species Dandelion, thistle,
bindweed are cool-season broadleaf weeds Quackgrass, bromegrass,
annual bluegrass are perennial weedy grasses Grow best (and are
easiest to control) during spring and fall Slide 18 Weed ID Web
Sites North Carolina State University
http://www.turffiles.ncsu.edu/turfid/ Michigan State University
http://www.msuturfweeds.net/ Slide 19 Weed ID and Management Books
l Color Atlas of Turf Weeds. 2008. John Wiley and sons. l Weeds of
the West. 1991. The University of Wyoming. l Identifying Turf and
Weedy Grasses of the Northern United States.
http://pubsplus.uiuc.edu/C1393.html Slide 20 Classes of Turf Weed
Problems l Annual grassy weeds l Perennial grassy weeds l Sedges l
Broadleaf (dicot) weeds Slide 21 Grassy Weed Control is Difficult l
Infestation often goes unnoticed until it has become a major
problem l Selective control can be difficult n Species often
related sometimes same genus n Limited chemistry/number of
herbicides Slide 22 Annual Grassy Weeds Summer Annuals crabgrass
goosegrass foxtails barnyardgrass annual (?) bluegrass winter
annual bromes Slide 23 Preemergence Herbicides l benefin (Balan) l
benefin + trifluralin (Team) l bensulide (Betasan) l corn gluten
meal (Amaizing Lawn, WOW, many others) l dithiopyr (Dimension) l
isoxaben (Gallery) broadleaf weeds only l oxadiazon (Ronstar) l
pendimethalin (Pre-M, Pendulum, Scotts home products) l prodiamine
(Barricade) l siduron (Tupersan) for use at time of seeding l
mesotrione (Tenacity) both pre- and postemergence for annual
grasses Slide 24 Slide 25 Pre-emergence Herbicides DONT kill weeds
seeds DONT sterilize the soil DONT control weeds you can already
see (except for dithiopyr/Dimension) DONT harm trees and other
landscape plants whose roots are growing in the lawn CAN harm the
roots of desirable turf Slide 26 Annual Grass Control Ratings Slide
27 Corn Gluten Meal for Natural/Organic Weed Control Preemergence
herbicide activity ONLY Excellent N source (10% N) Cost is about
$1.00/pound Use rate of 20 pounds/1000 sq. ft. provides 2 lbs.
N/1000 Processed CGM provides moderate control of crabgrass and
other annual weeds Will not provide long-term control of perennial
weeds Raw corn meal is NOT effective Must use licensed sources of
GGM to apply legally! Slide 28 Causes of Unsatisfactory
Preemergence Herbicide Performance l Applied after weed emergence l
Rate applied was too low l Non-uniform application l Insufficient
(at application) rainfall or irrigation l Excessive rain
immediately after application l High rainfall year l Poor site
drainage l Drought l Excessive/prolonged summer heat l Clippings
collected before preemergent incorporated Slide 29 Preemergent
herbicide skip Slide 30 Preemergence Herbicide Efficacy l Loss of
activity may occur if not watered in within 7 to 10 days. l Losses
from photodecomposition and volatilization can be important,
especially with sprayable formulations l Avoid clipping collection
Slide 31 Single application at higher rate Split Preemergent
Herbicide Applications 2 nd Application Phytotoxicity level
Effective control level Time Herbicide Concentration 1 st
Application Slide 32 Perennial Weedy Grass Species Tall fescue
Quackgrass Bromegrass Bentgrass Zoysiagrass Bermudagrass Poa annua
Poa trivialis Slide 33 Sources of Perennial Grassy Weeds l
Contaminated seed or sod l Propagules present in soil at
establishment l Introduced in topsoil, organics, topdressing,
nursery materials (tree balls) l Encroachment from adjacent
landscape (neighbor lawns, golf courses, farmland, rangeland) l
Tracking by equipment, people, animals l Intentionally planted
Slide 34 Slide 35 Zoysiagrass patches in Kentucky bluegrass lawn
Slide 36 Managing Perennial Grassy Weeds Glyphosate (Roundup),
followed by reseeding or sodding Learn to tolerate the different
grass species There are new herbicides available for application by
lawn care professionals that can be used to SELECTIVELY remove tall
fescue, creeping bentgrass, rough bluegrass, quackgrass,
windmillgrass, nimblewill and bermudagrass from Kentucky bluegrass
lawns. PROPER IDENTIFICATION IS ESSENTIAL!!! Slide 37 Rough
bluegrass (Poa trivialis) Slide 38 Slide 39 Quackgrass (Elytrigia
repens) Coarse, blue-green leaves Aggressive rhizome former Rolled
vernation Early spring green-up Common ag and ditchbank weed Can be
selectively controlled in bluegrass turf with Certainty herbicide
(sulfosulfuron) Slide 40 Tenacity (mesotrione) l Has a novel mode
of action based on a naturally produced compound from the
bottlebrush plant (Callistemon citrinis) l Absorbed by leaves,
shoots, and roots and rapidly translocated in the xylem and phloem
of susceptible plants l Prevents carotenoid production in leaves,
leading to destruction of chlorophyll and cell membranes l Highly
active at low use rates as a pre- and post-emergence herbicide l
Provides selective broad-spectrum dicot and monocot weed control in
a number of turf species l Can use at or prior to seeding of
proposed labeled turfgrass species l Low toxicity to wildlife and
aquatic organisms and short persistence in the environment Slide 41
Mesotrione (Tenacity) for Bentgrass Control in Ryegrass and
Kentucky Bluegrass Syngenta Company l 2 applications 0.25 lb ai/A,
at 10-14 interval l 3 applications 0.17 lb ai/A, at 10-14 day
interval l 80-90% control at 15 weeks after treatment l Preemergent
and postemergent activity on crabgrass, some broadleaf weeds Slide
42 Grasses and Sedges Controlled by Tenacity Barnyardgrass (pre and
post) Creeping bentgrass (post) Crabgrass species (pre and post)
Foxtail, Yellow (pre and post) Goosegrass (pre and post) Nimblewill
(post) Yellow nutsedge (post) Windmillgrass (post) Slide 43 Turf
Species Labeled for Tenacity l Kentucky bluegrass (including Texas
x KBG hybrids) 0.16-0.25 lb. ai/a l Perennial ryegrass 0.16 lb.
ai/a l Tall fescue 0.16-0.25 lb. ai/a l Fine fescues (red,
Chewings, hard) 0.16 lb. ai/a Slide 44 Slide 45 Slide 46 Dicot Weed
Control Perennials Dandelion, clover, bindweed, thistle, plantain,
violet Annuals Spurge, puncturevine, oxalis, purslane Prevention
Proper establishment Ongoing maintenance Herbicides Gallery (good),
grass preemergents (fair) Many postemergent options Slide 47 Dicot
Weeds Can Be Difficult to Control Control is contingent upon
herbicide uptake and translocation Death of the weed may be slow
Mature weeds may not be controlled completely Slide 48 Postemergent
Herbicide Failure l Weeds curl and discolor, but dont die l Weeds
appear to have died, but come back l Reasons... Weed species Weed
age Weed health/vigor Slide 49 Seedlings are easier to control than
are mature weeds Slide 50 Drought-stressed weeds poor herbicide
uptake poor translocation difficult to kill Actively growing weeds
good herbicide uptake rapid translocation more easily killed Slide
51 Postemergent Broadleaf Herbicides l 2,4-D (many names, often
with other herbicides) l dicamba (Banvel) l MCPP, mecoprop (many
brands) l MCPA (many) l dichlorprop l triclopyr (Turflon Amine,
Turflon Ester) l clopyralid + triclopyr (Confront) l quinclorac
(Drive) l clopyralid (Lontrel) l chlorsulfuron (Corsair) l
metsulfuron methyl (Manor) l carfentrazone-ethyl (Quicksilver;
component of Speed Zone, Power Zone) l sulfentrazone (Dismiss)
(component of Surge and Q4) l mesotrione (Tenacity) Golf and sod
only; residential label expected late 2009 l sulfosulfuron
(Certainty) Slide 52 Postemergent Broadleaf Herbicides l 2,4-D
(many names, often with other herbicides) l dicamba (Banvel) l
MCPP, mecoprop (many brands) l MCPA (many) l dichlorprop l
triclopyr (Turflon Amine, Turflon Ester) l clopyralid + triclopyr
(Confront) l quinclorac (Drive) l clopyralid (Lontrel) l
chlorsulfuron (Corsair) l metsulfuron methyl (Manor) l
carfentrazone-ethyl (Quicksilver; component of Speed Zone, Power
Zone) l sulfentrazone (Dismiss) (component of Surge and Q4) l
sulfosulfuron (Certainty) l mesotrione (Tenacity) Golf courses and
sod only; residential label expected 2010 Slide 53 Dicot Weeds
Controlled by Tenacity Buttercup/Ranunculus (post) Chickweeds (pre
and post) Clover (pre and post) Dandelion (post) Oxalis (post)
Speedwell species (post) Canada thistle (post) Sowthistle (post)
Slide 54 Dismiss l Sulfentrazone l Safe on most cool- and
warm-season turf species l Excellent for sedge control l Good for
annual broadleaf weeds l Rapid activity l Shoot and root uptake
Slide 55 Surge l Sulfentrazone, with 2,4-D, MCPP, dicamba l
Cool-season grasses and buffalograss l Water-based amine, low odor
l For weed control when >90 F l Fast-acting (24-48 hrs) l
Photosynthetic inhibitor l Dandelion, clover, oxalis, spurge,
knotweed, plantain Slide 56 Q4 Plus l Quinclorac l Sulfentrazone l
2,4-D (amine salt) l Dicamba (amine salt) l Excellent cool-season
turf safety l Controls annual grassy weeds and long list of annual
and perennial broadleaf weeds Slide 57 Manor (metsulfuron methyl) l
For use on Kentucky bluegrass, fine fescue and buffalograss lawns l
Will damage perennial ryegrass l Low use rates: 0.125 to 0.5 oz.
product/acre l Controls ryegrass, thistle, spurge, oxalis, filaree,
yarrow, kochia, knotweed, dandelion, most legumes l Nufarm Turf and
Specialty http://www.turf.us.nufarm.com/ Slide 58 Control of Some
Common Broadleaf Weeds Slide 59 Black medic (Medicago lupulina) l
Healthy turf l Increase N fertility l Preemergent control Gallery l
Postemergent control MCPP, MCPA Drive Clopyralid products Slide 60
Yarrow (Achillea) l Healthy turf l Increase N fertility l
Preemergent control none l Postemergent control 3- and 4-way
products Clopyralid products VERY DIFFICULT WEED! Slide 61 Bindweed
(Convolvulus) l Healthy turf suppresses it l Increase N fertility l
Preemergent control none l Postemergent control 3- and 4-way
products Clopyralid products Drive, Q4 VERY good! Slide 62 A New
Weed Species Found in Colorado l Establishes quickly l Deep Rooted
l Resistant to conventional herbicides Slide 63 CSU Turf Program
Web Site http://csuturf.colostate.edu
