Pesticides in the Environment Environmental Fate of

What is Pesticide Environmental Fate? How and where a pesticide enters the environment How long it lasts Where it goes.

Pesticide Losses at Application Method of application 55% 45% Rate Timing Number of applications Placement

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Pesticide Characteristics Chemical characteristics determines behavior Four main characteristics: –Solubility –Adsorption –Half-life (aka. Persistence) –Volatility

Solubility Amount of chemical that can be dissolved into a solution Parts per million (PPM) > 30 ppm = high tendency to leach or runoff. Tordon = ,4-D = 890 Assert = 1370 Ally/Escort –1750 (pH 5) – 2790 (pH 7) –213,00 (pH 9) Paraquat = 7000 Roundup = 12,000

Runoff vs. Leaching

Adsorption Binding Organic matter More organic matter = more binding by less- soluble pesticides

Measuring Adsorptivity - K oc organic carbon partition coefficient - universal index how tightly a pesticide will bind to the organic matter in the soil.

Adsorptivity and Solubility Less water-soluble pesticides More adsorbed Less likely to leach or runoff

K oc of Common Pesticides Banvel – 2 Stinger – 6 Pursuit – 10 Tordon – 16 2,4-D – 20 Assert – 35 to 66 2,4-D Ester – 100 MCPA – 110 Broadstrike Methyl Parathion – 5100 Lorsban Treflan – 7000 Roundup – 24,000 Buctril – 10,000 Capture – 216,500 Paraquat – 1,000,000

Generally, solubility and adsorption are inversely related As solubility increases; absorption decreases Always the exception: Roundup and paraquat. Both are highly water soluble but bind very tightly to soil.

Solubility & Adsorption Some things to ponder Read the label! –Look for restrictions based on soil type. Example – Tordon restriction on loamy sand to sandy soils. Calibrate! Calibrate! Calibrate! Do not over apply Know the soil type in the area you are spraying. Conduct a soil test….

Texturing your soils

Even a jar test will give you an idea!

Degradation –Microbes (#1) –pH (#2) –Sunlight –Rate applied Degraded over time to produce CO 2, H 2 O, N, P, Su, Expressed as “half-life.” Time required for that substance to degrade to one-half its previous concentration. Persistence (Residual)

Malathion - 1 2,4-D - 10 Banvel – 14 Ally, Amber – 30 Stinger - 40 Assert – 45 Roundup - 47 Tordon – 180 Spike Paraquat – 1000 Degradation values of some common pesticides (1/2 life in days)

Pesticide Drift Physical drift caused by small droplets –Improper nozzles –Improper pressure Chemical drift –Volatilization

Comparison of Micron Sizes (approximate) 2000  m 850  m 420  m 300  m 150  m 100  m #2 Pencil lead paper clip staple toothbrush bristle sewing thread human hair

Driftability of Spray Droplets of Varying Sizes 10 feet 3 mph 20  20  50  50  100  150   8 ft 22 ft. 48 ft. 178 ft ft. 8 ft 22 ft. 48 ft. 178 ft ft. \

Nozzle Drop Size Classes Very Fine to Fine < 200 um Medium to Coarse – 200 to 450 um Very Coarse > 450 um

Tip Spray Selection by Drop Size Turbo TeeJet Flat-fan

Evaporation of Droplets Wind High Relative Humidity Low Temperature Low Relative Humidity High Temperature Fall Distance

Evaporation and Deceleration of Various Size Droplets* Droplet Diameter (microns) Terminal Velocity (ft/sec) Final Drop diameter (microns) Time to evaporate (sec) Deceleration distance (in) < *Conditions assumed: 90 F, 36% R.H., 25 psi., 3.75% pesticide solution

Strategies to Reduce Drift Avoid adverse weather conditions Consider using buffer zones Consider using new technologies: –drift reduction nozzles –drift reduction additives –shields, electrostatics, air-assist Increase drop size Increase flow rates - higher application volumes Use lower pressures Use lower spray (boom) heights

Turbo Drop Nozzle Greenleaf Technologies Air Induction (AI) Venturi pressure reduction chamber Droplets are filled with air and expand when leaving tip Better coverage $10.00

LI 700 R-11 Tallow Amine Water Adjuvant Influence on Spray Pattern (Note Uniformity of Pattern) Source: FRI New Zealand

Volatility Conversion of a liquid or solid to a gas Lower vapor pressure = lower volatility 2,4-D ester = 13 mPa Banvel = 4.5 mPa Banvel SGF = 1.6 mPa Tordon = mPa Roundup = mPa

Volatility is also affected by: Weather –High temperatures 2x more 2,4-D ester volatilizes at 80 o than 70 o –Low humidity = more volatilization –Air Inversions

Protecting Water Resources

Protect your wells!

Protecting Water Resources Practice IPM Environmental considerations Well Locations? Calibrate and use only what is needed Mix and load carefully Prevent back-siphoning Consider the weather Select, store and dispose of pesticides carefully