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Herbicide Recommendations for Noxious Pigweeds

Herbicide recommendations for management of noxious pigweeds in corn, soybean, and forages.

General Guidelines:

It is important to learn about these two invasive pigweeds (Palmer amaranth and Waterhemp).

  • Know where they are prevalent across the country.
  • Know where they have been found in Pennsylvania.
  • Know the weed biology (aggressive germination, competitiveness, seed production, and herbicide resistance).
  • Know how they spread (equipment, feed, grain, hay, manure, mulch and seed).
  • Know how to reduce their impact including preventing their movement and spread.

Develop strategies to address Palmer amaranth and Waterhemp in Commerce.

  • Identify and address pathways for the movement and spread of these weeds.
  • Identify and address effective, consistent and complementary containment measures.
  • Collaborate with academia, government and industry to take effective preventative actions.

Herbicide recommendations:

Plant into a clean seedbed.

  • use tillage or an effective burndown herbicide for no-till

Always consider herbicide sites of action (SOA) or Group numbers.

  • Use tank mixes with different effect SOAs
  • Use multiple and effective SOAs and rotate with crops
  • Avoid using the same SOA each year

Use effective soil applied herbicides at planting.

  • Use Group 14 (PPO) in soybean followed by Group 27 (HPPD) in corn. Include Group 15 herbicides in the both corn and soybean.
  • Use full labeled rates

For postemergence treatments, make timely applications and apply to small pigweed (<4 inches tall).

  • Never apply glyphosate alone to emerged pigweed
  • Avoid the use of ALS type (Group 2) herbicides for pigweed control

Scout fields within 10 to 14 days after application.

These recommendations assume Group 9 (glyphosate) and Group 2 resistance (ALS-inhibitors).

1. General Burndown herbicides for Palmer amaranth and waterhemp.
Herbicide active
SOA (Group #)
Products
2,4-D
4 various
dicamba (corn)
4 Banvel, Clarity
atrazine (corn)
5 various
simazine (corn)
5 Princep
mesotrione (corn) 27 various
glufosinate 10 Liberty
paraquat 22 Gramoxone

Soybeans

Consider planting Liberty Link soybean.

Plant into a clean seedbed.

  • Use tillage or an effective burndown herbicide for no-till

Use effective soil applied residual herbicides.

Effective preemergence herbicides are essential at or before planting.

  • sulfentrazone (Authority) or flumioxazin (Valor)-based herbicides
  • Use full labeled rates

Scout fields 10 to 14 days after application.

Apply timely early postemergence herbicide to small pigweed (<4 inches tall).

  • Reflex (1 pt) + glyphosate (or Liberty in Liberty Link soybeans)
  • Can add residual (group 15) to reduce need for another post herbicide (Dual, Warrant, Zidua/Anthem, Outlook)
2. Effective soil applied residual herbicides for soybeans.
Herbicide active SOA Products
flumioxazin 14 Valor products, Fierce, various
sulfentrazone 14 Authority products, Sonic, Broadaxe, various
saflufenacil 14 Sharpen, Verdict
linuron 7 Lorox
metribuzin 5 Sencor, Glory, Tri-Cor
pendimethalin 3 Prowl
acetoclor 15 Warrant
dimethenamid 15 Outlook
metolachlor 15 Dual
pyroxasulfone 15 Anthem, Fierce, Zidua
3. Effective Post soybean herbicides
Herbicide active SOA Products
acifluorfen 14 Ultra Blazer
fomesafen 14 Reflex, Flexstar
lactofen 14 Cobra
fluthiacet 14 Cadet
glufosinate 10 Liberty

Corn

Best option: plant corn – many more choices for management.

Apply effective residual herbicide at or before planting.

  • Atrazine premix – good
  • Lexar, Corvus + atrazine – better

Scout field 10 to 14 days after application.

Apply post herbicide when pigweed is small (<4 inches tall).

  • Better to include herbicide with residual activity in addition to dicamba, glufosinate, or 2,4-D (Atrazine, Callisto (or other mesotrione product), metolachlor, acetochlor or Zidua/Anthem)
  • Avoid glyphosate or ALS inhibitors
4. Effective soil applied residual corn herbicides.
Herbicide active SOA Products
atrazine 5 various
simazine 5 Princep
mesotrione 27 Callisto, Lumax, Lexar, Instigate, etc
isoxaflutole 27 Balance, Prefix, Prequel
pendimethalin 3 Prowl
acetochlor 15 Degree, Harness, Keystone
dimethenamid 15 Outlook
metolachlor 15 Dual
pyroxasulfone 15 Anthem, Zidua
5. Effective Post corn herbicides.
Herbicide active SOA Products
2,4-D 4 various
dicamba 4 Banvel, Clarity, Status
mesotrione 27 Callisto, Halex
topramezone 27 Impact/Armezon
tembotrione 27 Laudis, Capreno
glufosinate 10 Liberty

Forages (alfalfa, grass hay/pastures)

Routine mowing will help reduce pigweed seed production.

  • However, pigweed stumps can regrow if not cut low enough

Alfalfa could be treated with Chateau or Prowl H2O plus Gramoxone between cuttings.

In grass hay or pastures, apply 2,4-D and/or dicamba or triclopyr-containing herbicides

6. Effective forage herbicides.
Herbicide active SOA Products
2,4-D 4 various
2,4-DB 4 Butyrac, various
dicamba 4 Banvel, Clarity, Status
flumioxazin 14 Chateau
pendimethalin 3 Prowl
paraquat 22 Gramoxone
triclopyr 4 Garion, component of Crossbow

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Herbicide Recommendations for Noxious Pigweeds

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