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Environmental Fate of Herbicides and Environmental Impacts Cecil Tharp Montana State University Pesticide Safety Education Program.

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Presentation on theme: "Environmental Fate of Herbicides and Environmental Impacts Cecil Tharp Montana State University Pesticide Safety Education Program."— Presentation transcript:

1 Environmental Fate of Herbicides and Environmental Impacts Cecil Tharp Montana State University Pesticide Safety Education Program

2 How does this relate to us?  Many non-target plants are vulnerable to pesticide movement off-site. Gardens, Ornamentals  We drink and use well water 50% of Montana Citizens drink well water 95% of those living in agricultural communities  Restricted Use Applicators of Major Concern

3 Judith River Basin Project  33 different pesticides detected  SU’s (83 detects) Metsulfuron methyl, chlorsulfuron, prosulfuron, flucarbazone, triasulfuron, sulfosulfuran, MCPP, MCPA High of chlorsulfuron  Atrazine (15 detects)  Picloram  2,4-D  Why?

4 How does a pesticide move and degrade?  Pesticide characteristics  Soil Factors  Other Environmental Conditions  Pesticide Spills?

5 27% of Montana applicators surveyed indicated they did not clean up all pesticide spills during their spray career.

6 Mixing/Loading Sites

7 Clean up your pesticide spills  Have a pesticide spill kit Depends on site At minimum Shovel Bags Product label Paper Towels Maybe Activated charcoal 5 gallon buckets

8 Understand your environment related to the 1 st pesticide characteristic ‘solubility’!  Precipitation following your spray activity increases movement off-site.  Shallow ground water risk  Solubility of various pesticides Glyphosate - 900,000 mg / l Chlorsulfuron 7,000 mg / l Picloram – 200,000 mg / l Carbaryl – 120 mg / l

9 Understanding your pesticides characteristics – #2  Adsorption Process whereby a pesticide binds to soil particles. Occurs because of an attraction between the chemical and soil particles. Oil soluble pesticides usually bind more Water soluble pesticides bind less to soil

10 Sorption Potential (KOC) of Various Active Ingredients  Glyphosate – 24,000  Trifluralin – 8,000  Dicamba – 2  Picloram - 16  2,4-D dimethylamine salt – 20  Chlorsulfuron – 40  Atrazine - 100

11 Understand your soil texture related to the adsorption of your pesticide

12 Types of Soil Texture & Adsorption / Infiltration

13 Understanding your pesticides characteristics: #3  Persistence The ability of a pesticide to remain present and active in its original form for an extended period prior to breaking down. Based on a pesticides ½ life. Ex. Does not break down  present at wrong sites

14 Pesticide Persistence in Soils Low Persistence (half-life <30 days) Moderate Persistence (half- life days) High Persistence (half-life >100 days) AldicarbAldrinBromacil CaptanAtrazineChlordane DalaponCarbarylLindane DicambaCarbofuranParaquat MalathionChlorsulfuronPicloram Methyl ParathionEndrinTrifluralin PermethrinFonofos 2,4-DGlyphosate 2,4,5-THeptachlor Acie C. Waldron, Pesticides and Groundwater Contamination, Ohio State University Extension Bulletin 820, 1992 available at.http://ohioline.ag.ohio-state.edu/b820/index.html

15 Pesticides Persistence is Dependent on many Factors  Microbial Action - Process by which chemicals are degraded by bacteria or fungi  Photodegradation: the breakdown of chemicals by sunlight  Chemical Degradation: Hydrolysis: The breakdown of chemicals with water increases in soils with a high pH. If > 8.0 (highly alkaline)  lower the pH for better results: Use Buffercide, Bufferplus, Unifilm B, or Nutra Plus. Recommend water within a range of 4 – 7

16 What is pH?  Is the measure of the concentration of hydrogen ions (H+) and hydroxide ions (OH-) in a solution.  Scale is logarithmic from Hydrogen predominates (acidic < 7) Hydroxide predominates (alkaline > 7)

17 Dissociation from alkaline hydrolysis  Efficacy often goes down as plants don’t absorb dissociated pesticides as well. At times this may inactivate the pesticide. pH 6 – 7 ideal for most pesticides but it can vary.  Weak Acid Herbicides (pKa between -2 and 12) are the most susceptible to dissociation Lower values are more acidic Strong Acids are below -2

18 Pesticides vulnerable to abnormal pH  At pH > 7, many organophosphate, pyrethroid, or carbamate insecticides can break-down in a matter of hours or minutes  Sulfonyl urea (SU) herbicides (Escort, Ally) tend to break down more rapidly when the pH is < 6 (acid hydrolysis).  High pH can weaken some weakly acidic herbicides like Roundup® (glyphosate) Pursuit® (ammonium salt of imazethapyr) Liberty® (glufosinate ammonium). 2-4D salt

19 Overall Pesticide Movement: Leaching Potential

20 Judith River Basin Project  33 different pesticides detected  SU’s (83 detects) Metsulfuron methyl, chlorsulfuron, prosulfuron, flucarbazone, triasulfuron, sulfosulfuran, MCPP, MCPA High of chlorsulfuron 0.13 (HHS = 1,750ppb)  Atrazine (15 detects) 0.55 (HHS = 3ppb)  Why? #1 Shallow Ground Water wells < 50’ deep #2 Gravel terrace #3 Pesticide characteristics

21 What is this?

22 Drift depends on:  Wind speed  Droplet size from nozzles  Spray tip height  Temperature  Volatility of pesticide

23 Compare yourself to previous surveys across Montana.  Sixty percent of Montana applicators surveyed have sprayed when it was too windy and 1 in 5 actually caused damage to an adjacent crop? This is higher than expected. Most applicators can expect to face a difficult decision regarding spraying in a high drift situation.

24 Always Read Product Label (picloram)

25 Be aware of other environmental / non-target hazards: Precautionary Statements  Grazing Intervals  Re-crop restrictions  Pre-harvest intervals  Composting restrictions

26

27 New Chemicals on the Horizon  355 complaints of damage or injury towards trees.  A new herbicide used to manage broadleaf weeds in turf is implicated. Aminocyclopyrachlor

28 Contact Information Cecil Tharp Pesticide Education Specialist


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