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ManagingHerbicide Resistance         Bob Hartzler   Extension Weed Science   Department of Agronomy
Evolution of Row Crop        Weed Management   Cultural +          Chemical +                                     Chemical...
Important Resistant         Weeds in IowaDecade Herbicides         Weeds1980’s   Triazines        Pigweed, lambsquarter199...
Resistance Mechanisms     in WaterhempFamily            Herbicides              MechanismTriazines         Atrazine, metri...
Why Waterhemp?
Seed ProductionResistance is a numbers game       Time of     Soybean   Corn       emergence       With crop   320,000   4...
‘Standard’ Resistance   Management Strategies• Fundamentals  – Start with clean fields  – Use weed-free seed  – Scout fiel...
‘Standard’ Resistance   Management Strategies• Herbicide management  – Rotate crops to allow alternate herbicides  – Use m...
‘Standard’ Resistance   Management Strategies• Miscellaneous tactics  – . . . and add cultural practices  – Consider mecha...
YEAR   PRE     POST                           MOA1999   Dual    Basagran + atrazine             32000   Prowl   Glyphosate...
Keys to Resistant     Weed Management• Know your enemy• Optimize herbicide effectiveness
Evolution of Herbicide Rates                          Full label rate   Acetochlor Flumetsulam ClopyralidPre RR           ...
Keys to Resistant       Weed Management• Cultural practices  – Manipulation of cropping conditions to    reduce the densit...
Effects of Cultural Practices in Nebraska Wheat FieldsRow Direction                   Drill Type          E-W     N-S     ...
Value of Cultural Practices
Value of Cultural Practices Preemergence          No PreGlyphosate at V3   Glyphosate at V3
Value of Cultural Practices
Cultural Practices For          An Herbicide Era•   Row spacing•   Planting rate•   Planting date•   Variety characteristics
Herbicide Resistance• Weeds adapt to all tactics, all herbicides• The greater the reliance on a tactic, the  greater the s...
Questions
Crop Management - Dr. Robert G. Hartzler, Iowa State University - Managing Herbicide Resistance
Crop Management - Dr. Robert G. Hartzler, Iowa State University - Managing Herbicide Resistance
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Crop Management - Dr. Robert G. Hartzler, Iowa State University - Managing Herbicide Resistance

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Attendees will gain a basic understanding of the processes influencing herbicide availability which is essential to diagnose performance issues in the field.

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Transcript of "Crop Management - Dr. Robert G. Hartzler, Iowa State University - Managing Herbicide Resistance"

  1. 1. ManagingHerbicide Resistance Bob Hartzler Extension Weed Science Department of Agronomy
  2. 2. Evolution of Row Crop Weed Management Cultural + Chemical + Chemical mechanical mechanical1900 1920 1940 1960 1980 2000 2010
  3. 3. Important Resistant Weeds in IowaDecade Herbicides Weeds1980’s Triazines Pigweed, lambsquarter1990’s ALS inhibitors Waterhemp, cocklebur, foxtails, several others2000’s Glyphosate Waterhemp, horseweed, giant ragweed PPO inhibitors Waterhemp2010’s HPPD inhibitors Waterhemp www.weedscience.org
  4. 4. Resistance Mechanisms in WaterhempFamily Herbicides MechanismTriazines Atrazine, metribuzin Altered target site, Enhanced metabolismALS inhibitors Pursuit, Classic Altered target sitePPO inhibitors Blazer, Cobra, Reflex Altered target siteGlyphosate Roundup Target site amplification, perhaps othersHPPD inhibitors Callisto, Laudis UnknownGrowth regulators 2,4-D Unknown
  5. 5. Why Waterhemp?
  6. 6. Seed ProductionResistance is a numbers game Time of Soybean Corn emergence With crop 320,000 48,000 V4 20,000 2,000
  7. 7. ‘Standard’ Resistance Management Strategies• Fundamentals – Start with clean fields – Use weed-free seed – Scout fields – Control weed escapes – Clean equipment between fields www.monsanto.com www.resistancefighter.com
  8. 8. ‘Standard’ Resistance Management Strategies• Herbicide management – Rotate crops to allow alternate herbicides – Use multiple herbicides – Use full rates www.monsanto.com www.resistancefighter.com
  9. 9. ‘Standard’ Resistance Management Strategies• Miscellaneous tactics – . . . and add cultural practices – Consider mechanical control – Use cover crops www.monsanto.com www.resistancefighter.com
  10. 10. YEAR PRE POST MOA1999 Dual Basagran + atrazine 32000 Prowl Glyphosate 22001 Dual Callisto 22002 Prowl Glyphosate 22003 Dual Accent + atrazine (E-POST) 4 Callisto + atrazine (L-POST)2004 Prowl Glyphosate 22005 Dual Accent + Callisto + atrazine 42006 Prowl Glyphosate 22007 Dual Callisto + atrazine (E-POST) 3 Impact + atrazine (L-POST)2008 Prowl Glyphosate 22009 Dual Callisto + atrazine 3
  11. 11. Keys to Resistant Weed Management• Know your enemy• Optimize herbicide effectiveness
  12. 12. Evolution of Herbicide Rates Full label rate Acetochlor Flumetsulam ClopyralidPre RR 3 pts Harness + 2.6 lbs 0.9 oz 2.5 oz 5 oz HornetPost RR 2 pts SureStart 36% 50% 50%Post RRv2.0 3 pts SureStart 54% 75% 75% % herbicide remaining Waterhemp emergence # emerged/week April May June July
  13. 13. Keys to Resistant Weed Management• Cultural practices – Manipulation of cropping conditions to reduce the density and competitiveness of weeds or
  14. 14. Effects of Cultural Practices in Nebraska Wheat FieldsRow Direction Drill Type E-W N-S Disk Hoe40 630 420 210 0 0 LQ Pig Grass Fox Kochia Stinkgrass 8 Others Wicks et al. 2003. Weed Technol.
  15. 15. Value of Cultural Practices
  16. 16. Value of Cultural Practices Preemergence No PreGlyphosate at V3 Glyphosate at V3
  17. 17. Value of Cultural Practices
  18. 18. Cultural Practices For An Herbicide Era• Row spacing• Planting rate• Planting date• Variety characteristics
  19. 19. Herbicide Resistance• Weeds adapt to all tactics, all herbicides• The greater the reliance on a tactic, the greater the speed of adaption• Integrated management programs needed to stay ahead of evolution
  20. 20. Questions
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