Snmek 1

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Efficacy and selectivity of pre-emergence
herbicides in sunflower as influenced by soil
water conditions
Miroslav Jursík Jirí Andr Veronika Venclová Josef
Soukup E-mail jursik_at_af.czu.cz
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Typical sunflower weeds in the Czech Republic
Echinochloa crus-galli
Polygonum lapathifolium
Chenopodium album
Amaranthus retroflexus
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Locally occurring sunflower weeds in the Czech
Republic
Solanum nigrum
Abutilon Theophrasti
Mercurialis annua
Datura stramonium
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Weed control in sunflower in Czech Republic

• 90 of sunflower area is treated by
  pre-emergence soil herbicides
• sunflower is very sensitive to many herbicides
  metabolic type of selectivity is usually low
• intensive precipitation after herbicide
  application (especially on sandy soil) may cause
  vertical movement of herbicide into the zone with
  germinating seeds of sunflower and damage them
  (phytotoxicity)

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Pre-emergence weed control in sunflower in the
Czech Republic

• widely used tank-mix combinations
• of herbicides

• linuron
• prosulfocarb
• oxyfluorfen
• pendimethalin
• flurochloridone
• bifenox

• acetochlor
• alachlor
• dimethenamid
• metolachlor

grass weeds
dicot weeds
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Material and methodsTrial layout

• tested herbicides

Half of each plot was irrigated by simulation of
30 mm precipitations (2-3 weeks after herbicide
application)
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Material and methods

• experimental years 2008 and 2009
• soil characteristic chernozem, clay content 46
  , soil pH (KCl) 7.5, sorption capacity of soil
  209 mmol(), 87 ppm P, 203 ppm K, 197 ppm Mg,
  8073 ppm Ca
• occurring weeds Echinochloa crus-galli,
  Amaranthus retroflexus, Chenopodium album and
  Mercurialis annua

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Materials and methods
Soil moisture conditions
dry condition natural precipitation 25 mm
within 4 WAT wet condition intensive natural
precipitation (65 mm within 4 WAT) simulated
rainfall (natural precipitation 25 mm within 4
WAT 30 mm irrigation)
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Efficacy of tested herbicides on Amaranthus
retroflexus under different rainfall conditions
low efficacy in dry condition
low efficacy in dry condition
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Efficacy of tested herbicides on Chenopodium
album under different rainfall conditions
efficacy was not influenced by rainfall
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Efficacy of tested herbicides on Echinochloa
crus-galli under different rainfall conditions
efficacy was not influenced by rainfall
efficacy was not influenced by rainfall
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Efficacy of tested herbicides on Mercurialis
annua in different dry condition
efficacy was not influenced by soil moisture
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Selectivity of tested herbicides to sunflower in
different dry condition4 week after application
no phytotoxicity in all tested rainfall conditions
phytotoxicity influenced by size of rain drops
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Conclusions
acetochlor

• excellent and long-term residual efficacy on E.
  crus-galli and A. retroflexus
• efficacy was not affected by rainfall

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Conclusions
acetochlor
Chenopodium album
Mercurialis annua
wet conditions
dry conditions
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Conclusions
acetochlor

• excellent and long-term residual efficacy to E.
  crus-galli and A. retroflexus
• efficacy was not affected by soil moisture
• slow metabolism by sunflower - risk if used on
  sandy soil
• sunflower injury is often hidden and cause a grow
  retardation

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Conclusions
oxyfluorfen

• excellent efficacy on A. retroflexus and very
  good efficacy on M. annua not very influenced
  by rainfall

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Conclusions
oxyfluorfen
Chenopodium album
E. crus-galli
wet conditions
dry conditions
only in
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Conclusions
oxyfluorfen

• excellent efficacy on A. retroflexus and very
  good efficacy on M. annua not very influenced
  by rainfall conditions
• short residual activity
• slow metabolism by sunflower phytotoxicity was
  caused by rain drops which reflected from soil
  surface necrosis and deformation of leaves

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Conclusions
linuron

• good efficacy on all tested weeds, but only in
  wet conditions
• very low efficacy in dry conditions

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Conclusion
linuron
wet condition
dry condition
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Conclusion
linuron

• good efficacy on all tested weeds, but only in
  wet conditions
• low efficacy in dry conditions
• relative short residual activity (up to 2 months
  after application) fast development of
  sunflower leaf coverage is necessary
• high selectivity to sunflower possibility of
  use on sandy soils

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Conclusion
flurochloridone

• Lower selectivity to sunflower risk if used on
  sandy soils
• phytotoxicity symptom on sunflower is bleaching
• excellent efficacy on all tested weeds, but only
  in wet conditions
• reduced efficacy mainly on E. crus-galli and M.
  annua in dry conditions
• long-term residual activity

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Conclusion
flurochloridone
wet conditions
dry conditions
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Conclusions
prosulfocarb

• excellent efficacy on all tested weeds, but only
  in wet conditions
• in dry soil conditions, good efficacy was found
  only on A. retroflexus

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Conclusion
prosulfocarb
wet condition
dry condition
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Conclusions
prosulfocarb

• excellent efficacy on all tested weeds, but only
  in wet conditions
• in dry conditions good efficacy only on A.
  retroflexus was found
• relative short residual activity
• high selectivity to sunflower possibility of
  use on sandy soils

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Conclusions
pendimethalin

• excellent and long-term efficacy on C. album in
  all tested wet conditions
• for other assessed weeds - short residual
  activity and efficacy is partially influenced by
  soil water conditions

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Conclusion
pendimethalin
wet conditions
dry conditions
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Conclusion
pendimethalin

• excellent and long-term efficacy on C. album in
  all tested conditions
• for other tested weeds - short residual activity
  and efficacy is partially influenced by soil
  watter conditions
• breaking and lodging of stems may occurr as a
  result of callus creation on stem base

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