Reeves PetroffMSU Extension

Pesticide Education Specialist

http://

mtpesticides.orghttp://

mtpesticides.orgKnowledge, Information &

Links

How water quality

affects certain pesticides

•Minerals •pH•Dirty Water

Goal

How water quality

affects certain pesticides

•Weak acid herbicides•Insecticides

–Organophosphates–Carbamates

Goal

O-

H+

H+

O-

H+

H+

- Covalent Bonds – shared electrons

pH of 7 = neutral

-Universal Solvent – Dissolves & attracts many substances

Hydrological CycleAdds minerals and pH to water

CO2 + H20 = carbonic acid

Minerals

Bicarbonate HCO3

Alkaline

Carbonate CO3

Alkaline

WaterPrimary diluent

Why water quality is important!

• 1 pint or 1 quart per acre

• 30 GPA application volume

• 99% and 93% of spray solution

New Term

Minerals

Hard WaterHard Water

Total Dissolved Solids

TDS

ppm

grains* 17 ppm per grain

Common mineral elements in Montana water

Positive Charge (cations) Negative Charge (anions)

Calcium (Ca++) Sulphate (SO4-)

Magnesium (Mg++) Chloride (Cl -)

Sodium (Na+) Bicarbonate (HCO3-)

nitrate (NO3-)

potassium (K+) iron (Fe++, Fe+++),

Ions - Charged atoms

ppm/Gal Grains/Gal

Soft 0 - 60 0 – 3.5

Mod. Hard 60 - 120 3.5 – 7.0

Hard 120 - 180 7.0 – 10.5

Very Hard Over 180 Over 10.5

Reference: Montana Environmental Health Association – Sanitarian’s Field Guide

What is hard water?

How is TDS measured?

• Weight

• EC

• Chemical reaction (Test Strips)

Calcium = 666 ppm

Sulphate = 2434 ppm

Magnesium = 234 ppm

Chloride = 32 ppm

Sodium = 130 ppm

Bicarbonate = 346 ppm

TDS > 500 mg/L (ppm) is salty to taste

3842 ppm.

Types Of WaterTypes Of Water Drinking water <500 TDS (EPA)Drinking water <500 TDS (EPA)

Fresh Water : <1,000 TDS Fresh Water : <1,000 TDS

Brackish : 1,000-5,000 TDS Brackish : 1,000-5,000 TDS

Highly Brackish : 5,000-15,000 Highly Brackish : 5,000-15,000 TDS TDS

Saline : 15,000-30,000 TDS Saline : 15,000-30,000 TDS

Sea Water : 30,000-40,000 TDS Sea Water : 30,000-40,000 TDS

Brine : 40,000-300,000+ TDSBrine : 40,000-300,000+ TDS

Understanding Water Hardness

Water Softening – Ion Exchange

Na+Na+ Na+

Na+

Na+

Na+

Na+Na+ Na+

Na+

Na+

Na+

• Resin Beads

• anionic (-)

• hold cations(+)

Na+

Na+

Na+

Na+

Mg++

Na+

Na+

Na+Na+ Na+

Na+

Na+

Na+

Ca++

Mg++

Mg++

Mg++

Mg++

Ca++

Ca++

Ca++Ca+

+

Ca++

Ca++

Mg++

Mg++

Flow

Water Quality Effects on Herbicides

Hard WaterHard Water

Glyphosate(Roundup)

use rate

Maximum Water Hardness

Grains/US gal.

ppm CaC03 equivalent

Low Rates for Annual Grass Weeds

20 350Higher rates for Perennial Weeds 40 700

Weak Acid Herbicides

• Acids release H+ ions in water• Weak acids release H+ slightly

Glyphosate – Roundup

Paraquat – Gramoxone

Clethodim – Select

Sethoxydim – Poast

Many 2,4-D products

• Most affected by hard water and pH

Weak Acid Herbicides

C-O-

C

C

C-CH3

CH3 |

+NH2 |

CH3

Dissociation – splitting of the molecule

Weak Acid Herbicides

C-O-

C

C

C-CH3

CH3 |

+NH2 |

CH3

+Ca

+

C-O-

C

CC-CH

3

- Herbicide molecule -

• Penetrate the target weed intact

•Travel to the site of action

• Kill the plant.

CH3 |

+NH2 |

CH3

Intact molecule = more plant penetration

C-O-

C

C

C-CH3

Water pH & Herbicides

What is pH?

• Measures H+ ions

• potential Hydrogen

• More H+ = lower pH = more acid

Logarithmic

pH and Herbicides

• Acidic conditions for most herbicides– pH 3 to 6

• Lower pH avoids dissociation

• The exceptions•Ally•Escort •Read the label

pH Hard WaterHigh pH = dissociation

Molecule is vulnerable

C-O-

C

C

C-CH3

CH3 |

+NH2 |

CH3

+Ca

+

Bicarbonate

Waters• Associated with sodium• > 500 ppm & high pH• Affects 2,4-D • Affects “dim” herbicides

• Poast - sethoxydim• Select – clethodim• Achieve -tralkoxydim

…dim herbicides

Bicarbonate Waters- Solution -

• Use maximum allowed rate• Apply during optimal growth stage• Adjuvants

- Non-ionic Surfactant (NIS) - Acidifiers/buffers

Water Quality Effects on Herbicides

TurbidityTurbidity

Total Suspende

d Solids

TSS

Total Suspende

d Solids

TSS

• diquat (Reglone, Reward)

• paraquat (Gramoxone)

• glyphosate (Roundup,

Touchdown, etc.Organic Matter

OM

Organic Matter

OM

DirtDirt

Water Quality Effects on Herbicides

• Binds the herbicide

+ + Roundup +

+

- - OM -

-

• Clogs screens

• Pumps?

Herbicide not

absorbed

TSS – Solutions

• Clean water supply

• Filtering

Settle basin

Filters

pH & Insecticides

•Organophosphates–Malathion–Parathion

•Carbamates–Sevin

Solutions? 1. Test the

water • Test strips

• Meters

• Labs

Test strips

• Easy to use

• Cheap - $8 to $20

• Some combine ph & hardness

• Improved accuracy

Meters• Accurate

• Calibrated

• $100 +

pH, EC, TDS

$179.00

www.gemplers.com

Labs • Collection guidance

• Tests performed

• How to interpret results

•$50 – $100+

http://mtpesticides.org

Links Labs

1. Test the water 2. Reduce Water Volume

• Less ions present

• Example:

25 to 15 GPA

• Only if practical

• pH still a problem

• Label?

1. Test the water 2. Reduce Water Volume

• More pesticide ions present

• More costly

• Non-target damage?

3. Use maximum allowed rate

1. Test the water 2. Reduce Water Volume

• Mix what you need

• Smaller areas

• Planning

• Scouting

• Good notes

3. Use maximum allowed rate

4. Spray ASAP after mixing

1. Test the water 2. Reduce Water Volume3. Use maximum

allowed rate

4. Spray ASAP after mixing5. Adjuvants

www.herbicide-adjuvants.com

• Additives to improve performance

Adjuvants

• Conditioners

• Ammonium Sulfate (AS)

• Non-ionic surfactants (NIS)

pH

HardWater

• Acidifiers

• Buffers