Living and Learning withHerbicide Resistant WeedsEric P. Prostko and A. Stanley CulpepperExtension Weed SpecialistsDepartment of Crop & Soil Sciences

UGA Weed Science TeamSupporting Cast & CrewUGA FacultyTim Grey (Tifton)Bill Vencill (Athens)Mark Czarnota (Griffin)Tim Murphy (Griffin)USDA-ARSCarroll JohnsonTed WebsterPost-DocsLynn SosnoskieValdosta State Univ.Richard CarterTechnical SupportCharlie HiltonAmy DavisJesse ParkerKevin BaldreeAdministrativeDena WatsonGraduate StudentsRebekah WallaceTrey CuttsStudent WorkersToo many to mention butVery valuable to program

Palmer Amaranth in Georgia

Do what must be done?

Why Palmer Amaranth (Amaranthus palmeri)?38 species of Amaranthus in U.S.27 species found in SEdioaciousgrows faster than other pigweeds (1-2 per day!!)more competitive than other pigweedsprolific seed producerseed to seed 9-12 WAE2 generations/yearherbicide tolerance

Herbicide Resistance Concerns in Georgia glyphosate

ALS herbicides

Atrazine

Multiple resistanceGlyphosate + ALS

Georgia counties confirmed to be infested with glyphosate-resistant Palmer amaranth.2004 1 county2005 2 counties2006 7 counties2007 10 counties2008 6 so far1-28-09

GA Confirmed ALS-Resistant Palmer Sites

2008 Triazine Resistance SurveyMacon County4/20 sites resistant to 10X rate(4,5,15,20)6/20 sites took 5 qts/A to kill(3,6,8,14,17,19)

Site 5 Atrazine Resistance Survey0.115100Atrazine (qts/A)*Not resistant to Evik (ametryn) or Direx (diuron)

How did this happen to us?????Economics drive farmer decisionsNo real long-term weed mgt. planningFarm logisticsOveruse of glyphosateOveruse of Staple and CadreReduced herbicides ratesReduced tillageReduction in use of residualsDryland production systems

Palmer Amaranth BiologyHow many seed?

How long can the seed survive in the soil?

Where does most of the germination occur?

Pollen Drift

# of seedsPalmer amaranth seed production in Georgia from a single female plant when competing with cotton for the season450,000Macon Co.2006*1,000,000 seed/plant (Keeley et al. 1987. Weed Science 35:199-204)California

R-Palmer amaranth seed longevitySource: Dr. Lynn Sosnoskie - UGA

Influence of burial depth on Palmer amaranth emergence in GeorgiaSource: Dr. Lynn Sosnoskie - UGA

Herbicide Resistant WeedsPollen DriftOff-site movement (wind, gravity, insects, man, animal) of resistance trait through pollen

Pollen from resistant male fertilizes susceptible female to produce resistant progeny (seed)

UGA researchers have documented GR-trait movement of at least 960 (Palmer amaranth).Palmer Amaranth PollenSource: Dr. Lynn Sosnoskie

In-field Palmer amaranth pollen movement

Cultural PracticesDeep tillage

Extreme cover crops

No Deep TillageDeep TurnNo Herbicide Treatment

Palmer amaranth seedling density as influenced by tillage.

Dryland Systems

Irrigation in GeorgiaSource: Kerry Harrison, UGA Extension Engineer

May-June 2008 Rainfall Distribution in Midville Crops planted from May 21-June 21 did not receive enough rainfall to activate herbicides (0.26 total).June Rainfall = 0.62 which occurred as follows:12 (0.08); 22 (0.36); 26 (0.08); 29 (0.10)

If residual herbicides are not activated on a timely basis with a reliable water source, pigweed control will be very difficult, maybe even impossible!

Dryland SystemsGrowers need to think about mechanical herbicide incorporation

Will help but not a guarantee

Success will depend uponoperatorImplementSoil conditions

Chemical Control OptionsValor (flumioxazin)Reflex (fomesafen)Dual Magnum (S-metolachlor)AtrazineLiberty-Link (glufosinate)Sencor products (metribuzin)KIH-485

Palmer Amaranth Control in PeanutsMacon County, GA 2007 (38 DAT)NTCValor SX 51WG @ 3 oz/A

Palmer Amaranth Control in PeanutsMacon County, GA 2007 (38 DAT)NTCDual Magnum 7.62EC@ 1 pt/A

NTCAtrazine 4L @ 1 qt/A PREAtrazine 4L @ 1.5 qt/A 30 DAPPeptoil @ 1% v/v 30 DAPMacon County GR Palmer AmaranthJune 24, 2008 60 DAPCN-01-08

RR vs LL Corn - 2008UntreatedRoundup W-Max @ 22 oz/AAtrazine @ 1.5 qt/AProwl H2O @ 2.1 pt/A(POST)Ignite 2.34 SL @ 23 oz/AAtrazine @ 1.5 qt/AProwl H2O @ 2.1 pt/AAMS @ 3 lb/A(POST)CN-11-086/17/200881 DAP

Metribuzin Products on SoybeansSencorBoundaryDual Magnum + SencorCanopySencor + ClassicRead labelKnow soil texture and OMVarietiesrotations

GR-Pigweed Control in Soybeans - 2008SB-06-08Macon County48 DAPNTCCanopy 75DG @ 6 oz/A + Prowl H2O 3.8ASC @ 2.1 pt/A (PRE)

GR-Palmer Amaranth Control in Soybeans - 2007SB-01-07Macon Co.76 DAPNTCGramoxone Inteon @ 3 pt/A +Boundary @ 1.8 pt/A + NIS @ 0.25% v/v (7 DBP)Touchdown Total @ 1.5 pt/A (26 DAP)

Soybean varieties screened in 2008 that had adequate tolerance to Boundary 6.5EC (2 pt/A), Canopy 75DG (5 oz/A), and Sencor 75DG (6 oz/A). Ag South AGS 568 Asgrow H7242Asgrow 4903 RR/STS Delta Pineland DP 5634Delta Pineland DP 6568 Northrup King NKS 80P2Northrup King NKS 76L9Northrup King NKS 78G6Pioneer 95Y40Pioneer 95Y70Pioneer 96M60Pioneer 97M50Southern States RT5951Southern States RT4808Vigoro V61N9Vigoro V74N9

GR-Pigweed Control in Soybeans 2008 Macon County90%Valor @ 3 oz/A; Envive @ 3 oz/A; Reflex @ 1 pt/A;Prefix @ 2 pt/A; Canopy @ 6 oz/A; Sencor @ 8 oz/AKIH-485 @ 4.2 oz/A; Dual Magnum @ 1 pt/A

KIH-485PyroxasulfoneKumiaiDeveloped for corn and soybeansPREHerbicide FamilySulfonylioxazoline (?)Herbicide Mode of Action (?)plant growth inhibitor that affects apical meristem and coleoptile development of plants after seed germinationLow use rates

GR-Palmer Amaranth Control in Soybeans with PREs (2008) - Macon Co.NTCKIH-485 85WG @ 4.2 oz/ASB-05-0848 DAT

Under Utilized Modes of ActionHPPD-inhibitorsMesiotrione (Callisto)Tembotrione (Laudis)Topramezone (Impact)

Halex GT in Field Corn - 2008UntreatedCN-05-086/19/200883 DAPHalex GT 4.39L4 pt/A + NIS(POST)

Dont forget!!! There are no steel resistant weeds!!!

We are overusing the PPO inhibiting herbicides!!!!!!!!Resistance has already been reported in other areas!!!

Common waterhemp2001 (Kansas)2002 (Illinois)2003 (Missouri)

Common ragweed2005 (Delaware)

Wild poinsettia2004 (Brazil)

For More Weed Science Info:www.gaweed.com

eprostko@uga.edu

229-386-3328 (office)

229-392-1034 (cell)