Pesticides in the EnvironmentEnvironmental Fate

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What is Pesticide Environmental Fate?How and where a pesticide enters the environmentHow long it lastsWhere it goes.

Pesticide Losses at ApplicationMethod of application

55%45% Rate Timing Number of applications Placement

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Pesticide CharacteristicsChemical characteristics determines behaviorFour main characteristics:SolubilityAdsorptionHalf-life (aka. Persistence)Volatility

SolubilityAmount of chemical that can be dissolved into a solution Parts per million (PPM)> 30 ppm = high tendency to leach or runoff.

Tordon = 400- 4302,4-D = 890Assert = 1370Ally/Escort1750 (pH 5) 2790 (pH 7)213,00 (pH 9) Paraquat = 7000Roundup = 12,000

Runoff vs. Leaching

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

Measuring Adsorptivity - Kocorganic carbon partition coefficient - universal indexhow tightly a pesticide will bind to the organic matter in the soil.

Adsorptivity and SolubilityLess water-soluble pesticides More adsorbedLess likely to leach or runoff

Koc of Common PesticidesBanvel 2Stinger 6Pursuit 10Tordon 162,4-D 20Assert 35 to 662,4-D Ester 100MCPA 110Broadstrike - 700

Methyl Parathion 5100Lorsban - 6070Treflan 7000Roundup 24,000Buctril 10,000Capture 216,500Paraquat 1,000,000

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

Solubility & AdsorptionSome things to ponderRead 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!

Persistence (Residual)DegradationMicrobes (#1)pH (#2)SunlightRate appliedDegraded over time to produce CO2, H2O, N, P, Su, Expressed as half-life.Time required for that substance to degrade to one-half its previous concentration.

Degradation values of some common pesticides (1/2 life in days)Malathion - 1 2,4-D - 10Banvel 14Ally, Amber 30 Stinger - 40Assert 45Roundup - 47Tordon 180 Spike - 360Paraquat 1000

Pesticide DriftPhysical drift caused by small dropletsImproper nozzlesImproper pressureChemical driftVolatilization

Comparison of Micron Sizes(approximate)2000 m850 m420 m300 m150 m100 m#2 Pencil leadpaper clipstapletoothbrush bristlesewing threadhuman hair

Driftability of Spray Droplets of Varying Sizes 10 feet Crosswind @ 3 mph 20 m 50 m100 m150 m m 8 ft 22 ft. 48 ft. 178 ft. 1065 ft.

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Nozzle Drop Size ClassesVery Fine to Fine < 200 umMedium to Coarse 200 to 450 umVery Coarse > 450 um

Tip Spray Selection by Drop SizeTurbo TeeJet Flat-fan

Evaporation of DropletsWindHigh Relative HumidityLow TemperatureLow Relative HumidityHigh TemperatureFall Distance

Evaporation and Deceleration of Various Size Droplets*DropletDiameter(microns)TerminalVelocity(ft/sec)Final Dropdiameter(microns)Time toevaporate(sec)Decelerationdistance(in)20.0470.3

Strategies to Reduce DriftAvoid adverse weather conditionsConsider using buffer zonesConsider using new technologies:drift reduction nozzlesdrift reduction additivesshields, electrostatics, air-assist Increase drop size Increase flow rates - higher application volumes Use lower pressures Use lower spray (boom) heights

Turbo Drop NozzleGreenleaf TechnologiesAir Induction (AI)Venturi pressure reduction chamberDroplets are filled with air and expand when leaving tipBetter coverage$10.00

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

VolatilityConversion of a liquid or solid to a gasLower vapor pressure = lower volatility2,4-D ester = 13 mPaBanvel = 4.5 mPaBanvel SGF = 1.6 mPaTordon = 0.082 mPaRoundup = 0.010 mPa

Volatility is also affected by:WeatherHigh temperatures2x more 2,4-D ester volatilizes at 80o than 70oLow humidity = more volatilizationAir Inversions

Protecting Water Resources

Protect your wells!

Protecting Water ResourcesPractice IPMEnvironmental considerationsWell Locations?Calibrate and use only what is neededMix and load carefullyPrevent back-siphoningConsider the weatherSelect, store and dispose of pesticides carefully

This slide represents an example of the choices an applicator would have within a single nozzle type. If the label suggested a medium sized spray droplet and the applicator wanted to use the specific nozzle type shown, then all the light blue areas in this particular chart would represent a proper selection. This would allow for maximum flexibility as application conditions changed form day to day and even during the day. As an example, as wind speed increased, or the temperature increased and humidity dropped, choosing to operate at a lower pressure making bigger drops should minimize the drift potential.These nozzles were originally manufactured in Germany by Agrotop Company and distributed in the US by Greanleaf Technologies (Covington, Louisiana). The TurboDrop nozzles are designed to produce larger droplets while reducing the percentage of fine droplets. As with other low-drift nozzles, TurboDrop nozzles have a pre-orifice ahead of the exit orifice to reduce the pressure exerted on the liquid at the point of discharge (Figure 4). The lower part of this nozzle represents a typical standard flat- fan nozzle set up. The top part of the nozzle contains a pressure reduction chamber with a narrow port used to draw air into this pressure chamber. The flow rate is controlled by a ceramic orifice plate located at the bottom of the first section. As the liquid passes through the orifice plate, as a result of the pressure drop created by this venturi, air is sucked into the nozzle body. In the mixing chamber, air and spray solutions are blended much like a water aspirator. As the liquid is discharged from the nozzle tip, droplets filled with air are produced. The exit nozzle does not control the output rate, but rather forms the desired pattern. Therefore, a standard flat-fan tip with a larger orifice can be used to produce larger droplets. Upon leaving the nozzle orifice, the air included in the nozzle expands, which makes the size of droplets somewhat larger and causes an increase in velocity of droplets. In addition to the large droplets, having a higher velocity on the nozzles further improves the chances the droplet will reach the target before becoming subject to drift. Another benefit mentioned by the manufacturers of this nozzle is that the large droplets shatter and splatter on contact, causing the small air-filled drops to spread out on the target for better coverage. According to its manufacturers, TurboDrop reduces the drift of small droplets considerably.