1. Managing ALS-Resistant Palmer Amaranth in Peanuts
Eric P. Prostko
Extension Weed Specialist
Department of Crop & Soil Sciences
The University of Georgia

2. What does ALS mean? Herbicide families Acetolactate synthase (ALS)
Acetohydroxyacid synthase (AHAS)
chloroplast enzyme needed to form certain amino acids
Valine, leucine, isoleucine
Herbicide families
Imidazolinones
Sulfonylureas
Sulfonanalides
benzoates

3. Commonly Used ALS Herbicides
Accent
Ally/Cimarron
Beacon
Beyond
Cadre
Classic
Envoke
Exceed
Express
Finesse
FirstRate
Glean
Harmony Extra
Maverick Pro
Osprey
Peak
Permit
Pursuit
Python
Scepter
Staple
Strongarm

4. Managing ALS-Resistant Palmer Amaranth in Peanuts
Weed-free at planting
Preemergence herbicides
Prowl or Sonalan on every acre + ?
Postemergence herbicides
Cultivation
Harvest Aids
Rope-wick applications
Mowing
Other tactics
Crop rotation with corn (atrazine)

5. Preemergence Herbicides
Valor
Dual Magnum
Generic Metolachlors
Outlook/Propel
What about…..
Reflex
Goal
Solicam
activation

6. Metolachlor Mysteries

7. GR-Pigweed/Soybean Test – II (2006) 7 WAP
RUWM (POST)
2 oz/A (PRE)
RUWM (POST)
Untreated

8. Valor in Peanuts - The Bottom Line
Plant at least 1.5” deep and apply within 2 days of planting
Injury will occur if heavy rainfall occurs from cracking until ~2 WAC
peanut yield should not be reduced if stand is not lost
hose and nozzle clean-out very important!!!!!
except this or do not use it
Glyphosate was developed as an industrial cleaner!!

9. Valor Injury in Peanut

10. Postemergence Herbicides
Timing, timing, timing
16” in 1 week
Paraquat
G-Inteon
Firestorm
15 GPA
flat fan nozzles
tractor speed
Cobra
Ultra Blazer
Storm
2,4-DB
Cobra, Storm, Ultra Blazer, Valor have the same mode of action (PPO inhibitors)

11. How/Why do we let pigweeds get this big????

12. Will these herbicides control large pigweeds?

13. Cobra 2EC @ 12.5 ozs/A + COC @ 1% v/v applied to 17” tall pigweed
4 DAT
1 DAT
7 DAT
16 DAT

14. 2,4-DB/Cobra Test – 2006 Untreated Cobra 2EC @ 12.5 oz/A
1% v/v
POST
2,4-DB 1.1 pt/A +
1% v/v (POST) fb
Cobra 12.5 oz/A
1% v/v
POST2
POST: June 5 (17” tall pigweed)
POST2: June 9
Photos taken 24 days after POST application

15. Does Cobra reduce yields??

16. Peanut (GA Green) Response to Cobra 78 DAP - 2006
3556 lbs/A – Tifton
4450 lbs/A - Plains
4003 lbs/A – Tifton
4319 lbs/A - Plains
Untreated
ozs/A
1% v/v
Applied 30 DAP

17. PPO Resistance??? PPO or Protox Protoporphyrinogen oxidase
Enzyme found in chloroplast and mitochondria
3 species worldwide
Common waterhemp
Kansas (2001)
Illinois (2002)
Common ragweed
Delaware (2005)
Wild poinsettia
Brazil (2004)\
Ultra Blazer, Cobra, Goal, Reflex, Ronstar, Resource, Aim, Valor, Storm, Spartan

18. Where do Cadre and Strongarm fit in?
Effective on many other weeds
Cadre is the only herbicide that will control purple nutsedge

19. Cadre @ 4 ozs/A + 2,4-DB @ 1.1 pt/A + COC @ 1% v/v – 34 DAT
Applied to 17” tall pigweed

20. Cultivation (no weeds are steel-resistant!!!)
Time
Diesel fuel prices
Strip-tillage
Twin rows
White mold

21. Rope-wick Applicators
glyphosate is labeled for wiper applications in row middles
33-50% solution
Opposite directions
5 MPH or less
GR-pigweed concerns??

22. Mowing Weed/peanut height differential Digging and harvest aid
Flail mower better than rotary mower
diesel fuel prices
Time???

23. What if we do not control Palmer amaranth?
Crop
(State)
Density
Yield Loss
Source
Corn
(KS)
0.5-8 plants/m
11-91%
Weed Sci.
2001
49:
Soybean
(AK)
plants/m
17-68%
1994
42:
Grain sorghum
(OK)
1-18 plants/15 m
4-63%
Weed Tech.
2004
18:23-29
Peanut
(NC)
1-5 plants/m
28-66%
Burke and Wilcut
(in-press)
Cotton
(TX)
1-10 plants/9.1 m
13-54%
15: