Characteristics of Pesticides Basic concepts relating to the names, chemistry, behavior and fate of...
Transcript of Characteristics of Pesticides Basic concepts relating to the names, chemistry, behavior and fate of...
Characteristics of Pesticides
Basic concepts relating to the names, chemistry, behavior and fate of Pesticides including a review of the R8 Label Book summary pages
Pesticide Names
Chemical name *
Common name *
Product name *
There are three names associated with every pesticide
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definitions
Pesticide Names:Chemical Name
The systematic Name of a Chemical Compound according to the rules of nomenclature of the International Union of Pure and Applied Chemistry as adapted for indexing in Chemical Abstracts
For example: 3,5,6-trichloro-2-pyridinyloxyacetic acid.. is a chemical name
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Pesticide Names:Common Name
A generic name for a chemical compound (see the Weed Science Society of America list of herbicide nomenclature)
For example: The common name for 3,5,6-trichloro-2-pyridinoxyacetic acid.. is triclopyr
The common name is the name generally used in discussing pesticidal toxicology and environmental behavior and fate
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Pesticide Names:Product Name
The trade name of a pesticide; that is the name on the container you purchase. It is also the name to which the EPA registration number is applied at the time of registration
Triclopyr alone is sold as: Garlon 3A or Garlon 4
Names in the R8 Label BookSummary Sheets
• Common names
• Brand names
• (If the chemical name is needed – see the label not the summary sheet)
Another Caution ---Pronunciation of Names
FORAY
4-AA
PHORATE
Some quick definitions
Solution *
Suspension *
- Emulsion *
- Invert Emulsion *
Bypass definitions
Some quick definitions
Solution
A liquid or solid chemical which is dispersed completely (not suspended) in water or another fluid. For our purposes this includes water solutions and ester or other oil-soluble chemical dissolved in oil
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Some quick definitions
Suspension
Finely divided solid particles or liquid droplets dispersed (but not dissolved) in another solid, a liquid or a gas.
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Some quick definitions
Emulsion
A suspension of small droplets of an oil-based or an ester pesticide in water
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Some quick definitions
Invert Emulsion
A suspension of small droplets of water in an oil. Some chemicals are now produced as invert emulsions
Some quick definitions
Invert Emulsion
Generally the formation of an invert emulsions is undesirable. Without special precautions during mixing and use they commonly form resulting, in a sludge of the approximate consistency of mayonnaise that clogs hoses and nozzles and creates a major problem of clean-up
Some quick definitions
Solution Suspension
Emulsion Invert emulsion
Oil droplets in water
Water droplets in oil
Dissolved –Does not separate
Mixed – can
separate
Types of Product Formulation
• Liquids– Solutions– Emulsifiable
concentrates– Ultra Low Volume
Concentrates– Low Volume
Concentrates– Aerosols– Liquified gas
• Solids– Dusts– Granules– Pellets– Soluble Powders– Wettable Powders– Flowables– Baits
Gross Classification of Pesticides by Chemistry
• Inorganic pesticides *
• Organic pesticides *
• Biological pesticides *
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Gross Classification of Pesticides by Chemistry
• Inorganics – Molecules do not contain carbon
• Heavy metals – lead and arsenic• Copper products• Sulfur products
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Gross Classification of Pesticides by Chemistry
• Organics – Molecules contain carbon
• May be chains or rings
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Gross Classification of Pesticides by Chemistry
• Biologicals– Viruses, bacteria, fungi, and plants– Nematodes, insects and other parasites or
predators
Classification of Organic Herbicides by Chemistry
• Phenoxy herbicides *
• Triazines *
• Imidazolinone *
• Sulfonylureas *
Bypass details
Classification of Organic Herbicides by Chemistry
• Phenoxy herbicides – 2,4-D, 2,4-DP, 2,4,5-T– Behaves as an auxin causing hypertrophy– Sample structure
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Classification of Organic Herbicides by Chemistry
• Triazines – Hexazinone– Have extreme soil
mobility– Structure
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Classification of Organic Herbicides by Chemistry
• Imidazolinone – Imazapyr
– Structure
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Classification of Organic Herbicides by Chemistry
• Sulfonylureas – Metsulfuron & sulfometuron methyl– Sample structure
Classification of Organic Insecticides by Chemistry
• Chlorinated hydrocarbons *
• Organophosphates *
• Carbamates *
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Classification of Organic Insecticides by Chemistry
• Chlorinated hydrocarbons – Dieldrin, aldrin, DDT, mirex, chlordane– Sample structure
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Classification of Organic Insecticides by Chemistry
• Organophosphates – Malathion, azinphos-methyl, naled– Sample structure
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Classification of Organic Insecticides by Chemistry
• Carbamates – Carbaryl (Sevin)– Structure
2 Basic Chemical Groups for Herbicides
Amines *
Esters *
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AmineGeneral Characteristics
• Organic salt• Water soluble• Low volatility• Low in its toxicity to fish• Used for injection & cut-surface
treatments
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Esters(General Characteristics)
• Oil based
• Oil soluble / can be emulsified in water
• Generally highly volatile
• Highly toxic to fish
• Used for bark & foliar applications
Amine Ester
• Organic salt • Oil based
Injection & cut-surface treatments
Low toxicity for fish
Low volatility
Water soluble
Bark or foliar applications
High toxicity for fish
High volatility
Oil soluble or can be emulsified in water
LD50s of field formulations
Garlon 4 --LD50 1,419 mg/kg
Triclopyr – LD50 630 mg/kg
LD50s of field formulations
Garlon 4 --LD50 1,419 mg/kg
Streamline uses a 17% solution of Garlon 4 => 1,419 / 0.17 = 8,347 mg/kg
Foliar spray is normally done as a 3% solution => 1,419 / 0.03 = 47,300 mg/kg
Environmental behavior:Several categories of environmental
behavior are included in the summaries which precede each chemical presented in the Region-8 Label Book
Information includes:
• Mode of action• Selectivity• Soil activity and mobility• Persistence and
breakdown
• Toxicity to humans and wildlife
• Application timing• Weaknesses or
limitations
The following slides discuss these and several other properties of pesticides in general
Discussion in the “R-8 Label Book” section (later this week) presents chemical specific information
Mode of Action:Herbicides
• Movement in the plant– Contact *– Translocated *
• Action in the plant– Inhibit protein synthesis, photosynthesis, or growth
Bypass definitions
Mode of Action:Contact Herbicide
One which causes injury to only the plant tissue to which it is applied, or one which is not appreciably translocated within a plant
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Mode of Action:Translocated Herbicide
One which is moved within a plant from the point of application to the point of action; may be either phloem-mobile or xylem-mobile
The term is often misapplied to include only foliar applied herbicides which move downward from the leaves to the roots
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Mode of Action: Animal Poisons (incl. Insecticides)
Contact poison *
Systemic poison *
Attractants * Pheromones Baits
Repellants * Bypass definitions
Mode of Action:Contact Insecticide
Pesticide which causes injury or death of insect through the touch rather than
through inhalation or ingestion
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Mode of Action:Systemic Insecticide
Pesticide which is moved within a plant from the point of application to the point where the insect will contact or ingest it
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Mode of Action:Attractants
Pesticide which lures animals to a predetermined spot– Pheromones are biochemicals either released by
the animal or synthesized which are sex attractants – Baits are chemicals which entice animals for
reasons other than sex (smells like food)
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Mode of Action:Repellants
Pesticide which discourages animals from coming to a specific area
– Many chemicals unrelated to sexual activity (due to smell or other physical characteristic) are repellant to animals
– Pheromones in low concentration are attractive to animals but, often, in high concentration become repellant
Mode of Action:Life Stage Affected
Ovicide *
Larvicide *
Adulticide *
Bypass
Definitions
Mode of Action:Life Stage Affected
Ovicide
– Kills eggs
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Mode of Action:Life Stage Affected
Larvicide
– Kills larval stage (immature) insects
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Mode of Action:Life Stage Affected
Adulticide
– Kills adult insects
Mode of Action:Selectivity
• Many products express a degree of selectivity – Extremely variable from product to product– Biologicals often more selective than chemicals
• Despite claims, selectivity is generally limited– Often based on rate
• Many newer products are more selective• Application method also influences selectivity
Soil Activity
Soil Active Herbicide: applied to or present in the soil, these chemicals are readily absorbed by plant roots and subsequently negatively affects the plant in some manner
Soil Activity
Non Soil Active Herbicide: applied to or present in the soil, these chemicals are bound to soil particles or organic matter and are essentially unavailable to affect plants
Soil Mobility
• A major contributor to offsite movement• Leaching vs. lateral movement• Affected by the soil’s
– Sand content– Clay content– Organic matter content
• Affects chemical half-life but not the degradation
Persistence and Degradation
• Persistence – The resistance of a herbicide to metabolic or environmental degradation or removal; a measure of the duration of retention of activity by a pesticide in the environment
Degradation – The breakdown of a substance into simpler molecular or atomic components through chemical reaction(s) either in a plant or animal (metabolic degradation) or in the environment (environmental degradation)
Persistence/Degradation:Process Drivers
• Temperature• Relative humidity / Rainfall• pH• Insolation• Soil or water biota
– Macrophytes– Microbial populations– Worms and microfauna
Persistence and Degradation: Half-Life
The time required for half the amount of a substance (such as a herbicide) present in or introduced into a system (living or ecological)
to be eliminated, whether by excretion, metabolic degradation, off-site transport, or
other natural process
Toxicity to Humans and Wildlife
• Varies by chemical
• Based on the target biochemistry of the product
• Much more later in this session
Primary Forestry Uses
• Discussion of silvicultural and other uses
• And, of methods of application
• Appropriate for the formulation(s) of the pesticide available for use
• Much more later
Application timing
• Product specific
• May also relate to formulation
• Gives a measure of selectivity
• Discussed for each pesticide and formulation
• Summarized in the Label Book in a comparative table for all herbicides
Weaknesses and Limitations
• Repeats environmental concerns
• Toxicological/health concerns
• Lists formulation specific concerns such as flammability
• Lists use restrictions
Environmental behavior:
More thoughts not in specific categories in the label book
Off-site movement
Lots of differing processes involved
Pesticide Movement & Degrade
• Runoff *• Leaching *• Degradation
– Microbial *– Physical
– Hydrolysis *– Photolysis *– Pyrolysis *
• Volatilization *Bypass
definitions
Pesticide Movement & Degrade
• Runoff – movement of pesticide aboveground in water –
generally occurs downslope but can also occur on flat or even slightly uphill ground after a flloding rain
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Pesticide Movement & Degrade
• Leaching– Also called percolation – the process whereby pesticide is
moved down through the soil profile
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Pesticide Movement & Degrade
• Microbial Degradation– Breakdown of pesticides by fungi, bacteria and other
microscopic organisms
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Pesticide Movement & Degrade
• Physical Degradation– Hydrolysis -- Breakdown of a
pesticide by water
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Pesticide Movement & Degrade
• Physical Degradation– Photolysis – breakdown of a pesticide by
sun or other light
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Pesticide Movement & Degrade
• Physical Degradation– Pyrolysis – the breakdown
of a pesticide by heat or fire
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Pesticide Movement & Degrade
• Volatilization – evaporation of a heated pesticide
Breakdown generalizations
• Hotter temperature = faster breakdown
• Higher relative humidity = faster breakdown
• More microbes = faster breakdown
• pH effect = chemical dependant
• More slope = more runoff
Off-site movement generalizations
• More clay and organics = less leaching• Higher temperature = more volatilization• Lower relative humidity = more volatilization• Higher wind speed = more volatilization and
drift• Nearer to moving water = higher probability of
contamination and off-site movement• Finer droplets = more movement