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Weed Management
in the Landscape
Calvin Odero
Everglades REC
Belle Glade
Outline
• Weeds
– Weed classification, ID diagnostics
• Weeds and landscapes
• Lawns and turf
– New
– Established
• Landscape ornamentals
What is a weed?
• Common definitions:
– Plant growing where it is not wanted
– Plant out of place
– Plant that is a nuisance
– Plant whose virtue has not been discovered
– Plant that is objectionable or interferes with
the activities or welfare of man (WSSA)
Weeds and landscapes
• Weeds are usually the most visible
of landscape pests
• Weeds are of concern principally
because
− Compete with desirable plants
− Destruct the appearance and function
of landscapes
• Aesthetically unappealing
• Weeds can harbor insect and
disease pests
• May pose a health hazard to
humans
– poison ivy, common ragweed
Weeds and landscapes
• Other harmful aspects of weeds
– Increase the cost of site preparation
– Increase the cost of maintenance
– Increase the cost of protection
Weed classification
• Phylogenetic relationships
– Ancestry, ancestral similarities
• Habitat
– Cropland, rangeland, aquatic,
environmental, parasitic,
landscape
• Type of plant
– Broadleaf, grass, sedge
• Life history
– Annual, biannual, perennial
Weed identification
• Proper identification and understanding of
growth habits of weeds are important
– Determine weed vulnerabilities
– Important step towards control
• Identification of the best management
strategies
– Selection of effective control method,
ex. herbicides , application timings
Grass weed diagnostics
• One cotyledon or seed-leaf
• Leaf blades are long, narrow,
alternate with parallel veins
• Leaf sheath encircles the stem
• Junction of leaf blade with sheath
is the collar
• Ligule (projection at base of leaf
blade)
• Auricles (claw-like projections at
the leaf collar that partially encircle
the stem)
Smooth crabgrass (Digitaria ischaemum)
• Very wide first leaf
• Initial clumping
growth progressing to
prostrate, tillering
• Visible membranous
ligule
• Hairless
• Inflorescence
– 2-6 fingerlike branches
Southern crabgrass (Digitaria ciliaris)
• Seedling
– Hairy leaves, sheath,
and collar
• Upper leaves
occasionally hairy on
upper surface only
• Membranous ligule
• Infloresence
– 2-9 fingerlike branches
Bermudagrass (Cynodon dactylon)
• Easy to identify
–
–
–
–
Small leaves
Rhizomes and stolons
Mat forming
Ligule fringe of short
hairs (hard to see)
• Produces seed and
spreads vegetatively
Goosegrass (Eleusine indica)
• Low growing
– Very white, stems
flattened
– Looks like it has been
stepped on
– Ligule uneven,
membranous
Grass-like plants
Spreading dayflower
Doveweed
Broadleaf weed diagnostics
• Two cotyledons or seed
leaves (dicots)
• Leaves have netlike veins
(wider than grasses)
• True leaves develop above
cotyledons
• Leaves have a petiole (leaf
stalk) or may be sessile
(without a petiole)
• Leaves alternate or
opposite
• Stem erect, viny or twining,
prostrate
Broadleaf weeds
Persian speedwell
Spiny sowthistle
Brambles
Annual sowthistle
Common groundsel
Hairy bittercress
Smooth bedstraw
Hyssop spurge
Carolina geranium
Garden spurge
Prostrate spurge
Yellow woodsorrel
Sedge diagnostics
•
•
•
•
3-angled stems
Leaves arranged in threes
Long grass-like leaves
Propagation primarily by
tubers
Sedges
Yellow nutsedge
• A - sharp or needle like tip
• Tubers produced at end of
rhizomes
Purple nutsedge
• B - boat shaped tip
• Tubers produced along the
length of rhizomes
A
Yellow nutsedge
B
Purple nutsedge
Weed identification
• Weed ID manuals feature
– Small & mature weeds, flowers, fruit
characteristics
– http://erec.ifas.ufl.edu/weeds/index.html
Weeds and landscapes
• Control can be difficult due
to complexity of many
plantings
− More than one species
planted
− Mix of annual and perennial
ornamentals
• Requires a variety of weed
management options
Weeds and landscapes
• To plan for an existing
planting or after an
installation is in place,
consider
− Type of plants present
• Woody plants can tolerate
herbicides that would injure an
herbaceous plant
− Weeds present and their
lifecycles
– Public concerns
• Use of herbicides
– Effect of herbicide runoff on
water quality
Weeds and landscapes
• Because of the many variables,
weeds in landscape plantings
are usually controlled by
− Combination of nonchemical and
chemical methods
• A balanced weed management
plan requires an integrated
approach
Weeds and landscapes
• Integrated approach would include
– Prevention
– Sanitation
– Hand weeding
– Mulching
– Mowing
– Cultivation
– Use of herbicides
Lawns and turf
• Turf areas include home lawns,
commercial lawns, golf courses,
parks, recreational areas,
roadsides
• Management practices produce
a strong and vigorous turf
– Choice of adapted lawn grass
species, proper grading and seed
bed preparation, fertilization,
mowing, watering, pest control
New lawns
• Before planting
– Cultivation
– Herbicides with no residual toxicity to the turf to
be seeded or sodded later
• Glyphosate, glufosinate
• After planting
– Mowing
– Herbicides
• Low rates of growth regulator herbicides to avoid injury
(1/4 – 1/2X rates)
• Rates can gradually increase as grass becomes
established
Established lawns
• Grasses have developed extensive root
system, well tillered, rhizome system
(runner) well developed
• Properly manage turf to produce a dense,
healthy, actively growing stand
– Good management
• Weeds can be controlled by hand pulling or cutting
– Symptom of poor management
• Large weed populations
Established lawns
• Proper management
– Mowing height, mowing frequency, adapted
species, fertilization, irrigation, thatch
management
• If weeds become a problem, there are
many herbicides that may be used
• Established turf tolerates herbicides much
better than new planting
Established lawns: herbicides
• Soil-active (PRE) and foliar-active (POST)
• PRE – applied 2-3 weeks before weed
seed germination
– Require immediate overhead irrigation/rainfall
• POST – emerged weeds
– Effective if weeds have active growth and not
stressed
– Check herbicide rainfast before application
Established lawns: herbicides
• Tolerance of turfgrass species differ
• Many commercial formulations contain
two- and three-way mixes
– Provide a wide spectrum of weeds
• Lawn fertilizers are formulated with
broadleaf and grass herbicides
Grass control
• POST control in tolerant species through
single/repeat applications of organic arsenicals
– MSMA (Fertilome, Dallisgrass Killer)
– 2-4 applications at 7-10 days required for complete control
– Rate, number of applications increase as weeds mature
• POST control of grassy weeds in centipedegrass
– Sethoxydim (Vantage)
– Atrazine-containing materials (Scotts Bonus Type S, Hi-Yield)
• Provide good control of young grassy weeds with the added benefit
of controlling many young broadleaf weeds
Broadleaf control
• Controlled with
– Phenoxy (2, 4-D, MCPA, mecoprop)
– Benzoic acid (dicamba)
• Selective, systemic, foliar-applied herbicides
• Few broadleaf weeds, especially perennials, are controlled with just
one of these herbicides
• These materials are commonly found in three-way
herbicide mixtures
–
–
–
–
Trimec
Ortho's Weed-B-Gon
Spectracide Weed Stop
Repeat applications at 10-14 days apart necessary for
satisfactory weed control
Sedges
• Thrive in soils that remain wet
for extended periods of time
– Poor drainage
– Excessive irrigation
• The first step in nutsedge
control
– No overirrigation
– Provide surface and subsurface
drainage
Sedge control
• Repeat applications of the organic arsenicals (MSMA)
– Effective but treatments are slow to kill the weeds, repeat
applications are necessary, will result in extensive damage to
certain turf species
• Selective control
– Bentazon (Basagran T/O, Hi-Yield Basagran)
• Contact, complete coverage necessary for better bentazon efficacy
• Regrowth will normally occur from roots and tubers
• Repeat applications necessary
– Halosulfuron (Manage)
– Imazaquin (Image)
• Repeat applications, possibly over several years, required to control all
the underground reproductive parts or purple nutsedge.
Landscape ornamentals
• Balanced weed management
program requires an
integrated approach
– Prevention, sanitation, hand
weeding, mulching, cultivation,
use of herbicides
• Herbicides may have a lesser
role with a balanced
approach to weed
management
Prevention and sanitation
• Establishing plants in a weed-free
environment is critical to long-term success
• Exclude weed introduction
– Contaminated potting soil
– Contaminated stock plants
•
•
•
•
Never allow weed seed production
Scout to identify infestations
Removal of containers with perennial weeds
Disposal of pulled weed biomass
Cultivation
• Manual
– Tedious, expensive, but occasionally necessary
• Mechanical methods
–
–
–
–
Rototilling
Disking
Plowing
Hoeing
• Care must be employed to avoid physical
damage to valuable plants during weed
removal
Mulching
• Very effective method of weed
control
• Mulching the soil surface
– Reduces light necessary for
germination
– Presents a physical barrier to
emergence
– Moisture retention
– Soil stabilization
– Enhanced aesthetics
– Reduction in the need for
herbicides
Mulching
• Natural organic
– Composted yard wastes or animal wastes, grain
straw, peat moss, pine straw
– Wood chips, hardwood bark, softwood bark
– Placed 2-3 inches or greater depths
• Natural inorganic
– Sand, pebbles, stones, shale
– Require plastic mulch on soil surface beneath them or
use of herbicide
• Synthetic materials
– Polyethylene or woven synthetic fabric
– Prevent weed seeds from germinating
Use of herbicides
• PRE and POST
• Wide variety of tolerance to herbicides
• Non-selective herbicides ideal for brick
walks, along landscape bed borders,
under woody ornamentals
• ALWAYS READ THE HERBICIDE LABEL
– IT IS THE LAW
Contact Information
Telephone: 561-993-1509
Email: [email protected]
References
• Weed management in landscapes
http://www.ipm.ucdavis.edu/PDF/PEST
NOTES/pnweedmanagement.pdf
• Weed management in landscapes
http://cecalaveras.ucdavis.edu/weed.htm
• Weed control in gardens and landscapes
http://www.hort.purdue.edu/ext/ho-217.pdf
• Weed Control Options in Landscape Beds and
Groundcovers
http://www.ctahr.hawaii.edu/oc/freepubs/pdf/L12.pdf