1. Brian Jones Extension Agronomist
Understanding Herbicide Safety and Efficacy for Invasive Plant Management
Brian Jones
Extension Agronomist

2. Introduction
Chemical methods are well adopted for invasive plant management
Relative to other management methods, herbicides are:
Inexpensive
Easy to use
Fast acting
Must be used judiciously and safely…

3. Outline Herbicide Basics Impacts of Chemical Methods
Product Labels
Product Formulations
Herbicide Classification
Impacts of Chemical Methods
How herbicides work (review)
Effects of herbicides on human health and environment
Basic Herbicide Tactics

4. Herbicide Basics: Labels
The label is the law
Legally binding agreement between the EPA, the company and the end user
Label provides:
Directions for proper use
Safety information (PPE, REI)
Product name, common name, chemical name

6. Herbicide Basics: Labels
Signal Words
Warning
Caution
Danger or Danger/Poison
Hazard Level
Low
Moderate
High 

7. Herbicide Basics: Formulations
Formulations include active and inert ingredients

8. Herbicide Basics: Formulations
Adjuvants can have greatest impact on herbicide activity
Surfactants (surface acting agents)
Improve contact, droplet retention, and spread
Antidrift agents
Minimize non-target impacts
Color, odor or emetics
Improve human safety from ingestion

9. Herbicide Basics: Formulations
Many types of formulations
Water-soluble powder
Liquid
Wettable powder
Emulsifiable concentrates
Dry granule
Pellet
Provided on the label

10. Herbicide Basics: Classification
A working knowledge of classification is essential for:
Proper selection
Diagnosing injury symptoms
Managing herbicide resistance
Predicting herbicide interactions in the environment

13. How Herbicides Work
Kill or suppress plants by interfering with essential plant processes (e.g. photosynthesis)
Interactions between a herbicide and a plant from application to the final effect are known as the Mode of Action

14. Diagram of leaf cross-section showing mode of action of a foliar-active, systemic herbicide (e.g., atrazine) that inhibits photosynthesis. In this example, the herbicide is applied to and absorbed through the leaf, is translocated to the chloroplasts (site of action), and subsequently inhibits photosynthesis (mechanism of action)

16. Mechanism of Action
Avoid the repeated use of the same mechanism of action…why?
Reduce the risk of developing herbicide-resistant populations

17. Effects of Herbicides
Goal of pesticide regulation is no unreasonable adverse effects
Achieve this through risk management
RISK = EXPOSURE x TOXICITY
(how likely) (how bad)

18. Exposure (how likely)
Minimize exposure by following label and understanding the fate of herbicide after application
Four modes of entry into body:
Dermal (through the skin)
Oral (swallowing)
Inhalation (breathing in)
Ocular (through the eyes)

19. Exposure (how likely)
Most at risk for exposure when mixing and loading
Easiest way to avoid exposure???
WEAR PERSONAL PROTECTIVE EQUIPMENT…
LABEL WILL TELL YOU…

20. Exposure (how likely)
Processes that affect environmental fate of herbicides (transfer and degredation):

21. “The dose makes the poison.”
Toxicity (how bad)
“The dose makes the poison.”
Paracelsus
“What is it that is not a poison? All things are poison and nothing is without poison. It is the dose only that makes a thing not a poison.”

22. Toxicity (how bad) Acute and chronic toxicity CONCENTRATION TIME
Symptoms
Threshold

23. Toxicity (how bad) Measured by the median LD50
The dose that is lethal to 50% of the treated population (mg of compound / kg of body weight)

25. Herbicide Application Tactics
Tactics will vary according to:
Target species
Site conditions
Herbicide properties

27. Understanding Application Rate
Illegal to apply more than label states
Rates are given in terms of amount of formulated product per acre
Applicator must determine the pounds of active ingredient per acre to be applied

28. Understanding Application Rate
EX: Glyphosate formulation has 3 lbs active ingredient (ai) per gallon of product
Label application rate is 2 quarts product per acre
3 lb ai
gallon X
0.5 gallon
acre =
1.5 lb ai

29. Summary Herbicides are important tools for invasive plant management
Understand the fundamentals of:
Classification
Mode of action and formulations
Must be used according to the label
Avoid RISK
Take the time…wear the proper PPE
Understand the application tactics

30. THANK YOU!