Effective Pesticide Application Reeves Petroff Pesticide Education Specialist MSU Extension

Effective Pesticide Application

Reeves Petroff

Pesticide Education Specialist

MSU Extension

http://MTPESTICIDES.org

Effective Pesticide ApplicationEffective Pesticide Application

Should not be Should not be Confusing !Confusing !

A Basic Understanding of A Basic Understanding of

Or Or PainfulPainful ! !

but it can be!!but it can be!!

The Pesticide Application ProcessThe Pesticide Application Process

The Spray SolutionThe Spray Solution

AtomizationAtomization

Transport to TargetTransport to Target

Impaction / DepositionImpaction / Deposition

Post-Impact Drop Behavior Post-Impact Drop Behavior Spreading, Retention, Penetration, TranslocationSpreading, Retention, Penetration, Translocation

Biological EffectBiological Effect

Contact ActionContact Action Systemic ActionSystemic Action

Spray Solution - Water Spray Solution - Water

• Primary diluent Primary diluent

• Large percentage of spray solution Large percentage of spray solution volumevolume

• Can have a negative influence on Can have a negative influence on pesticide performance. pesticide performance.

pH

Minerals

Acidity / Alkalinity (pH)Acidity / Alkalinity (pH)

Affects:Affects:

a.a. The chemical stability of some The chemical stability of some pesticidespesticidesb.b. The dissociation and subsequent The dissociation and subsequent penetration of weak-acid herbicidespenetration of weak-acid herbicidesc.c. The physical stability of the The physical stability of the formulation upon dilution formulation upon dilution

Chemical Stability of PesticidesChemical Stability of Pesticidesas related to pHas related to pH

Many pesticides are unstable under alkaline conditions Many pesticides are unstable under alkaline conditions that is pH levels above 7.0 that is pH levels above 7.0

Alkaline hydrolysisAlkaline hydrolysis..

Stability is usually referenced in terms of “half-life”.Stability is usually referenced in terms of “half-life”.

What is Meant by the Term What is Meant by the Term “Half-Life”?“Half-Life”?

It is the time required for It is the time required for degradation to 50% of the original degradation to 50% of the original amount of the pesticideamount of the pesticide

It is used as a standard to describe It is used as a standard to describe the relative stability of a pesticide.the relative stability of a pesticide.

Examples of Stability Examples of Stability relative to pH relative to pH

InsecticidesInsecticidesBendiocarbBendiocarbCarbarylCarbarylDimethoateDimethoateTrichlorfonTrichlorfon

Half-LifeHalf-Life45 min pH 945 min pH 93.2 hrs pH 93.2 hrs pH 948 min pH 948 min pH 963 min pH 863 min pH 8

FungicidesFungicidesCaptanCaptan

IprodioneIprodione

8.3 hrs pH 78.3 hrs pH 72 min pH 102 min pH 10< 1 hr pH 9< 1 hr pH 9

Example of Instability Example of Instability Alkaline Hydrolysis produced by high pH Alkaline Hydrolysis produced by high pH

DimethoateDimethoate

SS

(CH(CH33O)O)22 - P - S - CH - P - S - CH22CONHCHCONHCH33

S S

(CH(CH33O)O)22 - P - OH + H - S - CH - P - OH + H - S - CH22CONHCHCONHCH33

At high (alkaline) pH, At high (alkaline) pH,

OH OH_ _

ions attack the ions attack the molecule here molecule here

Molecules that are inactive as insecticidesMolecules that are inactive as insecticides

ProducingProducing

ChlorpyrifosChlorpyrifos

S NS N

(CH(CH33O)O)22 - P - O Cl - P - O Cl

Cl Cl Cl Cl

N N S OH Cl S OH Cl

(CH(CH33O)O)22 - P - OH + Cl Cl - P - OH + Cl Cl

At high (alkaline) pH, At high (alkaline) pH,

OH OH_ _

ions attack the ions attack the molecule here molecule here

Examples of pH and StabilityExamples of pH and Stability

HerbicidesHerbicidesClodinafopClodinafopDiclofopDiclofopFlumicloracFlumiclorac

Half-LifeHalf-Life2.5 hrs pH 92.5 hrs pH 9 12 hrs pH 912 hrs pH 9 6 min pH 96 min pH 9

pH also affects the Ohio group of pH also affects the Ohio group of herbicidesherbicides

Weak Acids - OH

Examples of Weak-Acid HerbicidesExamples of Weak-Acid Herbicides

Clethodim (Select)Clethodim (Select)

Clopyralid (Curtail)Clopyralid (Curtail)

Dicamba (Banvel, Clarity)Dicamba (Banvel, Clarity)EndothalEndothal

Fluazifop (Fusilade) Fluazifop (Fusilade)

Glyphosate (Round Up, Accord, Ranger, Glyphos)Glyphosate (Round Up, Accord, Ranger, Glyphos)

Imazamox (Raptor)Imazamox (Raptor)

Imazapyr (Arsenal)Imazapyr (Arsenal)

Imazethapyr (Pursuit)Imazethapyr (Pursuit)

MCPA Amine MCPA Amine

Metsulfuron-Methyl (Ally, Escort)Metsulfuron-Methyl (Ally, Escort)

ParaquatParaquat

Picloram (Tordon) Picloram (Tordon)

Sethoxydim (Poast)Sethoxydim (Poast)

2,4-D Amine2,4-D Amine

Dissociation of a Herbicide Dissociation of a Herbicide Molecule to an ionic form at Molecule to an ionic form at

Alkaline pHAlkaline pH Picloram (Tordon)Picloram (Tordon)

At low pHAt low pH At high pHAt high pH

Neutral Molecule Ionic Molecule Neutral Molecule Ionic Molecule

CLCL

CLCL CLCLNHNH22

NN

OO

C-OHC-OH

OO

C-OC-O__NN

CLCL

CLCL CLCLNHNH22


Alkaline pHAlkaline pH 2,4 - D2,4 - D

At low pHAt low pH At high pHAt high pH

Neutral Molecule Ionic MoleculeNeutral Molecule Ionic Molecule

CLCL

CLCL

CLCL OO

OCHOCH22C-OC-O__

OO

OCHOCH22C-OHC-OH

CLCL

CLCL


Alkaline pHAlkaline pH

CL

The effect of pH on Weak-Acid The effect of pH on Weak-Acid herbicidesherbicides

Want: Neutral or uncharged whole molecule Want: Neutral or uncharged whole molecule

Don’t want: Charged or Ionic form Don’t want: Charged or Ionic form

Movement of Ionizable (Weak-Acid) Movement of Ionizable (Weak-Acid) HerbicidesHerbicides

Vascular BundleVascular Bundle

Weak-Acid herbicides in an acid environment are not ionized and Weak-Acid herbicides in an acid environment are not ionized and can freely cross plant membranes, upon entering the alkaline can freely cross plant membranes, upon entering the alkaline phloem (high pH) they will become ionized. This “traps” the phloem (high pH) they will become ionized. This “traps” the pesticide in the phloem and will subsequently be transported to pesticide in the phloem and will subsequently be transported to “active sites” within the plant.“active sites” within the plant.

Non-ionized pesticides freelyNon-ionized pesticides freelycross plant membranescross plant membranes

pH 5 Xylem 150 cm / hrpH 5 Xylem 150 cm / hr

Phloem – 90 cm / hrPhloem – 90 cm / hr pH 8 pH 8

RootsRoots

LeavesLeaves


Movement of Non-Ionized HerbicidesMovement of Non-Ionized Herbicides

Vascular BundleVascular Bundle

Once inside the plant, Once inside the plant, Non-Ionized herbicides such as atrazine can Non-Ionized herbicides such as atrazine can move freely between xylem and phloem, the xylem moves more move freely between xylem and phloem, the xylem moves more rapidly than the phloem so the net movement israpidly than the phloem so the net movement is in the direction of in the direction of xylem.xylem.


Xylem 150 cm / hrXylem 150 cm / hr

Phloem – 90 cm / hrPhloem – 90 cm / hr

StartStart

RootsRoots

LeavesLeaves

Source: NufarmSource: Nufarm

Another Point To PonderAnother Point To Ponder

The leaf surfaces of several weed species are The leaf surfaces of several weed species are alkaline (high pH)alkaline (high pH)

Causes dissociation of weak-acid herbicides Causes dissociation of weak-acid herbicides resulting in reduced uptakeresulting in reduced uptake

The condition is generally limited to broadleaf The condition is generally limited to broadleaf weedsweeds

Surface pH of Weed LeavesSurface pH of Weed Leaves

Dicotyledons Dicotyledons

VelvetleafVelvetleafRedroot PigweedRedroot PigweedCatchweed BedstrawCatchweed BedstrawTall MorninggloryTall MorninggloryPale SmartweedPale SmartweedCommon GroundselCommon GroundselTeaweed (Prickly Sida)Teaweed (Prickly Sida)Wild MustardWild MustardBlack NightshadeBlack Nightshade

MonocotyledonsMonocotyledons

8.5 - 8.758.5 - 8.758.1 - 8.28.1 - 8.27.6 - 7.757.6 - 7.758.0 - 8.28.0 - 8.27.5 - 7.67.5 - 7.67.75 - 7.87.75 - 7.88.3 - 8.68.3 - 8.68.48.48.28.2

(most are nearly (most are nearly neutral at pH 7.0)neutral at pH 7.0)

Management of Leaf Surface pHManagement of Leaf Surface pH

High leaf surface pH can be managed by High leaf surface pH can be managed by utilizing spray solutions that have been utilizing spray solutions that have been acidified. Acidified spray solutions can easily acidified. Acidified spray solutions can easily and effectively neutralize or even lower the pH and effectively neutralize or even lower the pH level.level.

Elements of the Management Elements of the Management of Water / Spray Solution pHof Water / Spray Solution pH

• Know the water pHKnow the water pH

• Know the susceptibility of pesticideKnow the susceptibility of pesticide

• Use acidifiers or adjuvants with acidification Use acidifiers or adjuvants with acidification

properties to adjust the pH level. Know that properties to adjust the pH level. Know that

some things (copper containing fungicides) some things (copper containing fungicides)

should should NOTNOT be acidified. be acidified.

• Sulfonyl ureas??Sulfonyl ureas??

Hard WaterHard Water

CaCa++++, Mg, Mg++++, Zn, Zn++++

NNAA++, K , K ++, Mn , Mn ++

Fe Fe ++++, Fe , Fe ++++++, Al , Al ++++++

Antagonistic Effects of Hard Water Antagonistic Effects of Hard Water on Glyphosate Moleculeson Glyphosate Molecules

Sodium Sodium and and PotassiumPotassium = (least effect) = (least effect)

CalciumCalcium, , ironiron, , magnesiummagnesium and and coppercopper have most effect have most effect

Glyphosate and the cations will form a strong complex which Glyphosate and the cations will form a strong complex which is physically large. This can prevent or hinder uptake of the is physically large. This can prevent or hinder uptake of the herbicide into the plant, effectively reducing herbicide herbicide into the plant, effectively reducing herbicide activity.activity.

O P - CHO P - CH22 NH NH22 CH CH22 C C ----OO

--OO

++OO

OO

OO

O P - CHO P - CH22 NH NH22 CH CH22 C C

CaCa++++,,

MgMg++++,,

The Effect of Calcium on The Effect of Calcium on Herbicide uptake by Herbicide uptake by

SetariaSetaria faberifaberi

Untreated Glyphosate(no Calcium)

Glyphosate+ CaCl2

Nicosulfuron (no Calcium)

Nicosulfuron+ CaCl2

Dirt and other stuffDirt and other stuff

Dust: Dust: Reduces the wettability and coverage of Reduces the wettability and coverage of applied spray.applied spray.

Mineral composition of dust may antagonize Mineral composition of dust may antagonize some some herbicides.herbicides.

Organic matter may bind to some herbicides.Organic matter may bind to some herbicides.Clay constituency can neutralize some Clay constituency can neutralize some

herbicides.herbicides.

Exudates: Some weeds called Halophytes (Velvetleaf Exudates: Some weeds called Halophytes (Velvetleaf and and Lambsquarter) have salt or chalk glands Lambsquarter) have salt or chalk glands which which exude calcium deposits onto the surface.exude calcium deposits onto the surface.

Water Conditioning Strategies to Prevent Water Conditioning Strategies to Prevent Antagonism of Weak-Acid herbicidesAntagonism of Weak-Acid herbicides

Removal of antagonistic ions by Removal of antagonistic ions by Ammonium SulfateAmmonium Sulfate

ConditioningConditioning

AcidificationAcidification to reduce the number of negatively to reduce the number of negatively charged herbicide ions, or to select for the ionic charged herbicide ions, or to select for the ionic charge with the least potential for antagonism. charge with the least potential for antagonism.

The Pesticide Application ProcessThe Pesticide Application Process

The Spray SolutionThe Spray Solution

AtomizationAtomization

Transport to TargetTransport to Target

Impaction / DepositionImpaction / Deposition

Post-Impact Drop Behavior Post-Impact Drop Behavior Spreading, Retention, Penetration, TranslocationSpreading, Retention, Penetration, Translocation

Biological EffectBiological Effect

Contact ActionContact Action Systemic ActionSystemic Action

Spray Drift

Documents

Effective Pesticide Application Reeves Petroff Pesticide Education Specialist MSU Extension