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Ralph Whitesides Pesticides And Ornamentals Handout

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  • 1. Using Pre-emergence Herbicides Effectively – Herbicide misuse Issues in the Landscape Ralph E. Whitesides Extension Weed Specialist Utah State University
  • 2. What is a pre-emergence herbicide?
    • Herbicide applied after crop is planted but before the weeds emerge
    • Does not work on established perennial weeds or crops
    • Requires rainfall or irrigation to activate the herbicide
  • 3.  
  • 4. Timing is Everything!
    • Herbicide on ground & activated prior to weed seed germination
    • Spray applications of pre-emergent herbicides applied in the rain
    • Irrigation required if no rainfall
  • 5.  
  • 6. Getting it Right!
    • Crabgrass in turf pre-emergence control indicators
    • Some use forsythia bloom
    • Too early – should be forsythia petal fall
    • Too early run the risk of “break through”
  • 7.  
  • 8.  
  • 9. Getting it Right! (continued)
    • Soil temperature – upper half inch of soil – early in day, not in sun, measure the site you intend to treat
    • Temperature above 50 °F three consecutive days make application!
    • Make split-applications if necessary
    • First part of split earlier than a single application – second treatment 7-8 weeks later
  • 10. Environmental Effects
    • Pre-emergence at right time & activated usually very good to excellent control
    • Must be threshold level of herbicide in soil to be effective
    • Abnormally high rainfall could dilute below threshold level – sandy soil is constant problem – consider split applications
  • 11. In Combination
    • Fertilizer carrier
    • Herbicide rate is fixed to fertilizer rate
    • Sprayed versus spreader delivered
    • Both do a good job if applied in time and activated
  • 12. Target Practice
    • Target weed – annual bluegrass
    • Winter annual – germinates in late summer/early fall
    • Apply mid-August if germination in September
    • Soil temperature – does not germinate until soil is consistently below 70 °F
    • Can’t control perennial annual bluegrass
  • 13. Gallery (isoxaben) Controls Perennial Broadleaves
    • Used for keeping dandelion and clover from re-invading turf
    • Necessary to control existing perennial first
  • 14. What could cause a pre-emergence herbicide to fail?
    • 1. You failed to read the label
    • 2. You disrupted the chemical barrier
    • 3. Your herbicide combination (or lack thereof) did not cover a broad weed spectrum
    • 4. You failed to incorporate the herbicide with irrigation
    • 5. You routinely over-watered your plants
  • 15.  
  • 16. What are 10 reasons that pre-emergence herbicides fail?
    • 1. You failed to read the label
    • 2. You disrupted the chemical barrier
    • 3. Your herbicide combination (or lack thereof) did not cover a broad weed spectrum
    • 4. You failed to incorporate the herbicide with irrigation
    • 5. You routinely over-watered your plants
  • 17.  
  • 18. What are 10 reasons that pre-emergence herbicides fail?
    • 1. You failed to read the label
    • 2. You disrupted the chemical barrier
    • 3. Your herbicide combination (or lack thereof) did not cover a broad weed spectrum
    • 4. You failed to incorporate the herbicide with irrigation
    • 5. You routinely over-watered your plants
  • 19.  
  • 20. What are 10 reasons that pre-emergence herbicides fail?
    • 1. You failed to read the label
    • 2. You disrupted the chemical barrier
    • 3. Your herbicide combination (or lack thereof) did not cover a broad weed spectrum
    • 4. You failed to incorporate the herbicide with irrigation
    • 5. You routinely over-watered your plants
  • 21.  
  • 22.  
  • 23. What are 10 reasons that pre-emergence herbicides fail?
    • 1. You failed to read the label
    • 2. You disrupted the chemical barrier
    • 3. Your herbicide combination (or lack thereof) did not cover a broad weed spectrum
    • 4. You failed to incorporate the herbicide with irrigation
    • 5. You routinely over-watered your plants
  • 24.  
  • 25.
    • 6. You tried to save a few pennies by using a lower herbicide rate
    • 7. You failed to use proper sanitation
    • 8. You topdressed fertilizers
    • 9. You did not calibrate your equipment
    • 10. You applied herbicides to soil/containers that already had weeds
  • 26.  
  • 27.
    • 6. You tried to save a few pennies by using a lower herbicide rate
    • 7. You failed to use proper sanitation
    • 8. You topdressed fertilizers
    • 9. You did not calibrate your equipment
    • 10. You applied herbicides to soil/containers that already had weeds
  • 28.  
  • 29.
    • 6. You tried to save a few pennies by using a lower herbicide rate
    • 7. You failed to use proper sanitation
    • 8. You topdressed fertilizers
    • 9. You did not calibrate your equipment
    • 10. You applied herbicides to soil/containers that already had weeds
  • 30.  
  • 31.
    • 6. You tried to save a few pennies by using a lower herbicide rate
    • 7. You failed to use proper sanitation
    • 8. You topdressed fertilizers
    • 9. You did not calibrate your equipment
    • 10. You applied herbicides to soil/containers that already had weeds
  • 32.  
  • 33.
    • 6. You tried to save a few pennies by using a lower herbicide rate
    • 7. You failed to use proper sanitation
    • 8. You topdressed fertilizers
    • 9. You did not calibrate your equipment
    • 10. You applied herbicides to soil/containers that already had weeds
  • 34.  
  • 35. Are there cases of herbicide misuse in the landscape?
    • 2009 example – provided with home owner approval
    • Homeowner had 5 London Plane (sycamore) trees
    • Fairly large caliper trees when planted
    • Now 12 years old
    • Trees 1, 3, and 5 were being encroached upon by trees 2 and 4
    • Decided to remove the trees on May 6, 2009
    • Cut the trees down with chain saw, removed the stumps and limbs
  • 36.  
  • 37. Bad Decisions
    • After trees were removed
    • Father-in-law says these will sucker and make a mess of the yard
    • We better treat the stumps!
    • I have just the stuff
    • Returns with container of Tordon 22K
    • Treats stumps with straight material using a brush
    • 13 days latter the call came to USU
  • 38.  
  • 39.  
  • 40.  
  • 41.
    • What did the yard look like in the beginning?
  • 42.  
  • 43.  
  • 44.  
  • 45.
    • What do you tell the homeowner now?
  • 46. Some Important Facts
    • Sycamore trees don’t sucker
    • Sycamore trees do root-graft
    • Tordon 22K is highly mobile in plants
    • Dow says the product likely moved into adjacent trees within 3-5 hours of original treatment
    • Separate the trees
    • Picloram can leak out of trees into soil
    • Remove soil and cut roots, remove stumps
  • 47.  
  • 48.  
  • 49.
    • What will happen to the trees that were not cut down?
  • 50.
    • Three months later
  • 51.  
  • 52.  
  • 53.  
  • 54.  
  • 55.  
  • 56.  
  • 57.
    • Seven months later
  • 58.  
  • 59.  
  • 60.  
  • 61.
    • When can I replant some trees?
  • 62.  
  • 63.  
  • 64. Picloram Persistence
    • Average field half-life is 90 days
    • Half-life range is 20-300 days
    • Dissipates more rapidly in warm moist conditions of the south
    • If half-life is 300 days it may take more than 3-5 years before it would be safe to replant deciduous trees
    • Highly leachable in some situations
  • 65.
    • How does this impact my neighbors?
  • 66.  
  • 67.  
  • 68.  
  • 69.
    • Read the Label
  • 70.
    • Follow label instructions
  • 71.
      • There is a reason why some pesticides are Restricted in Use – this example is one of them