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KNOTWEED, PROSTRATE
Knotweed, Prostrate
[Polygonum aviculare L.]
DESCRIPTION
Prostrate
knotweed is a low-growing summer annual or perennial which is very competitive
in compacted soils. It is often a problem along driveways, sidewalks, and beaten
paths. The slender stems radiate from a central taproot and produce a tough
mat-like growth. Leaves are dull, blue green, small, smooth and arranged
alternately along the stem. This weed germinates with the first warm
temperatures in the spring. Newly emerging seedlings are often mistaken for
grasses in very early stages of development.
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Characteristic
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Description
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Growth Season
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summer annual or perennial weed
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Growth Habit
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prostrate, spreading; mat-forming
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Leaflet Number
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one
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Leaf Margin
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smooth
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Leaf Hairs
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none
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Leaf/Leaflet Shape
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linear/oblong/oval/egg-shaped/elliptical
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Leaf Width
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1/2 - 1 inch
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Leaf Venation
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pinnate
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Leaf Arrangement
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alternate
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Root Type
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taproot
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Flower Color
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white to pinkish in color
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prostrate
knotweed nodes, leaves
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prostrate
knotweed
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Note: Still not
sure this is the right weed? The Turf
& Weed Identification Decision Aid may help. Check the TurfFiles glossary for definitions
of unfamiliar terms.
CULTURAL
CONTROL
Prostrate
knotweed is very competitive in infertile and compacted soils and often invades
turfgrasses along driveways, sidewalks, and beaten paths across lawns. Maintain
a dense, actively growing turf through proper mowing, fertilizing, and watering
practices. Mow at the proper height for your selected adapted turfgrass. Coring
and traffic control reduce compaction and encourage desirable turfgrass
competition. It is best to control this weed in late spring or early summer
because it is easier to control at this time and the turf will have a greater
chance of recovering the areas previously occupied by weeds.
CHEMICAL
CONTROL
Knotweed is controlled with
postemergence two, three and four way broadleaf herbicides applied in the
spring.
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Preemergence herbicides:
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Herbicide
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Tolerant Turfs (1)
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Average
Efficacy Rating(2)
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Range of Trial Efficacy Values, %
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Number of
Trials
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Products (3)
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atrazine*
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be, c, sa, z
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E
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0
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AAtrex 4L
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bensulide
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ba, bc, be, bk, c, f, r, sa, z
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G
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0
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Bensumec, Betasan
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isoxaben
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ba, bc, be, bk, c, f, r, sa, z
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G
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0
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Gallery 75
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oxadiazon*,**
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bc, be, bk, f, r, sa, z
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G
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0
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Quali-Pro Oxadiazon, Ronstar
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simazine
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be, c, sa, z
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G
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0
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Princep
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oryzalin
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ba, be, c, f, sa, z
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F
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0
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Quali-Pro Oryzalin, Surflan A.S.
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Postemergence herbicides:
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Herbicide
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Tolerant Turfs (1)
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Average
Efficacy Rating(2)
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Range of Trial Efficacy Values, %
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Number of
Trials
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Products (3)
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atrazine*
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be, c, sa, z
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E
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0
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AAtrex 4L
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dicamba
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ba, be, bk, f, r, z
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E
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0
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Banvel, Clarity, Vanquish
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glyphosate
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E
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0
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Glyphosate Original, Roundup, Touchdown Pro**
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metsulfuron
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be, sa, z
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E
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0
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Escort**, Manor
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fluroxypyr
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ba, bk, c, f, r, sa, z
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G
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0
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Spotlight
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metribuzin
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be
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G
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0
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Sencor 75 Turf
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2,4-D & triclopyr*
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bk, f, r
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F
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0
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Chaser
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Footnotes:
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(1)
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Turfgrass Codes:
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ba
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bahiagrass
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bc
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bentgrass, creeping
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be
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bermudagrass
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bk
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bluegrass, Kentucky
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c
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centipedegrass
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f
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fescue, tall
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r
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ryegrass, perennial
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sa
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St. Augustinegrass
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z
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zoysiagrass
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blank
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No turfgrass in the database is
completely tolerant. Check label to see if chemical can be used at a reduced
rate or during the dormant season on your turfgrass.
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(2)
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Efficacy Ratings:
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E
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excellent control (90 to 100%)
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G
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good control (80 to 90%)
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F
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fair control (70 to 80%)
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Efficacy ratings are based on
herbicide trials performed by weed scientists at North Carolina State University between 1997 and 2007. The number of trials included in the efficacy ratings
is displayed in the next-to-last column. The higher this number, the more
confidence can be placed in the efficacy values. Trials may have involved
sequential applications of one or more chemical. Details of individual trials
(herbicide rates, dates of application, environmental conditions at time of
application, etc) can be viewed on the TurfFiles web site, through the Turf Weed Management
Decision Aid.
Efficacy ratings for chemicals
lacking trial data are from “Pest
Management Strategic Plan for Turfgrass in the Southern United States,”
summary of a workshop for turf experts from multiple universities held in Griffin, GA in October, 2004 and sponsored by the Southern Region Integrated Pest
Management Center.
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(3)
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Recommendations of specific
chemicals are based upon information on the manufacturer's label and
performance in a limited number of trials. Because environmental conditions
and methods of application may vary widely, performance of the chemical will
not always conform to the safety and pest control standards indicated by
experimental data. The order in which brand names are given is not an
indication of a recommendation or criticism.
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Recommendations for the use of
agricultural chemicals are included in this publication as a convenience to
the reader. The use of brand names and any mention or listing of commercial
products or services does not imply endorsement by North Carolina State University or discrimination against similar products or services not mentioned. Other
brand names may be labeled for use on turfgrasses. Individuals who use agricultural
chemicals are responsible for ensuring that the intended use complies with
current regulations and conforms to the product label. Be sure to obtain
current information about usage regulations and examine a current product
label before applying any chemical. For assistance, contact your county's
Cooperative Extension agent.
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© North Carolina State University. This information sheet was prepared
by Fred Yelverton, Bridget R. Lassiter, Gail G. Wilkerson, Leon Warren, Travis Gannon, Jenifer J. Reynolds, and Gregory S. Buol. Department of Crop
Science, College of Agriculture & Life Sciences, North Carolina State
University. Prepared July 15, 2008. Available on-line at
www.turffiles.ncsu.edu. This publication was made possible through a grant
provided by the Center for Turfgrass Environmental Research & Education
(CENTERE) whose purpose is to support worthwhile projects that will benefit
both the private sector and the public, and protect the environment.
KEYWORDS FOUND IN THIS ARTICLE:
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