Herbicide Resistance:Herbicide Resistance:Protecting the PPO’sProtecting the PPO’s

Eric P. ProstkoEric P. ProstkoExtension Weed SpecialistExtension Weed Specialist

Dept. of Crop & Soil SciencesDept. of Crop & Soil SciencesThe University of GeorgiaThe University of Georgia

Herbicide ResistanceHerbicide ResistanceDefinitionDefinition

•• WSSA definitionWSSA definition•• “the “the inheritedinherited ability of ability of

a plant to survive and a plant to survive and reproduce following reproduce following exposure to a dose of exposure to a dose of herbicide normally herbicide normally lethal to the wild type”lethal to the wild type”

ALS-Resistant Palmer Amaranthin Peanuts

Herbicide ResistanceHerbicide ResistanceWhy????Why????

•• Selection PressureSelection Pressure–– Overuse of single Overuse of single

product or MOAproduct or MOA

•• Pollen DriftPollen Drift–– Resistant trait moves Resistant trait moves

thru pollenthru pollen

Palmer Amaranth PollenPalmer Amaranth Pollen

PPO Inhibiting HerbicidesPPO Inhibiting Herbicides

•• PPO or ProtoxPPO or Protox–– Protoporphyrinogen oxidaseProtoporphyrinogen oxidase–– Enzyme found in chloroplast Enzyme found in chloroplast

and mitochondria needed for and mitochondria needed for formation of chlorophyllformation of chlorophyll

–– Cell membrane destructionCell membrane destruction

•• Many common herbicides have Many common herbicides have this mode of action!!this mode of action!!–– Ultra Blazer, Cobra, GoalUltra Blazer, Cobra, Goal, ,

Reflex, Ronstar, Resource, Reflex, Ronstar, Resource, Aim, Valor, Storm, Spartan, Aim, Valor, Storm, Spartan, ETET

Glyphosate and ALS resistance is forcing Glyphosate and ALS resistance is forcing GA growers to rely on PPO herbicides!!!GA growers to rely on PPO herbicides!!!

ALS-Palmer AmaranthGR-Palmer Amaranth

Palmer Amaranth Control in PeanutsPalmer Amaranth Control in PeanutsMacon County, GA Macon County, GA –– 2007 (38 DAT)2007 (38 DAT)

NTC Valor SX 51WG @ 3 oz/A

GRGR--Palmer Amaranth Control in Palmer Amaranth Control in Soybean Soybean –– 2007 (83 DAT)2007 (83 DAT)

Untreated Prefix 5.29EC @ 2 pt/ASB-01-07

What the heck is Prefix???What the heck is Prefix???

•• 5.29 SC formulation5.29 SC formulation–– 4.34 lbs Dual Magnum4.34 lbs Dual Magnum–– 0.95 lb Reflex0.95 lb Reflex

•• Use rate is 2 pt/A ($10.50)Use rate is 2 pt/A ($10.50)–– At 2 pts/A you get the following…….At 2 pts/A you get the following…….–– 1.085 lb ai of Dual Magnum (18.2 ozs/A)1.085 lb ai of Dual Magnum (18.2 ozs/A)–– 0.2375 lb ai of Reflex (15.2 ozs/A)0.2375 lb ai of Reflex (15.2 ozs/A)

High Potential to Overuse (Abuse)High Potential to Overuse (Abuse)Reflex and ValorReflex and Valor

YesYes(PPLNT)(PPLNT)(LAYBY)(LAYBY)

YesYesYesYes(PPLNT)(PPLNT)

YesYesValorValor

YesYesYesYesNoNoNo (?)No (?)ReflexReflex

CottonCottonSoybeanSoybeanCornCornPeanutPeanutHerbicideHerbicide

PPO Resistance Already Exists!PPO Resistance Already Exists!•• Common waterhempCommon waterhemp

–– 2001 (KS)2001 (KS)• Resistant to POST but not PRE

–– 2002 (IL)2002 (IL)–– 2005 (MO)2005 (MO)

•• Common ragweedCommon ragweed–– 2005 (DE)2005 (DE)

•• Wild poinsettiaWild poinsettia–– 2004 (Brazil)2004 (Brazil)

*

Preventing PPO Resistance in GAPreventing PPO Resistance in GA•• Know modes of actionKnow modes of action

•• Should we save the PPO herbicides for our 2 most Should we save the PPO herbicides for our 2 most important row crops (cotton, peanuts)???important row crops (cotton, peanuts)???–– 1.7 million acres (cotton + peanuts) vs. 0.78 million acres (soy1.7 million acres (cotton + peanuts) vs. 0.78 million acres (soybeans + corn)beans + corn)

•• Rotate cropsRotate crops–– Corn (atrazine, Callisto, 2,4Corn (atrazine, Callisto, 2,4--D, Status)D, Status)–– Soybeans (Dual Magnum, Sencor)Soybeans (Dual Magnum, Sencor)

•• Try not to use a PPO more than once per crop per yearTry not to use a PPO more than once per crop per year–– i.e. Do not use Valor and Reflex on cotton in the same yeari.e. Do not use Valor and Reflex on cotton in the same year–– 22--11--2 program???2 program???–– What about peanuts????What about peanuts????

• Valor, Cobra, Ultra Blazer, Storm

Preventing PPO Resistance in GAPreventing PPO Resistance in GA

•• Include other residual herbicides with PPO’sInclude other residual herbicides with PPO’s–– Dual Magnum, Intrro, OutlookDual Magnum, Intrro, Outlook–– Treflan, Prowl, SonalanTreflan, Prowl, Sonalan–– Boundary (Sencor + Dual Magnum)Boundary (Sencor + Dual Magnum)–– Prefix (Reflex + Dual Magnum)Prefix (Reflex + Dual Magnum)

Preventing PPO Resistance in GAPreventing PPO Resistance in GA

•• Use other weed control tacticsUse other weed control tactics–– CultivationCultivation

• No known cases of steel-resistance have been reported

• Diesel fuel prices and time are major deterrents

–– HandHand--rogueing (seedrogueing (seed--bank bank control)control)

•• Do not want to but may have Do not want to but may have to!!!to!!!

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