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“Oh Where, Oh Where Has My Pigweed Control Gone” (An Update on ALS-Resistance). Eric P. Prostko Extension Weed Specialist Department of Crop & Soil Sciences The University of Georgia Tifton. GCPA - 2005. Pigweed Problems in 2005. - PowerPoint PPT Presentation
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“Oh Where, Oh Where Has My Pigweed Control Gone”
(An Update on ALS-Resistance)(An Update on ALS-Resistance)
Eric P. ProstkoExtension Weed Specialist
Department of Crop & Soil SciencesThe University of Georgia
TiftonGCPA - 2005
Pigweed Problems in 2005
6” Pigweed Treated with 4X Rate of Cadre - Grady County (20 DAT)
Causes of Herbicide Failures
• weed size**
• moisture
• temperature
• humidity
• rate
• nozzle type
• GPA
• calibration
• bad luck
• herbicide resistance
All possible reasons for poor performance should be investigatedbefore considering the possibility of resistance!!!
ALS-Resistance Around the World
• 93 species have developed resistance world-wide
• 36 species in U.S.• Why?
– very popular• low use rates• environment friendly
– single sites of action– major MOA development in late 1980’s
early 1990’s
Herbicide Resistant WeedsBy Mode of Action
Commonly Used ALS Herbicides
• Accent• Ally• Beacon• Cadre • Classic• Envoke• Exceed• Express • Finesse
• FirstRate • Harmony Extra • Osprey• Peak• Permit/Sandea• Pursuit• Python• Scepter• Staple• Strongarm
Herbicide Resistance in Georgia
Weed Year Herbicide Location
goosegrass 1992 DNA East GA
Prickly sida 1993 IMI ?
Italian ryegrass
1995 Hoelon Peach Co. Hart Co.
Palmer amaranth
2000 2005
SU/IMI glyphosate
Burke Co. Central GA
Other Counties in Georgia with Documented ALS-Resistant Palmer Amaranth
• Tested by BASF in 2005
– Colquitt
– Cook
– Mitchell
• 166 locations were also sampled by UGA weed scientists in 2005
– ALS and glyphosate
* * *
2005 ALS-Resistant Pigweed Survey61 samples, 21 counties
If ALS-Resistance is Suspected• Prowl or Sonalan
– What about DNA-resistance?
• Cautious use of ……– Classic– Cadre– Pursuit– Strongarm
• Consider adding…..– Valor– Dual Magnum– Outlook
• Don’t be afraid of Gramoxone
• Ultra Blazer or Cobra– Tank-mix with Cadre
Do you need Gramoxone?
PE-08-05July 20, 2005 (79 DAP)Attapulgus
Untreated(1471 lbs/A)
Gramoxone Max @ 8 ozs/A+ Pledge @ 8 ozs/A + NIS
@ 0.25% v/v (15 DAP)Fb Cadre @ 1 oz/A + COC
@ 1% v/v (31 DAP)(2736 lbs/A)
Cadre @ 1 oz/A + COC @ 1% v/v (31 DAP)
(2235 lbs/A)
Postemergence Herbicide ApplicationsTimeliness is the Key!!!!
Palmer Amaranth Control with Blazer Applied at Different Timings
99
5748
0
25
50
75
100
3-5" 7-9" 11-13"
Weed Heigh t
Con
trol
(%
)
Source: Mayo et al., 1995 Weed Technology 9:141-147
Am I worried about ALS-Resistant Pigweed in Peanuts?
• The problem is real!
• It is more widespread than we would like to think.
• We have plenty of tools but ….
• We have to use them.
• Increased production costs
More Information About Herbicide Resistance
• UGA Weed Science Web-Site
* http://gaweed.com
• International Survey of Resistant Weeds
* http://www.weedscience.org/in.asp