Turfgrass Weed Biology Turfgrass Weed Biology and Identificationand Identification

Tim R. MurphyTim R. Murphy

The University of GeorgiaThe University of Georgia

Why dowe control

weeds inturfgrasses?

WeedsWeeds

Compete with desirable plants for sunlight, Compete with desirable plants for sunlight, moisture and nutrientsmoisture and nutrients

Reduce yields or quality of harvested productReduce yields or quality of harvested product

Turfgrass WeedsTurfgrass Weeds

Reduce qualityReduce quality

- - leaf width, shape, color differencesleaf width, shape, color differences

Reduce densityReduce density- out-compete turfgrasses, can lead to - out-compete turfgrasses, can lead to

erosionerosion

Decrease aesthetic value or utility of the Decrease aesthetic value or utility of the turfgrass.turfgrass.

- difficult to mow, disrupt uniformity of playing - difficult to mow, disrupt uniformity of playing surfaces, safety considerations, attract insectssurfaces, safety considerations, attract insects

Control Control vs.vs. EradicationEradication

Control

Process of limiting a weed infestation to a level that is beneficial (economics, aesthetics, safety, etc.).

Eradication

Elimination of all plants and plant parts of weed species from an area.

Developing a Weed Management Developing a Weed Management ProgramProgram

Prevent weed introductionPrevent weed introductionProperly maintain turfgrassesProperly maintain turfgrassesIdentify weeds and learn life cycleIdentify weeds and learn life cycleInitiate control practicesInitiate control practices PreventivePreventive CulturalCultural MechanicalMechanical HerbicidesHerbicides

Why are weeds an annual problem?Why are weeds an annual problem?

Seed and vegetative structure dormancySeed and vegetative structure dormancy

Prolific seed producersProlific seed producers

Spread of seed (wind, birds, humans, etc.)Spread of seed (wind, birds, humans, etc.)

Turfgrass culture selects tolerant speciesTurfgrass culture selects tolerant species MonocultureMonoculture MowingMowing

Characteristics of Most WeedsCharacteristics of Most Weeds High reproductive outputHigh reproductive output

Some weeds produce 1000’s of seeds per plantSome weeds produce 1000’s of seeds per plant

Bimodal reproductionBimodal reproduction (more than one way to (more than one way to reproduce)reproduce)Dandelion – seeds and taproot fragmentsDandelion – seeds and taproot fragmentsVirginia buttonweed – seeds, stem fragments, Virginia buttonweed – seeds, stem fragments, rootsroots

Characteristics of Most WeedsCharacteristics of Most Weeds

Discontinuous germination or sproutingDiscontinuous germination or sprouting

Weed seeds can remain dormant in the soil for Weed seeds can remain dormant in the soil for many years and germinate sporadically. many years and germinate sporadically.

Crop and turf species are bred to NOT have Crop and turf species are bred to NOT have dormancy – hence all seeds germinate at the dormancy – hence all seeds germinate at the same time.same time.

Characteristics of Most WeedsCharacteristics of Most Weeds

Highly dispersibleHighly dispersibleWeeds must be able to colonize and invade.Weeds must be able to colonize and invade.

Ability to Withstand Environmental ExtremesAbility to Withstand Environmental Extremes

Ability to survive unexpected events. Ability to survive unexpected events.

Annual bluegrass and smooth crabgrass are Annual bluegrass and smooth crabgrass are found throughout the entire United States. found throughout the entire United States. (tremendous genetic diversity)(tremendous genetic diversity)

Characteristics of Most WeedsCharacteristics of Most Weeds

EarlinessEarliness

Many weeds germinate early and grow faster Many weeds germinate early and grow faster and taller than desired turf. Thus they are and taller than desired turf. Thus they are capturing resources (light, moisture, nutrients) capturing resources (light, moisture, nutrients) also needed by the turf. Various weed species also needed by the turf. Various weed species found at any time of the year.found at any time of the year.

Weed CompetitionWeed CompetitionCompetition will occur if there is one limiting Competition will occur if there is one limiting

resource needed by two or more plants.resource needed by two or more plants.

Weeds compete for the following resources.Weeds compete for the following resources.

LightLight

WaterWater

NutrientsNutrients

SpaceSpace

Weed CompetitionWeed Competition

Weeds efficiently compete because of:Weeds efficiently compete because of:

Early germinationEarly germination

Rapid seedling growthRapid seedling growth

Large leaf areaLarge leaf area

Extensive root systemsExtensive root systems

Tubers

Thickened portions of rhizomes or roots, serving for food storage and also for propagation (yellow nutsedge example)

Rhizomes

Underground stems that can emit roots from the lower side and leafy stems from the upper side (green kyllinga ex.)

Tubers and RhizomesTubers and Rhizomes

Weeds that produce tubers include purple Weeds that produce tubers include purple nutsedge, yellow nutsedge and Florida betony.nutsedge, yellow nutsedge and Florida betony.

Rhizomatous turfgrasses include bahiagrass, Rhizomatous turfgrasses include bahiagrass, bermudagrass, Kentucky bluegrass, tall fescue bermudagrass, Kentucky bluegrass, tall fescue and zoysiagrass.and zoysiagrass.

Rhizomatous weeds include dallisgrass, Rhizomatous weeds include dallisgrass, nimblewill and kyllinga species.nimblewill and kyllinga species.

Bulbs

Short, vertical, underground organs for food storage or reproduction on which specialized leaves prominently develop (wild garlic)

Weed Life CyclesWeed Life CyclesWeeds are classified as…Weeds are classified as…

Annuals (summer and winter)Annuals (summer and winter)

BiennialsBiennials

Perennials (warm-season and cool-Perennials (warm-season and cool-season)season)

Summer AnnualsSummer Annuals

Germinate in spring or early summerGerminate in spring or early summer Produce seed in the summerProduce seed in the summer Die with cold weather or frostDie with cold weather or frost

Live for only ONE growing season!Live for only ONE growing season!

Summer AnnualsSummer Annuals

GrassGrass BroadleafBroadleaf

Crabgrass speciesCrabgrass species Spotted spurgeSpotted spurge

Foxtail speciesFoxtail species Common lespedezaCommon lespedeza

GoosegrassGoosegrass Prostrate knotweedProstrate knotweed

SandburSandbur

Sedges:Sedges: annual sedge annual sedge

Southern crabgrass

Smooth crabgrass

GoosegrassGoosegrass

Common lespedeza

Prostrate knotweed

Prostrate spurge Milky sap

Chamberbitter, cannonball weed, gripeweed

Winter Annuals Winter Annuals

Germinate in fall or early winterGerminate in fall or early winter Over-winter (very slow growth) during coldest Over-winter (very slow growth) during coldest

monthsmonths Actively grow and produce seed in the springActively grow and produce seed in the spring Die in summer as temperatures riseDie in summer as temperatures rise

Live for only ONE growing season!Live for only ONE growing season!

Winter AnnualsWinter AnnualsGrassGrass BroadleafBroadleaf

Annual bluegrassAnnual bluegrass Chickweed speciesChickweed species

HenbitHenbit

Lawn burweedLawn burweed

Speedwell speciesSpeedwell species

KnawelKnawel

Hop cloverHop clover

Annual bluegrass Annual bluegrass Poa annua Poa annua L.L.

Boat shaped leaf tip

Common chickweed

Lawn burweed (spurweed)

henbithenbit

Henbit

Hairy bittercress

BiennialsBiennials

Germinate in fall or spring when conditions are Germinate in fall or spring when conditions are favorablefavorable

Usually found in rosette stage in 1st YrUsually found in rosette stage in 1st Yr

Produce seed and die in the 2nd growing seasonProduce seed and die in the 2nd growing season

Shiny cudweed

Purple cudweed

Warm-Season PerennialsWarm-Season Perennials

Germinate in spring or summerGerminate in spring or summer Can produce seed in the first summerCan produce seed in the first summer Can produce seed or reproduce by vegetative Can produce seed or reproduce by vegetative

means indefinitely (survive for many years due means indefinitely (survive for many years due to underground structures such as taproots, to underground structures such as taproots, rhizomes, tubers, bulbs and aboveground rhizomes, tubers, bulbs and aboveground structures such as stolons)structures such as stolons)

Warm-Season PerennialsWarm-Season Perennials

GrassGrass BroadleafBroadleaf

DallisgrassDallisgrass Virginia Virginia buttonweedbuttonweed

BahiagrassBahiagrass

SmutgrassSmutgrass

Sedge / kyllinga species:Sedge / kyllinga species: green and false-green green and false-green kyllinga, purple and yellow nutsedgekyllinga, purple and yellow nutsedge

DallisgrassDallisgrass

KyllingaSedge spp.

Virginia buttonweed

Purple Nutsedge – Purple Nutsedge – Cyperus rotundusCyperus rotundus

Introduced, native to Introduced, native to EurasiaEurasiaS. East U.S., CA and AZS. East U.S., CA and AZRanked world’s worst weedRanked world’s worst weedForms chains of Forms chains of interconnected tubersinterconnected tubersPrefers medium to fine-Prefers medium to fine-textured soilstextured soilsHighly adapted to Highly adapted to compacted soilscompacted soils

Yellow Nutsedge – Yellow Nutsedge – Cyperus esculentusCyperus esculentus

Native to North Native to North AmericaAmericaFound in all of U.S.Found in all of U.S.Ranked 16Ranked 16thth worst weed worst weed in worldin worldForms tubersForms tubersCommonly found in Commonly found in sandy soilssandy soilsThrives in non-Thrives in non-compacted soilscompacted soils

Cool-Season PerennialsCool-Season Perennials

Germinate in fall or winterGerminate in fall or winter Can produce seed in the first springCan produce seed in the first spring Can produce seed or reproduce by vegetative Can produce seed or reproduce by vegetative

means indefinitely (survive for many years due means indefinitely (survive for many years due to underground structures such as taproots, to underground structures such as taproots, rhizomes, tubers, bulbs and aboveground rhizomes, tubers, bulbs and aboveground structures such as stolons)structures such as stolons)

Cool-Season PerennialsCool-Season PerennialsGrassGrass BroadleafBroadleaf

Perennial ryegrassPerennial ryegrass Ground ivyGround ivy

Tall fescueTall fescue In. mock strawberryIn. mock strawberry

DandelionDandelion

Wild violetWild violet

Yellow woodsorrelYellow woodsorrel

White cloverWhite clover

Grass-Like:Grass-Like: Wild garlic Wild garlic

Perennial ryegrass clumps

Wild garlic

Wild garlicbulbs and bulblets

DandelionDandelion

Dandelion

Wild violet

Ground ivy

Identify the Weed ProblemIdentify the Weed ProblemREAD textbooks and periodicalsREAD textbooks and periodicals

Keep a diagnostic tool kit - hand lens, etc.Keep a diagnostic tool kit - hand lens, etc.

Know the life cycle of the pest (What temp. does a Know the life cycle of the pest (What temp. does a specific weed seed germinate?) specific weed seed germinate?)

Is the weed the cause or effect of the problem?Is the weed the cause or effect of the problem?

Confirm your diagnosisConfirm your diagnosis

ACES - ANR-616 UGA-CES

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* 214 weed species*575 color photos*Control info for each weed

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Turfgrass Web PagesTurfgrass Web Pages

www.georgiaturf.comwww.georgiaturf.com or .org or .org

437 photographs of 193 weeds437 photographs of 193 weeds

Control recommendationsControl recommendations

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Links to turfgrass organizations, GA Links to turfgrass organizations, GA automated weather networkautomated weather network