How Serious is the Herbicide Resistant Weed Issue

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How Serious is the Herbicide Resistant Weed
Issue?

• Eric P. Prostko
• Extension Weed Specialist
• Department of Crop Soil Sciences

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Is the sky falling? Did it already fall?
Chicken Little
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Consequences of Resistance?Macon County, Georgia
(2008)
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Herbicide Resistant WeedsSelection Pressure
Source J.L. Gunsolus. Herbicide Resistant
Weeds. 1998. North Central Region Extension
Publication 468.
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Herbicide Resistant WeedsPollen Drift

• Off-site movement (wind, gravity, insects) of
  resistance trait through pollen
• Pollen from resistant male fertilizes susceptible
  female to produce resistant progeny
• UGA researchers have documented GR-trait movement
  of at least 900 (Palmer amaranth).

Palmer Amaranth Pollen Source Dr. Lynn Sosnoskie
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The US Wins the Gold Medal in Resistance!!!!
Source International Survey of Herbicide
Resistant Weeds (6/4/09) 4 France (32) 5
Spain (31)
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Worldwide Number of Glyphosate Resistant Weeds By
Year (Cumulative)(Roundup was first introduced
in 1974)
Source International Survey of Herbicide
Resistant Weeds (6/4/09)
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Confirmed Number of Herbicide Resistant Weeds in
the Peanut Belt
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10
11
3
15
5
1
5
3
12
5
7
5
Source International Survey of Herbicide
Resistant Weeds (6/4/09)
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How did all this happen?????

• Economics drive farmer decisions
• No real long-term weed mgt. planning
• Farm logistics
• timeliness
• Overuse (abuse) of glyphosate
• Staple/Cadre in cotton/peanut
• Reduced herbicides rates
• Reduced tillage
• Reduction in use of residuals
• Reduction in cultivation
• Dryland production systems

Glyphosate-Resistant Palmer Amaranth Macon
County, Georgia
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What can we do about it now!

• Must understand modes of action
• Start clean!
• Skimp up front, pay later
• Conventional tillage if needed/practical
• Dryland, reduced tillage systems are in
  jeopardy!!!
• Use a RESIDUAL herbicide in ALL crops!
• Prevent escaped weeds from going to seed!

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2009Macon CountyGR-Palmer Tests
PRE
No PRE
18 DAP
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2009 GR-Palmer Amaranth TestMacon County
NTC
Boundary 6.5EC 1.75 pt/A PRE
SB-06-09 May 15, 2009 24 DAT
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Herbicide Modes of Action

• Do not worry about the technical stuff!
• Check the label
• Local Extension Service
• Herbicide Resistance Action Committee (HRAC)
• http//www.hracglobal.com/
• Know what you are spraying!!

2,4-D chemical structure
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Under Utilized Herbicide Modes of ActionCan we
use them?????

• HPPD-inhibitors
• Mesiotrione (Callisto)
• Tembotrione (Laudis)
• Topramezone (Impact)
• Isoxaflutole (Balance Flexx)

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Palmer Amaranth Control in Field Corn with HPPD
Herbicides - 2009
Corvus 2.6SC _at_ 3.33 oz/A PRE (April 11) Photo
June 4 (54 DAT)
NTC
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We are overusing the PPO inhibiting
herbicides!!!!!!!!

• Resistance has already been reported in other
  areas!!!
• Common waterhemp
• 2001 (Kansas)
• 2002 (Illinois)
• 2003 (Missouri)
• Common ragweed
• 2005 (Delaware)
• Wild poinsettia
• 2004 (Brazil)

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A long-term resistance plan?
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For More Weed Science Infowww.gaweed.com
eprostko_at_uga.edu 229-386-3328 (office) 229-392-1
034 (cell)