1. Environmental Fate of Pesticides in the Environment

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

3. Fate Processes Adsorption Transfer Degradation

4. Fate Processes Adsorption Transfer –Volatilization –Runoff & leaching –Absorption –Crop Removal Degradation

5. Pesticide Losses at Application Method of application Rate Timing Number of applications Placement

6. Pesticide Characteristics Chemical characteristics of a pesticide will determine how it behaves in the environment. Four main characteristics: –Solubility –Adsorption –Half-life (aka. Persistence) –Volatility

7. Solubility Amount of chemical that can be dissolved into a solution Expressed as parts per million. > 30 ppm means high solubility = high tendency to leach or runoff. Tordon = 400- 430 2,4-D = 890 Assert = 1370 Ally/Escort –1750 (pH 5) – 2790 (pH 7) –213,000 (pH 9)  Paraquat = 7000 Roundup = 15,700 –900,000

8. Runoff vs. Leaching

9. Adsorption The binding of a pesticide molecule to a soil particle Mostly due to organic matter that coats the soil particle More organic matter = more binding by less-soluble pesticides

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

12. Adsorptivity Binding of a pesticides to soil particles..OM

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

14. 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 - 700 Methyl Parathion – 5100 Lorsban - 6070 Treflan – 7000 Roundup – 24,000 * Buctril – 10,000 Capture – 216,500 Paraquat – 1,000,000 * binds tight but also highly water soluble

15. Solubility & Adsorption Some things to ponder Read the label! –Look for restrictions based on soil type. Example – restrictions 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….

16. Texturing your soils

18. Even a jar test will give you an idea!

19. 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)

20. Malathion - 1 2,4-D - 10 Banvel – 14 Ally, Amber – 30 Stinger - 40 Assert – 45 Roundup - 47 Tordon – 90 to 180 Spike - 360 Paraquat – 1000 Degradation values of some common pesticides (1/2 life in days)

21. Persistence, Solubility & Adsorption – Summary

22. pH Measures the concentration of Hydrogen ions A scale for measuring acidity & alkalinity 0 - 14 pH 2 is strongly acid - batteries pH 3-4 - citrus fruits pH 5 - coffee pH 7 - neutral pH 8 – baking soda pH 9-10; soaps pH 11 - ammonia pH 13; lye

23. * At a low pH, 2,4-D is an uncharged molecule * At a high pH, 2,4-D becomes anionic or negatively charged H+ OH - O-CH 2 -C-OH O-CH 2 -C-O - OH indicates this is a weak acid. The H can be easily “pulled off” by pH effects

24. Pesticides and pH Acid dissociation - (pKa) –pH at which the pesticide degrades –If pH > pKa …degradation begins –Tells only when degradation occurs..not the rate of degradation.

25. Some common pKa’s Tordon – 2 Banvel – 2 Curtail – 2 2,4-D – 3 Roundup – 6

26. Low pH Acid Hydrolysis Sulfonyl Urea herbicides degrade in acidic environments. –Ally and Escort Most sulfonyl ureas are stable in pH > 7.9

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

28. Physical drift is a product of: droplet size that is produced by a nozzle orifice pressure produced by the sprayer that is measured in Pounds Per Square Inch (p.s.i) Weather – wind & relative humiditywind

29. Measuring Droplet Size All nozzles produce a wide range of drop sizes and not a single drop size. Volume Median Diameter” or VMD –diameter at which half the spray volume is in droplets of larger diameter and half is in smaller droplets. –If a nozzle is producing droplets of 500 microns VMD, it is producing 50% of the volume in larger drops and 50% in drops smaller than 500 microns. While 100 micron droplets are best for insects and mites, 200-500 microns is best to limit drift

30. Vapor Drift Pesticide changes from liquid or solid state in to a gas --the pesticid evaporates!! Moves from the target area 2,4-D ester & MCPA ester can produce damaging vapors readily at a given temperature Vapor pressure is just one chemical property of a pesticide that affects vapor drift.

31. Vapor Pressure Vapor pressures vary widely among pesticides. The least volatile pesticides: –salts and acids Pesticide more prone to volatize: –phenols and esters

32. Volatility Conversion of a liquid or solid to a gas Lower vapor pressure = lower volatility EPTC – 3.4 x 10 -2 mm Hg Fargo – 1.1 x 10 -4 mm Hg 2,4-D ester = 13 mPa Banvel = 4.5 mPa (9x10 -6 mm Hg) Banvel SGF = 1.6 mPa Tordon = 0.082 mPa (6x10 -7 mm Hg) Roundup = 0.010 mPa (2x10 -7 mm Hg

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

34. Protecting Water Resources

35. Protect your wells!

36. 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

39. Factors Affecting Pesticide Performance. Adjuvants and Surfactants. Reeves Petroff Pesticide Education Specialist Montana State University

40. Pesticides: Active and Inert Ingredients Active Ingredient (a.i) - Part of the pesticide that has the pesticidal properties: kill, impair, or affect. Inert Ingredients: Part of the pesticide formulation that act as emulsifiers, solvents, carriers, and surfactant and supposedly will not affect the pest if used by itself. –Some inerts may be more toxic to humans than the A.I!

41. Water Quality pH (alkalinity) Hard Water Dirty Water

42. pH Measures the concentration of Hydrogen ions A scale for measuring acidity & alkalinity 0 - 14 pH 2 is strongly acid; batteries pH 3-4; citrus fruits 7 is neutral pH 9-10; soaps pH 13; lye

43. * At a low pH, 2,4-D is an uncharged molecule * At a high pH, 2,4-D becomes anionic or negatively charged H+ OH - O-CH 2 -C-OH O-CH 2 -C-O -

44. Alkaline Hydrolysis Breakdown of pesticides due to high pH (alkalinity.) Some pesticides can breakdown into inactive parts in a matter of hours and or minutes. The ideal pH for spray solutions is slightly acidic (pH 5-7). –Always the exception: Ally & Escort (SUs) degrade in acid environments < pH 7. Stable in alkaline environments Use a buffering or acidifying adjuvant.

45. pH Effects On Commonly Used Pesticides

46. Water Hardness Hard water contains calcium, magnesium, iron Can deactivate pesticides or cause them to fall out of solution Water conditioners lower pH & tie up hard water ions Hard water ions can replace pesticide ions. 2,4-D

47. O-CH 2 -C-O - Na+ Cl Ca+ An Amine Salt of 2,4-D Calcium replaces the sodium

48. O-CH 2 -C-O - Ca+ Cl Herbicide falls out

49. O-CH 2 -C-O - N+ Cl CH 3 A diethylamine salt or ester of 2,4-D. Less susceptible to hard water ions Key Point: Be wary of sodium salts in hard water situations. Use water conditioner if necessary

50. Different 2,4-D’s & Hard Water Form of 2,4-D Stability in Hard Water* Di-ethyl amineFair K, Na salts Poor EstersGood

51. To choose the best adjuvant: Read the Label

52. Compatibility Test –Wear your PPE. –Obtain a clear, clean 1 quart jar. –Use the same diluent (usually water) & mix in same proportions as you use in the field ( 1 teaspoon = 1 quart of pesticide added to 50 gallons of water). –Add half of diluent to jar then add pesticide according to W-A-L-E plan. –Add Wettable & other powders & Water-dispersible granules –Agitate and add remaining diluent –Add the Liquid products, such as solutions, surfactants and flowables. –Add Emulsifiable concentrates last. Shake jar vigorously and feel sides of jar for heat. Check for lumps, scum and clumps

53. Practical Solutions If Water Quality Is A Concern Test your water source. Is it suitable for spraying pesticides? Reduce water volume to minimum required for good coverage & performance. Check label for volume specs. Use a pesticide that is least affected by water quality. Seek alternative water source Spray ASAP after adding the pesticide to the sprayer tank. Ammonium sulphate fertilizer (21-0-0-24) is registered for use with some glyphosate herbicides (rate: 7 lbs/27 gallons of water) to minimize the detrimental effects of hard water.

54. Questions to ask when considering a surfactant What are the environmental conditions before application? –Hot/dry? –Surfactant may help under less than ideal conditions What conditions follow an application? –Max rainfastness: esterified seed oils, organo-silicones, nitrogen surfactants –Not all surfactants have the same amount of rainfastness

55. Questions to ask when considering a surfactant What are the pest characteristics that may affect pesticide uptake? –Leaf surface, narrow or wide –Insect contact time Costs –Generally, non-ionic surfactants and crop oil concentrates are the least expensive –Nitrogen surfactants, esterified crop oils, organo silicones (most expensive)