Presentation on theme: "Environmental Fate of Herbicides and Environmental Impacts Cecil Tharp Montana State University Pesticide Safety Education Program."— Presentation transcript:
Environmental Fate of Herbicides and Environmental Impacts Cecil Tharp Montana State University Pesticide Safety Education Program
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
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?
How does a pesticide move and degrade? Pesticide characteristics Soil Factors Other Environmental Conditions Pesticide Spills?
27% of Montana applicators surveyed indicated they did not clean up all pesticide spills during their spray career.
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
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
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
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
Understand your soil texture related to the adsorption of your pesticide
Types of Soil Texture & Adsorption / Infiltration
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
Pesticide Persistence in Soils Low Persistence (half-life <30 days) Moderate Persistence (half- life 30-100 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
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
What is pH? Is the measure of the concentration of hydrogen ions (H+) and hydroxide ions (OH-) in a solution. Scale is logarithmic from 0 - 14 Hydrogen predominates (acidic < 7) Hydroxide predominates (alkaline > 7)
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
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
Drift depends on: Wind speed Droplet size from nozzles Spray tip height Temperature Volatility of pesticide
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.