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Principles of Weed Control

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Weed Persistence. Nutrient Reserve is key issue. ... Usually not economical in perennial crops but may be required severe weed problems ... – PowerPoint PPT presentation

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Title: Principles of Weed Control


1
Principles of Weed Control
  • Pastures
  • Right of Ways
  • Lawns

2
What is a Weed?
  • Dallisgrass in Bermudagrass
  • Bermudagrass in Alfalfa
  • Alfalfa in flowerbeds
  • Basically, it is any plant that you do not want.

3
Know Your Weeds
  • 300 different plant species
  • in Northeast Texas

4
Only a Handful Economically Significant
  • Woolly Croton Milkweed
  • Pigweed Berryvine
  • Ragweed Thistles
  • Bitterweed Buttercup
  • Horsenettle Grassburs
  • Dogfennel Bahiagrass
  • Dallisgrass Crabgrass

5
Weed Identification
  • Plant type
  • Root growth patterns
  • bulb, tap, fiber, creeping
  • Life Cycle annual, biennial, perennial

6
Broadleaf plant structure
7
Grass Identification
  • Leaf shape is lancelike
  • Reproductive organ
  • Seedheads
  • Stolons/Rhizomes
  • Tillers
  • Growth habits
  • Upright
  • Prostrate

8
Reproductive Organs
  • Simple Produces only seeds with and without
    tillers (crabgrass)
  • Bulbous forms bulb and seed (false garlic)
  • Creeping produces seed, and growing reproductive
    organs such as stolons and rhizomes (bahiagrass)
  • Combination of the above (bulrush)

9
Weed Invasion Requirements
  • Stratification
  • cool period after seed fall
  • plant specific
  • Moisture
  • seed swell
  • Sunlight
  • Open sod

10
Weed Persistence
  • Nutrient Reserve is key issue.
  • The older the plant is and the more nutrient
    storage (reproductive) organs the plant
    possesses, the harder it is to control.

11
Keys to weed persistence
  • Seed crop size
  • Seed hardness
  • Nutrient Reserve
  • Size the bank account
  • Location underground is tough
  • Defenses (resistance to defoliation)

12
Battle Plan
  • Annuals
  • annual seed production required
  • kill flower, prevent seed formation
  • Early (pre-emergent) control is best
  • Perennials
  • Kill root, kills plant
  • Nutrient Reserve Depletion required
  • Control timing critical and weed specific

13
Weed Control Methods
  • Mechanical
  • Biological
  • Crop Rotation
  • Fire
  • Crop Competition
  • Prevention
  • Chemical

14
Mechanical Weed Control
  • Tillage
  • Plow
  • Cultivation
  • Burial
  • Mulch
  • Crop cover
  • Mowing
  • Mowing
  • Hay Harvest

15
Tillage
  • Plowing
  • primary form of establishment weed control
  • Cultivation
  • Works in rows, ineffective in broadcasts
  • Problems
  • Destroys root system of weed
  • Deep cultivation may hurt crop
  • Deep cultivation may bring up weed seeds
  • Expense (?)

16
Burial
  • Placing soil or mulch or other material over the
    reproductive organ
  • Effective with seed
  • Ineffective with plant parts (bulbs , rhizomes,
    etc.)
  • May destroy perennial crop
  • Living mulch possible
  • pastures and ROWs

17
Mowing
  • Effective on tall growing annual weeds (redroot
    pigweed)
  • Ineffective on short growing perennial weeds
    (dallisgrass)
  • or plants shorter than crop
  • Little benefit for current years grass program
  • Timing is critical

18
Biological
  • Lots of opinions
  • Method
  • Defoliation
  • Desiccation
  • Disease
  • Insect
  • Limited known control
  • Disease
  • Limited known control
  • Mammals
  • Possible

19
Biological
  • Effectiveness
  • Effective
  • plants of similar palatability and different
    growing patterns
  • Johnsongrass in bermudagrass
  • different livestock species
  • cattle/goats, horses/sheep
  • Ineffective
  • Plants of similar palatability and growth pattern
  • Toxic plants

20
Crop Rotation
  • Replacement of one crop with another
  • Allows use of cleanup herbicide program
  • Works best with annual crops
  • Usually not economical in perennial crops but may
    be required severe weed problems

21
Fire
  • Earliest recorded form of grass management
  • Multiple benefits (residue removal, control of
    spring weeds, increased infiltration)
  • Effective on young annual weeds
  • Ineffective on many perennial weeds
  • Fuel load is critical
  • 1500 lb. dm/ac.

22
Fire
  • Timing is critical
  • May damage crop plant
  • VERY RISKY, HIGH LIABILITY
  • Not recommended to most producers, land owners or
    anyone
  • Check with Law Enforcement and Fire Stations
    first.

23
Crop Competition
  • Long term solution
  • most economical
  • Requires compatible and useable crops
  • Growth patterns
  • Defoliate properly
  • Proper soil fertility levels required
  • K and other deficits

24
Effect of N Rate, herbicide and covercrop on weed
production
25
(No Transcript)
26
Bermudagrass Defoliation
  • Pastures
  • Regular defoliation
  • Intense defoliation in spring and early summer
  • stubble
  • Reduce intensity in late summer and allow
    nutrients to accumulate in roots
  • stubble 4
  • Lawns
  • Cut short (
  • Mow to match growth rate
  • 1 per week in early spring or late fall
  • 2-3 times weekly May through August (?)

27
Liebergs Law of Limits
28
Nutrient removed (lbs./ac.)by grazing and hay
29
Influence of Nitrogen and Potassium on Coastal
Bermudagrass Survival
30
Prevention
  • Vigilance required
  • Minimize soil disturbance
  • Keep adjacent areas, etc. mowed
  • Bring new items into weedy areas
  • New Seed
  • Out of region hay
  • Wildlife feeders
  • Keep grass crop vigorous and competitive

31
Chemical weed control
  • Pasture
  • Limited number of herbicides (10
    w/brush)
  • Price based on Income potential
  • Right of Way
  • Large number of herbicides (20)
  • Price compared to labor costs
  • Lawns
  • Extremely numerous herbicides (50)
  • Chemical cost is the price part of art?

32
Labeled Pasture HerbicidesBroadleafs
  • 2,4-D annual broadleaf
  • Dicamba Weedmaster
  • Picloram Grazon PD
  • Sulfanyl Urea Ally, Amber
  • specific weed tolerance and susceptibility
  • Rave Dicamba Amber

33
Labeled HerbicidesGrasses
  • Weedmaster Sprigging bermudagrass
  • Velpar smutgrass
  • Ally bahiagrass
  • Roundup new uses
  • Gramoxone afternoon applications

34
Basic Principles of Chemical Weed Control
  • Know your weeds
  • Choose the right herbicide
  • Match equipment with needs
  • Calibrate your sprayer
  • Spray at the proper time
  • Read and FOLLOW label instructions

35
Summary
  • Identify the weed and the crop
  • Timing is everything
  • Integrated Pest Management
  • Starve the weed, feed the crop
  • Mulch, Mow, Graze, etc. in the best manner
  • Seek multiple benefits
  • Chemical Weed Control
  • Spray annual weeds when young and actively
    growing
  • Spray perennial weeds at full leaf or fruit set
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