of Glyphosate-Resistant Palmer Amaranth in the Southeast Herbicide - - PowerPoint PPT Presentation

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of Glyphosate-Resistant Palmer Amaranth in the Southeast Herbicide - - PowerPoint PPT Presentation

Jul 17, 2023 246 likes •582 views

Distribution, Impact, and Management of Glyphosate-Resistant Palmer Amaranth in the Southeast Herbicide Resistance in US by Mode of Action Nitriles Carotenoid biosyn. inhibitors PPO inhibitors Bipyridiliums Thiocarbamates Arsenicals Auxins

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Distribution, Impact, and Management

  • f Glyphosate-Resistant Palmer

Amaranth in the Southeast

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20 40 60 80 100 120

  • No. cases

ALS inhibitors PS II inhibitors (triazines) ACCase inhibitors Glycines DNA’s Ureas Auxins Arsenicals Bipyridiliums Thiocarbamates PPO inhibitors Carotenoid biosyn. inhibitors Nitriles

Herbicide Resistance in US by Mode of Action

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Glyphosate-resistant weeds in U.S.1 AL FL GA NC SC VA Common ragweed X Common waterhemp Giant ragweed Hairy fleabane Horseweed X Italian ryegrass Johnsongrass Rigid ryegrass Palmer amaranth XXX XXX XXX

1 Weedscience.org

Glyphosate-Resistant Weeds in Southeast

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Glyphosate-resistant Palmer amaranth in Georgia, as of end of 2007

20 counties; 300,000 acres Severe infestation 100,000 acres

  • Mod. infestation

100,000 acres “Hot spots” 100,000 acres

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Lee Darlington Dillon

Glyphosate-resistant Palmer amaranth South Carolina, 2006

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290 fields sampled for screening in fall of 2005.

Number indicates number of fields sampled.

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Resistant Palmer amaranth in 49 of 290 fields sampled in fall of 2005

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Glyphosate-resistant Palmer amaranth, 2008. 22 counties, up to 200,000 acres Severe infestation 75,000 acres

  • Mod. infestation

75,000 acres “Hot spots” 50,000 acres

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Why are we seeing more and more glyphosate-resistant Palmer amaranth?

  • Continued spread

– Seed movement, primarily by equipment. – Trait transferred via pollen.

  • Resistance trait carried by pollen.
  • Pollen can move, fertilize females 1000 ft.
  • Implications: if you have susceptible females and your

neighbor has resistance, look out!

  • Continued selection
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Impacts of GR Palmer Amaranth in Southeast

  • 1. Lot of anxiety
  • 2. More cultivation (GA, SC),

less no-till (GA); 3-5% acreage

  • 3. Increase in use of residuals,
  • ther MOA‟s
  • 4. More hand-weeding
  • 5. Increased production costs
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Herbicide Resistance Management The focus must be on reducing selection pressure.

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Back: Untreated Front: Roundup only

  • Roundup Ready allowed

us to be “weed sprayers”

  • Resistance will force us to

become weed managers

  • Greater complexity
  • Increased costs
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In-Crop Glyphosate Resistance Management

  • 1. Do not depend entirely on glyphosate;

Incorporate other herbicides (other MOA‟s) into RR systems

  • i. Residual herbicides preplant or preemergence;

residuals have a fit

  • ii. Tank mixes postemergence
  • iii. Full-use rates
  • 2. Non-chemical control where it fits
  • 3. Watch carefully for escapes; eliminate them before

seeding out

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Detect Resistance Early

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Considerations in Planning Palmer Amaranth Management Systems

  • Problem likely to get worse
  • No salvage options for cotton; POST options for

corn and soybean IF timely

  • ALS resistance widespread; can‟t depend on that

chemistry; need to reduce further selection

  • PPO inhibitors important now and into foreseeable

future; must “protect” that chemistry

  • Must focus on reducing seed bank; i.e., consistently

good control in all crops in rotation for several years

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Multiple glyphosate applications, soybeans, Wayne Co., NC 2005

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Herbicide programs for Palmer amaranth in RR cotton

Glyphosate resistance ALS resistance Preplant

  • r PRE

POST Layby No No

  • r

Yes Cotoran, Direx, or Prowl PRE

  • r

Light: Roundup MSMA + Direx MSMA + Layby Pro MSMA + Suprend** MSMA + Valor**

  • r

R‟up + Direx R‟up + Layby Pro R‟up + Suprend** R‟up + Valor*** Valor preplant followed by Cotoran, Direx, or Prowl PRE Heavy: Roundup + Dual Magnum

* Note multiple MOA‟s, even with an “easy” situation. Note lack of ALS inhibitors. ** Suprend not suggested if ALS-resistant Palmer expected. *** Try to limit PPO inhibitors (such as Valor and Reflex) to one application per year.

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Herbicide programs for Palmer amaranth in RR cotton

Glyphosate resistance ALS resistance Preplant

  • r PRE

POST Layby No No

  • r

Yes Cotoran, Direx, or Prowl PRE

  • r

Light: Roundup MSMA + Direx MSMA + Layby Pro MSMA + Suprend** MSMA + Valor**

  • r

R‟up + Direx R‟up + Layby Pro R‟up + Suprend** R‟up + Valor*** Valor preplant followed by Cotoran, Direx, or Prowl PRE Heavy: Roundup + Dual Magnum

* Note multiple MOA‟s, even with an “easy” situation. Note lack of ALS inhibitors. ** Suprend not suggested if ALS-resistant Palmer expected. *** Try to limit PPO inhibitors (such as Valor and Reflex) to one application per year.

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Herbicide programs for Palmer amaranth in RR cotton*

Glyphosate resistance ALS resistance Preplant

  • r PRE

POST Layby Yes No Direx + Reflex, Direx + Staple, or Reflex + Staple PRE

  • r

No emerged Palmer: Roundup + Dual Magnum MSMA + Direx MSMA + Layby Pro MSMA + Suprend MSMA + Valor** Valor preplant followed by Direx + Staple or Prowl + Staple Palmer < 2in.: Roundup + Staple * Strong PRE program. Try to limit ALS inhibitors (Staple, Envoke) and PPO inhibitors (Reflex,Valor) to one application per year.

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Herbicide programs for Palmer amaranth in RR cotton*

Glyphosate resistance ALS resistance Preplant

  • r PRE

POST Layby Yes Yes Direx + Reflex or Prowl + Reflex PRE

  • r

Valor preplant followed by Direx + Prowl Before Palmer emergence: Roundup + Dual Magnum MSMA + Direx MSMA + Layby Pro MSMA + Valor * Try to limit PPO inhibitors (Reflex and Valor) to one application per year.

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Glyphosate-resistant Palmer amaranth management in NC cotton

Herbicide program: Aggressive preplant/preemergence program. Preemergence critical; cannot “salvage” postemergence. Dual Magnum overtop for additional residual control. Residual herbicide(s) lay-by. Cultivation: Very unpopular; growers don’t want to resort to that. About 70% of cotton strip-till or no-till. Preplant incorporated herbicides: Same situation as cultivation

  • Roundup. + 2,4-D

burndown

  • Gram. + Reflex PRE

Roundup + Dual first POST Roundup second POST Direx + MSMA Layby

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Glyphosate-resistant Palmer amaranth management in NC soybean Herbicide program: Aggressive preplant/preemergence program. POST herbicides/tank mixes as needed. Max size for POST depends on product; no label > 8 inches.

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Herbicide programs for Palmer amaranth in RR soybean

Soybean variety Glyphosate resistance ALS resistance PRE POST RR No; Lighter infestation Yes or No Boundary, Canopy, Dual Magnum, Envive, Intrro, Prefix, Prowl, Reflex, Sencor, or Valor Roundup No: Heavy infestation Yes or No Roundup

  • r

R‟up + Dual Mag.

  • r

Sequence

  • r

R‟up + Flexstar*

* Limit PPO inhibitors (Envive, Prefix, Reflex, Valor) to one application per year.

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Soybean variety Glyphosate resistance ALS resistance PRE* POST* RR Yes No Boundary; Canopy; Envive; Intrro; Prefix; Reflex; Sencor; or Valor R„up+ Harmony SG** R‟up + Flexstar R‟up + Reflex R‟up + Blazer Yes Yes Boundary; Canopy + Dual Mag, Intrro, or Prowl; Envive + Prowl; Valor + Prowl R‟up + Flexstar R‟up + Reflex R‟up + Blazer * Limit PPO inhibitors (Envive, Prefix, Reflex, Valor) to one application per year. Products in red are not PPO inhibitors or ALS inhibitors. ** Harmony SG is an ALS inhibitor.

Herbicide programs for Palmer amaranth in RR soybean*

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Mount Olive, NC 2008

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