Miroslav Jursík Jiří Andr Veronika Venclová Josef Soukup E-mail: jursik@af.czu.cz

1. Efficacy and selectivity of pre-emergence herbicides in sunflower as influenced by soil water conditions Miroslav Jursík Jiří Andr Veronika Venclová Josef Soukup E-mail: jursik@af.czu.cz

2. Typical sunflower weeds in theCzech Republic Echinochloa crus-galli Polygonum lapathifolium Chenopodium album Amaranthus retroflexus

3. Locally occurring sunflower weeds in theCzech Republic Solanum nigrum Abutilon Theophrasti Mercurialis annua Datura stramonium

4. 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)

5. Pre-emergence weed control in sunflower in theCzech Republic widely used tank-mix combinations of herbicides • linuron • prosulfocarb • oxyfluorfen • pendimethalin • flurochloridone • bifenox • acetochlor • alachlor • dimethenamid • metolachlor + grass weeds dicot weeds

6. Material and methodsTrial layout tested herbicides: Half of each plot was irrigated by simulationof 30 mmprecipitations (2-3 weeks after herbicide application)

7. 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:Echinochloacrus-galli, Amaranthusretroflexus, Chenopodium albumandMercurialisannua

8. Materials and methods Soil moisture conditions: dry condition – natural precipitation – 25 mm within 4 WAT wet condition – intensivenatural precipitation (65 mm within 4 WAT) simulated rainfall – (natural precipitation 25 mm within 4 WAT+ 30 mm irrigation)

9. Efficacy of tested herbicides on Amaranthus retroflexusunder different rainfall conditions low efficacy in dry condition low efficacy in dry condition

10. Efficacy of tested herbicides on Chenopodium albumunderdifferent rainfallconditions efficacy was not influenced by rainfall

11. Efficacy of tested herbicides on Echinochloacrus-galliunderdifferent rainfallconditions efficacy was not influenced by rainfall efficacy was not influenced by rainfall

12. Efficacy of tested herbicides on Mercurialis annuain different dry condition efficacy was not influenced by soil moisture

13. 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

14. Conclusions acetochlor • excellent and long-term residual efficacy onE. crus-galliand A. retroflexus • efficacy was not affected by rainfall

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

16. Conclusions acetochlor • excellent and long-term residual efficacy to E. crus-galliand A. retroflexus • efficacy was not affected by soil moisture • slowmetabolism by sunflower -risk ifused on sandy soil • sunflower injury is often hiddenand cause a growretardation

17. Conclusions oxyfluorfen • excellent efficacy on A. retroflexus and very good efficacy onM. annua – notveryinfluenced by rainfall

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

19. Conclusions oxyfluorfen • excellent efficacy onA. retroflexus and very good efficacy onM. annua – not veryinfluenced by rainfall conditions • short residual activity • slowmetabolism by sunflower – phytotoxicitywas caused by rain drops which reflected from soil surface – necrosis and deformation of leaves

20. Conclusions linuron • good efficacy on all tested weeds, but only in wet conditions • verylowefficacyin dryconditions

21. Conclusion linuron wet condition dry condition

22. Conclusion linuron • good efficacy on all tested weeds, but only in wet conditions • lowefficacyin dryconditions • relative short residual activity(up to 2 months after application)– fastdevelopmentofsunflowerleafcoverageisnecessary • high selectivity to sunflower – possibility of use on sandy soils

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

24. Conclusion flurochloridone wet conditions dry conditions

25. Conclusions prosulfocarb • excellent efficacy on all tested weeds, but only in wet conditions • in dry soil conditions, good efficacy wasfoundonly onA. retroflexus

26. Conclusion prosulfocarb wet condition dry condition

27. Conclusions prosulfocarb • excellent efficacy on all tested weeds, but only in wetconditions • in dry conditions good efficacy only onA. retroflexuswasfound • relative short residual activity • high selectivity to sunflower – possibility of use on sandy soils

28. Conclusions pendimethalin • excellent and long-term efficacy onC. album in all tested wet conditions • for other assessed weeds - short residual activityandefficacy is partially influenced by soil water conditions

29. Conclusion pendimethalin wet conditions dry conditions

30. Conclusion pendimethalin • excellent and long-term efficacy onC. album in all tested conditions • for other tested weeds - short residual activityandefficacy is partially influenced by soil watter conditions • breaking and lodging of stemsmayoccurr as a result of callus creation on stem base

31. Thank you for your attention