Managing Weeds in Conservation Systems: Overcoming Herbicide-Resistant Weeds in the

Mid-South and Southeastern U.S.Andrew J. Price, Stanley A. Culpepper, Jessica A.

Kelton, Michael W. Marshall, R.L. Nichols, Jason K. Norsworthy, and L.E. Steckel

Herbicide Resistant Weeds Defy Being Rounded-Uphttp://earthshatteringgardening.blogspot.com/2010/06/herbicide-resistant-weeds-defy-being.html

Price,A.J.,K.S.Balkcom,S.A.Culpepper,J.A.Kelton,R.L.Nichols,H.Schomberg.2011.GlyphosateresistantPalmeramaranth:Athreattoconservationagriculture.J.SoilWaterConserv.66:265275

Palmer amaranth characteristics:

Rapid growth and biomass production Maximum heights of up to 72 inches (200 cm) Prolific seed production ( up to 600,000 seed

per plant) Rapid seed germination High shade tolerance (up to 87%) Shallow seed germination ( beneficial for

survival in conservation systems)

Keeley et al. 1987; Steckel et al. 2004; Burke et al. 2007; Jha et al. 2008; Fast et al. 2009; Jha and Norsworthy 2009

http://gaweed.com

Conventional Agriculture

NSDL file picture

Buries weed seed with use of moldboard plow Facilitates preplant incorporated herbicide application/ preemergence herbicide activation Provides weed/residue free seedbed Increases crop seed soil contact Provides warmer early spring soil temperature

Photo by A.C. York 2010

2004: 17% of growers hand-weeded 5% cotton acres at $2.40/A

2010: 92% of growers hand-weeded 52% cotton acres at $23.70/A

Tillage is now a common scene

2004: 13.1% of cotton acres cultivated2010: 32.1% of cotton acres cultivated

Herbicide incorporation: 264,266 A (26.7%) Deep turn: 256,075 A last 3 yr

Potential that cover crop residue can suppress weed emergence and growth Facilitates increased weed seed predation and weathering

Conservation Agriculture

NSDL file picture

Conservation AgricultureRecognition that reduced tillage accelerates buildup of seed of weed species less susceptible to applied herbicides points to the importance of maintaining acceptable levels of weed control in reduced-tillage systems beyond that necessary in systems utilizing moldboard plows. Ball (1992). It is also likely that development of herbicide-resistant weed populations will be more rapid in reduced-tillage systems due to the potential for rapid seedbank increases when control cannot be maintained.

NSDL file picture

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Weed biomass in conservation-tilled soybean as affected by cover crop and herbicide regime (51 DAP)

Black oatWheat

FallowRye

Price, A. J., D. W. Reeves, and M. G. Patterson. 2006. Evaluation of three winter cereals for weed control in conservation-tillage non-transgenic soybean. Renewable Agric. and Food Sys. 21:159-164.

Conservation Agriculture

Early Palmer Amaranth Density by Treatment - E.V. Smith 2007

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Late Palmer Amaranth Density by Treatment - E.V. Smith 2007

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Price, A. J., K. S. Balkcom, L. M. Duzy, and J. A. Kelton. 2012. Herbicide and cover cop residue integration for Amaranth control in conservation agriculture cotton. Weed Technol. 26:490-498

MaterialsandMethods

Location E.V.SResearchStation,AL

Experimentaldesign Splitsplitsplitplot

Replication Three

Plotsize Mainplot

60x9.1meter Subplot

15x9.1meter Subsubplot

3.6x9.1meter

NoHerbicide

Inversion

No-Inversion

Clover

Rye

Fallow

PrealonePostalonePre+Post

TreatmentsCont

HerbicideprogramssplitinLLsystem NoHerbicide Onlypreemergence

Prowl(2Ptacre1)+Reflex(1Ptacre1)andCaparol(24flozacre1)plusMSMA(40flozacre1)LAYBY

Onlypostemergence Ignite(29oz/A)+DualMagnumII(8oz/A)andCaparol(24flozacre1)plusMSMA(40flozacre1)LAYBY

Pre+postemergence

Palmeramaranthcontrolunderdifferenttillageandherbicideprograms

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Inversiontillageisavoidable IntegrationofcovercropsandaneffectivePRE+POSTherbicideregimewithextendedresidualactivitycaneffectivelymanagePalmeramaranthinaglufosinateresistantcottonsystem

Conclusions

Aulakh, J. S., A. J. Price, S. F. Enloe, E. Van Santen, G. Wehtje and M.G. Patterson. 2012. Palmer amaranth management in glufosinate-resistant cotton: I. tillage system, cover crops and herbicide management. Weed Management and Herbicide Resistance Special Issue. Agronomy. 2:295-311.

Aulakh, J. S., A. J. Price, S. F. Enloe, G. Wehtje and M.G. Patterson. 2013. Palmer amaranth management in glufosinate-resistant cotton: II. primary, secondary, and conservation tillage. Weed Management and Herbicide Resistance Special Issue. Agronomy. 3:28-42.

DemonstratingUseofHighResidue,CoverCropConservationTillageSystemstoControlGlyphosateResistantPalmerAmaranth

FundedNRCSConservationInnovationGrant($186,276)

Multistatecollaborativeagreementwithobjectivesto:

Demonstratesuccessfulresistantpigweedcontrolmethods

Promoteadoptionofhighresiduecovercropsystems

Providesuccessfulmodeltoproducersincorporatingthissystem

Ensureconservationtillageremainsaviablealternativetoconventionaltillagepractices

Minimum tillage to leave seed near the surface coupled with effective crop rotation/herbicide regimes could accelerate depletion of problem species from the seedbank. Ball (1992).

andrew.price@ars.usda.gov

http://ars.usda.gov/msa/auburn/nsdl

NationalSoilDynamicsLaboratoryHighlightsToSubscribe:

NSDLHighlights@ars.usda.gov

Moreinformation

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y = 99e-0.0004x (R2 = 0.70)pendimethalin

y = 92e-0.005x (R2 = 0.61)metolachlor

Potter et al. 2008. J. Envrion. Qual. 37:839-847

Do herbicides wash-off cover crop residues with irrigation?

With a 12.5 mm irrigation event, approximately 13% of the metolachlor and 0.6% of the pendimethalin washes off the cover crop residue

0.6% Pendimethalin13% Metolachlor