Basics of Weed Control

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Basics of Weed Control Turf ID

• Jennifer Davidson
• The University of Georgia
• College of Agricultural and Environmental Sciences

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Attractive, Functional Landscape
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What is a Weed?

• Plant out of place
• Plants causing economic loss
• Non-native plant (Privet, Ligustrum spp.)
• Plants whose virtues have not been discovered

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Chinese Privet (Ligustrum sinense)
Kudza (Pueraria lobata)
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Weed Life Cycles
Annual Completes growth cycle in a single
growing season (crabgrass). Perennial A plant
that can persist more than two years, and
reproduce through roots or seeds
(clover). Biennial A plant that normally
requires two growing seasons to complete its life
cycle, flowering and fruiting in its second year
(wild carrot).
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Seed Germination Factors

• Temperature
• Water

• Oxygen
• Light
• Scarification (physical removal of the seed coat)

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Weed Seed Production
Seed / Plant Pigweed
gt200,000 Lambsquarters
gt30,000 Crabgrass
53,000 Annual Bluegrass 2,000
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Weeds can be a problem 12 months a year!
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Summer annual grasses
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Southern crabgrass
Smooth crabgrass
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Goosegrass
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Winter annuals
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Annual bluegrass
Boat shaped leaf tip
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Common chickweed
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henbit
Henbit
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Hairy bittercress
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Summer annual broadleaf weeds
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Prostrate spurge
Milky sap
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Perennial broadleaf weeds
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Dandelion
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Wild violet
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Pennywort or Dollarweed
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Perennial grassy weeds
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Wild garlic
bulbs and bulblets
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Purple and Yellow Nutsedge
Yellow nutsedge flower
Purple nutsedge flower

• Leaf tips differ

Purple nutsedge rhizome tuber system
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Dallisgrass
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Weed Management Strategy

• Identify weed, life cycle, habitat
• Integrated Pest Management
• Preventive
• Physical
• Cultural
• Biological
• Chemical

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Preventive Methods

• Weed-free seed and plant material
• Screened and sterilized topsoil and soil
  amendments
• Keep equipment clean

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Physical Removal and Barriers

• Hoeing and hand removal
• Mowing
• Cultivation
• Mulches and landscape fabrics

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Hand Pulling and Hoeing

• Good control method for small weeds
• Generally easier to control annuals

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Mowing

• Useful in turf and pastures
• Mowing reduces seed production of weeds if done
  before flowering.

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Cultivation
Advantages Controls most weeds quickly and
easily

• Disadvantages Can be expensive, delayed by
  weather, and may prune crop roots

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Repeat cultivation to control each flush of
weeds.
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Cultural Methods

• Adapted plants
• Fertility and pH
• Water management
• Insect and disease control

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Biological Methods

• Living organisms for weed control

• Insect (thistle weevil)
• Grazing animals (Geese)
• Fish (Grass carp)

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Chemical Methods
Herbicide - chemical that is used to control,
suppress or kill weeds.
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Herbicide Classification
Preemergence Applied before weed seed
germination (trifluralin). Generally no control
of emerged weeds. Postemergence Applied after
weed emergence. Generally no control of
unemerged weeds.
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Herbicide Classification
Contact Causes localized plant tissue injury.
Does not readily move through the plant
(glufosinate) Systemic Readily moves through
the plant tissue (glyphosate)
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Herbicide Classification
Selective Kills some plant species, but does
not damage others (2,4-D) Nonselective
Generally kills all plant species (glyphosate)
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Preemergence Herbicide Application Dates
Fall - Sept 1 Oct 1, N.GA - Oct 1 Nov 1,
S.GA Spring - Mar 1 Apr 1, N.GA - Feb 15 -
Mar 15, S.GA
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AdvantagesPostemergence Herbicides

• Flexible application time
• Spot treatment
• Small containers
• Fits well into IPM programs

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PostemergenceHerbicide Precautions

• Avoid windy days (spray drift)
• Do not apply dicamba mixtures over the root zone
  of ornamental trees and shrubs
• Read the label

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Before You Use Herbicide

1. Identify weed.
2. Read and UNDERSTAND label .
3. Follow directions carefully.
4. Use only recommended amount!
5. Maintain and calibrate equipment.
6. Do not use on desirable plants not listed on
   label.

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Turfgrass Herbicides
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Preemergent Turfgrass Herbicides

• Annual grass control in all turfgrasses
• Balan (benefin)
• Surflan (oryzalin)
• XL (benefin oryzalin)
• Team Pro (benefin trifluralin)
• Halts (pendimethalin)
• Dimension (dithiopyr)

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Postemergent Turfgrass Herbicides
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2,4-D Mixtures

• Does not control weedy grasses
• Good - dandelion, plantains, wild garlic
• Poor to fair common chickweed, henbit
• Use on all turfgrasses except St. Augustine
• Example Weed-B-Gon

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MSMA DSMA CMA

• Postemergence control of weedy grasses
• Use in tall fescue, zoysia, bermuda
• Initially discolor tolerant turfgrass species
• Avoid application above 90o F
• Do not use on centipede and St. Augustine
• Example Ortho Crabgrass Killer Formula II

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Sethoxydim

• Controls crabgrass, goosegrass, and sandbur
• Suppresses bahiagrass
• Use only on centipedegrass
• Example Vantage

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Atrazine

• Can be used on Centipede, St. Augustine, Zoysia
• Dormant bermudagrass
• Cool-season grasses and bahiagrass are not
  tolerant
• Comes in both sprayable and granular formulations
• Depending on the weed, atrazine has both pre and
  post emergence activity

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Turfgrass Fertilizer/Herbicide Combinations

• Fertilizers can be combined with either pre- or
  postemergence herbicides.
• Created so you dont have to make separate
  applications of fertilizers and herbicides.
• Products available from many manufactures selling
  nearly identical products.

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Equipment
Hand pump Sprayer
Handheld rotary spreader
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Equipment
Drop spreader
Broadcast spreader
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Calibration

• Hand held granular spreaders
• Know the size of the area to be treated
• Weight out granular herbicide needed for that
  area
• Uniformly apply the pre-weighted granular
  herbicide to the designated area

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Calibration

• Push type drop and broadcast spreaders
• Many companies sell spreaders to go along with
  there granular herbicides (i.e. Scotts, Lesco,
  etc.).
• There granular herbicide products will have the
  appropriate spreader setting listed on the bag.

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Calibration and Application
Pump type sprayers

• Measure the area to be treated.
• Using the herbicide label, determine the amount
  of herbicide needed.
• Measure out herbicide.
• Mix water and herbicide concentrate.
• Pressurize sprayer, and uniformly apply herbicide
  solution to the are.

Hand pump sprayer
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Weed management program

1. Diagnose problem
2. Evaluate methods
3. Select method
4. Initiate program

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Always read and follow the herbicide label!
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Warm-season Turfgrasses

• Bermudagrass
• Centipedegrass
• Zoysiagrass
• Seashore Paspalum
• St Augustinegrass
• Bahiagrass

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Bermudagrass Cynodon dactylon

• Vegetative
• Tifway 419
• most used hybrid
• Tifway II
• Frost Tolerant
• TifSport
• New Cold Hardy Hybrid
• Non-preference to mole crickets

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Bermudagrass

• Vegetative-types
• Tifgreen (Tifton 328)
• Fine Textured
• Low growing
• Tifton 10
• Coarse Textured
• Dark bluish-green
• Low maintenance areas
• Midlawn
• Transition zone
• Cold tolerance

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Bermudagrass

• Seeded types
• Common
• Coarse Textured
• Low maintenance areas
• Improved
• Finer textured
• Low maintenance areas

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ZoysiagrassZoysia spp.

• Vegetative
• Meyer
• Slow growing
• Emerald
• Fine texture
• El Toro
• Faster establishment
• Better drought tolerance

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Zoysiagrass

• Seeded
• J-36
• Coarse texture
• Zenith
• Med. To coarse
• Zenith II
• Dark green
• Med. texture

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CentipedegrassEremochloa ophiuroides

• Medium Textured
• Low Slow Growing
• Stolons Seed
• Intermediate Shade Tolerance
• Longer to Establish
• Centipede Decline

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Centipedegrass

• Vegetative Seeded
• Common
• Coarse texture
• Minimum maintenance
• TifBlair
• Cold Hardy
• Low pH (4.2)

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St. AugustinegrassStenotaphrum secundatum

• Blue-green Color
• Deep, Dense Turf
• Stolons
• Shade Tolerant
• Winter Injury
• Chinch Bugs

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St. Augustinegrass

• Varieties
• Floratam
• Coarsest Texture
• Chinch Bugs SADV Resistance
• Gray Leaf Spot

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St. Augustinegrass

• Varieties
• Bitter Blue
• Best Shade Tolerance
• Chinch Bugs SADV
• Floratine
• Finest Leaf Texture
• Chinch Bugs SADV

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Mowing Practices

• 1/3 rule
• Gradually change height
• Recycle (leave or compost)
• Change directions
• Keep mower in good working order

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Rotary Mowers

• Disadvantages
• Low quality of cut
• No low heights
• 1-inch minimum
• No striping

• Advantages
• Fewer man-hours
• Lower maintenance
• Grasscycling

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Reel Mowers

• Disadvantages
• Higher maintenance
• More man-hours

• Reel Mowers
• High quality of cut
• Lower heights
• Minimal scalping
• Striping

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Proper Mowing Height
Species Mower Height (in) Frequency (days)
Bermuda
Common Rotary or Reel 1 to 2 5 to 7
Hybrid Rotary or Reel 0.5 to 1.5 3 to 4
Centipede Either 1 to 2 5 to 10
St. Augustine Rotary 2 to 3 5 to 7
Zoysia Reel 0.5 to 2 3 to 7

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Irrigation

• Water application based on soil or plant
  moisture status is more efficient than applying
  water based on a set schedule

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So--When should you irrigate?

• 1st signs of water stress
• Visual Symptoms
• Dull bluish green color
• Footprints remain
• Leaf blades roll

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When is the best time to irrigate?

• After the dew falls and before it dries-
• Water losses lowest (Less wind and lower temps)
• Does not promote disease

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How Much to Irrigate?

• Wet 6 to 8 inch depth
• clay soils (1 to 1¾ inches per week)
• sandy soils (½ inch, 3 times a week)

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Proper Irrigation

• Cultural Practices
• Only wets the turfgrass rootzone
• Does not saturate the soil
• Does not allow water to run off

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Questions?
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