Weed Control in Crops Andrew Kniss Steve Miller Losses from

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Weed Control in Crops

• Andrew Kniss
• Steve Miller

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Losses from Weeds

• Exceed 13.5 billion annually
• Direct 7.5 billion
• Indirect 6 billion

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Direct Losses by Crop
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Direct Weed Losses by Crop
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Indirect Weed Losses

• Herbicides 2.3 billion
• Tillage 2.6 billion
• Other - 1.1 billion

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Yield Loss from Weeds

• Principle
• Given area of land can support a limited amount
  of dry matter

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Yield Loss
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Crop effects
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Weed effects
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Time effects
Yield reduction
Duration of competition
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Time effects
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Time effects
Bean yield reduction
Time of weed emergence
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Management

• Appropriate weed management practice determined
  by
• Management system
• Crop
• Economics
• Available technology

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Management

• The more restricted the number of operations in a
  management system, the more fully the practices
  that remain must be utilized
• In all management systems, the contribution of
  crop competition should always be fully exploited
• Allows us to manipulate the crop-weed interaction
  at a minimal cost

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Management

• Crop rotation
• Seeding rate
• Row spacing
• Fertilization
• Seeding date
• Competitive cultivars
• Smother crops

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Crop Rotation

• Mix up weed life cycles
• Allow rotation of herbicides

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Crop Rotation Effect on Weeds
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Row Spacing Dry beans

• Compared to 30 rows
• 22 rows reduced weed biomass by 70
• Bean yield remained the same
• 15 rows reduced weed biomass by 89
• Bean yield increased by 9

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Fertilization
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Seeding Date

• Early
• Late
• Fall
• Spring

• Cool season
• Warm Season
• Winter annuals
• Summer annuals

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Competitive cultivars

• Highest yield is not always the most competitive

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Competitive cultivars
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Herbicides

• Very important, but should never be sole
  management tactic
• Choice determined by many factors
• Crop rotation
• Persistence
• Weed spectrum
• Timing
• Resistance
• Others

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Herbicide Application Timing

• Preplant PPI
• Allows for incorporation or degradation prior to
  crop planting
• Preemergence PRE
• After crop is planted, prior to crop emergence
• Postemergence POST
• After crop and/or weeds have emerged
• Sometimes can be directed to avoid leaf contact

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Herbicide Application Timing

• PPI PRE require soil activity
• Must be absorbed by roots, hypocotyl, etc.
• Rarely activity on non-germinating seeds
• POST may or may not
• Usually not, leaf surface absorption usually but
  not always most important route of entry
• Contact herbicide NOT TRANSLOCATED!
• Only tissue contacted will die no soil activity

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Selected Herbicides
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2,4-D

• Most widely used herbicide in US WY
• Postemergence control of annual and perennial
  broadleaf plants
• Crops wheat, barley, corn, pasture

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2,4-D
No injury
Plant death
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2,4-D

• Formulations
• Acids
• Salts
• Esters
• Oil soluble amino

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2,4-D

• Acids
• Soluble in water
• Non-volatile
• Rarely used
• Unison Helena
• Not your daddys 2,4-D

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2,4-D

• Salts
• Inorganic Na, K
• Amines
• Soluble in water
• Non-volatile
• Most widely used

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2,4-D

• Esters Low or High volatile
• Volatility influenced by chain length
• Short high
• Long low
• Soluble in oil, not water
• Most effective form for penetration of thick
  cuticle

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2,4-D

• Oil soluble amino
• Soluble in oil
• Non-volatile
• Very expensive

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2,4-DB

• Butyrac
• Postemergence control of annual broadleaf plants
  in alfalfa
• Weeds lt3, alfalfa before flower
• Selectivity based on metabolism

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Dicamba Clarity (Banvel)

• PRE or POST control of broadleaf plants
• Crops wheat, oats, barley, corn, pasture
• Soil persistence 40 d / pint
• Corn PRE or cornlt36

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Dicamba
No injury
Plant death
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Atrazine - Aatrex

• PRE or POST
• POST requires COC
• Many annual broadleaf and grasses
• Crops corn fallow

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Atrazine - Aatrex

• Soil persistence
• Influenced by pH highly likely in WY
• Minimized by
• Band applications
• Herbicide combinations
• Deep plowing

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Chlorsulfuron - Glean

• PRE or POST
• Controls many broadleaf weeds, some grass
  suppression
• Crops wheat, barley, fallow
• Persistence very long soil residual
• gt36 month plant back to many broadleaf crops

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Bromoxynil - Buctril

• POST control of many annual broadleaf weeds
• Crops wheat, barley, oats, corn
• Timing 2 leaf to early boot stage
• Cereals have excellent tolerance

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EPTC - Eptam

• PPI Volatile
• Controls many annual grasses and some small
  seeded broadleaf weeds
• Sugarbeets, potatoes, dry beans, sunflowers,
  alfalfa
• Can be used in corn with safener
• EPTC safener Eradicane
• EPTC safener extender Eradicane Extra

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Desmedipham - Betanex

• POST control of annual broadleaf weeds in
  Sugarbeet
• Stage of application
• Full rate 4 leaf beets
• Micro-rate Cot to 4 leaf beets
• Need to add MSO
• Commercial mixes
• Betamix desmedipham phenmedipham
• Progress des phen ethofumesate

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S-metolochlor Dual Magnum

• PRE control of many annual grass and broadleaf
  weeds
• Crops corn, dry beans, sugarbeet

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Trifluralin - Treflan

• PPI volatile
• Many annual grass and broadleaf weeds
• Crops dry beans, sunflowers, alfalfa
• Persistence can carryover to damage sugarbeet

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Ethalfluralin - Sonalan

• PPI volatile
• Controls many annual grass and broadleaf weeds
• Crops dry beans, sunflowers
• Persistence less than Treflan

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Picloram - Tordon

• POST control of annual and perennial broadleaf
  plants
• Crops wheat, barley, oats, pasture
• Timing 3 to 5 leaf
• Soil persistence HIGH
• Broadleaf crops will be killed

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Picloram - Tordon
No injury
Plant death