1. Characteristics of Pesticides Basic concepts relating to the names, chemistry, mode-of-action and fate of pesticides Edited for general use by: Vincent Mannino, CED-Fort Bend

2. Pesticide Names There are three names associated with every pesticide: 1.Chemical name 2.Common name 3.Product/Trade name

3. 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

4. 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 pesticide toxicology and environmental behavior and fate

5. 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 4A

6. Caution --- Pronunciation of Names FORAY 4-AA PHORATE

7. Some quick definitions  Solution  Suspension  Emulsion  Invert Emulsion

8. 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 Example

9. Some quick definitions Suspension Finely divided solid particles or liquid droplets dispersed (but not dissolved) in another solid, a liquid or a gas.

10. Some quick definitions Emulsion A suspension of small droplets of an oil- based or an ester pesticide in water

11. Some quick definitions Invert Emulsion A suspension of small droplets of water in an oil. Some chemicals are now produced as invert emulsions

12. 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

13. Some quick definitions Solution Suspension Emulsion Invert emulsion Oil droplets in water Water droplets in oil Dissolved –Does not separate Mixed – can separate

14. Types of Product Formulations Liquids –Solutions –Emulsifiable Concentrates –Ultra Low Volume Concentrates –Low Volume Concentrates –Aerosols –Liquefied gas Solids –Dusts –Granules –Pellets –Soluble Powders –Wettable Powders –Flowables –Baits

15. Gross Classification of Pesticides by Chemistry Inorganic pesticides Organic pesticides Biological pesticides

16. Gross Classification of Pesticides by Chemistry Inorganics –Molecules that do not contain carbon Heavy metals – lead and arsenic Copper products Sulfur products

17. Gross Classification of Pesticides by Chemistry Organics –Molecules contain carbon May be chains or rings Carbon containing molecules are broken down by micro-organisms Organics included botanicals and man-made chemical formulations that include carbon compounds

18. Gross Classification of Pesticides by Chemistry Biologicals –Viruses, bacteria, fungi, and plants –Nematodes, insects and other parasites or predators

19. Classification of Organic Herbicides by Chemistry Phenoxy herbicides Triazines Imidazolinone Sulfonylureas

20. Classification of Organic Herbicides by Chemistry Phenoxy herbicides – 2,4-D, 2,4-DP, 2,4,5-T – Behaves as an auxin causing hypertrophy (increase in cell size) – Sample structure

21. Classification of Organic Herbicides by Chemistry Triazines – Hexazinone – Have extreme soil mobility – Structure

22. Classification of Organic Herbicides by Chemistry Imidazolinone – Imazapyr – Structure

23. Classification of Organic Herbicides by Chemistry Sulfonylureas – Metsulfuron & sulfometuron methyl – Sample structure

24. Classification of Organic Insecticides by Chemistry Chlorinated hydrocarbons Organophosphates Carbamates Skip definitions

25. Classification of Organic Insecticides by Chemistry Chlorinated hydrocarbons – Dieldrin, aldrin, DDT, mirex, chlordane – Sample structure Return

26. Classification of Organic Insecticides by Chemistry Organophosphates – Malathion, azinphos-methyl, naled – Sample structure Return

27. Classification of Organic Insecticides by Chemistry Carbamates – Carbaryl (Sevin) – Structure

28. 2 Basic Chemical Groups for Herbicides Amines Esters

29. Amine (General Characteristics) Organic salt Water soluble Low volatility Low in its toxicity to fish Used for injection & cut- surface treatments Return

30. Esters (General Characteristics) Oil based Oil soluble / can be emulsified in water Generally highly volatile Highly toxic to fish Used for bark & foliar applications

31. Characteristics Amine vs. Ester Organic salt –Water soluble –Low volatility –Low toxicity to fish –Injections & cut surface treatments Oil based –Oil soluble or can be emulsified in water –High volatility –High toxicity to fish –Bark or foliar applications

32. LD 50 s of field formulations Garlon 4 --LD 50 1,419 mg/kg

33. LD 50 s of various products Comparison of oral LD50 (values for common herbicides and consumer goods) HerbicideLD 50 Consumer goodsLD 50 Paraquat (Gramoxone)~100Nicotine9 Triclopyr630Caffeine192 2,4-D666Bleach192 Pendimethalin (Prowl)1,050Tylenol338 Atrazine3,090Household Ammonia350 Glyphosate4,900Codeine427 Imazaquin (Image)>5,000Table Salt3000 LD 50 is the lethal dose that will kill 50% of the test animals in milligrams of product to kilograms of test animals body weight

34. LD 50 s of field formulations Garlon 4 --LD 50 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

35. Environmental behavior: Mode of action Selectivity Soil activity and mobility Persistence and breakdown Toxicity to humans and wildlife Application timing Weaknesses or limitations

36. Mode of Action: Herbicides Movement in the plant –Contact –Translocated Action in the plant –Inhibit protein synthesis, photosynthesis, or growth

37. 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

38. 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 Return

39. Contact Poisons Systemic Poisons Attractants –Phermones –Baits Repellents

40. Mode of Action: Contact Insecticide Pesticide which causes injury or death of insect through the touch rather than through inhalation or ingestion Return

41. 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

42. 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)

43. 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

44. Mode of Action: Life Stage Affected Ovicide – kills the eggs Larvicide – kills the immatures Adulticide – kills the adults

45. Mode of Action: Life Stage Affected Ovicide - Kills eggs

46. Mode of Action: Life Stage Affected Larvicide - Kills larval stage (immature) insects

47. Mode of Action: Life Stage Affected Adulticide –Kills adult insects

48. Mode of Action: Selectivity Many products express a degree of selectivity –Extremely variable from product to product –Biologicals often more selective than chemicals Many newer products are more selective Application method also influences selectivity (soil applied vs. foliar applied)

49. Soil Activity Soil Active Herbicide: applied to the soil. These chemicals are readily absorbed by plant roots or underground plant shoots, and subsequently negatively affects the plant in some manner

50. Soil Activity Non-Soil Active Herbicide: applied to the soil. These chemicals are bound to soil particles or organic matter and are essentially unavailable to affect plants

51. 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

52. Persistence & 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)

53. Persistence/Degradation: Process Drivers Temperature Relative humidity / Rainfall pH Insolation Soil or water biota –Macrophytes (visible plant life) –Microbial populations –Macrobes (worms, nematodes, etc)

54. Persistence & 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

55. Toxicity to Humans and Wildlife Varies by chemical Based on the target biochemistry of the product Much more later in this session

56. Off-site movement processes

57. Pesticide Movement & Degrade Runoff Leaching Degradation –Microbial –Physical –Hydrolysis –Photolysis –Pyrolysis Volatilization

58. 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 flooding rain

59. Pesticide Movement & Degrade Leaching –Also called percolation – the process whereby pesticide is moved down through the soil profile

60. Pesticide Movement & Degrade Microbial Degradation –Breakdown of pesticides by fungi, bacteria and other microscopic organisms

61. Pesticide Movement & Degrade Physical Degradation –Hydrolysis -- Breakdown of a pesticide by water

62. Pesticide Movement & Degrade Physical Degradation –Photolysis – breakdown of a pesticide by sun or other light

63. Pesticide Movement & Degrade Physical Degradation –Pyrolysis – the breakdown of a pesticide by heat or fire

64. Pesticide Movement & Degrade Volatilization – evaporation of a heated pesticide

65. Breakdown generalizations Hotter temperature = faster breakdown Higher relative humidity = faster breakdown More microbes = faster breakdown pH effect = chemical dependent More slope = more runoff More organic matter = more tie-up

66. 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

67. Questions?