Pesticide Formulations

Introduction

Chapter Four focuses on pesticide formulations.
Pesticides can be confusing due to the variety of formulations.
The optimal formulation depends on the specific job; there's rarely a universal solution.
Consult experts if you have formulation questions.

Learning Objectives

Describe a pesticide formulation.
Explain why pesticides are formulated for end-use applications.
Differentiate between active and inert ingredients on a pesticide label.
Understand abbreviations for common formulation types (e.g., WP for wettable powder).
List factors to consider when selecting a formulation for a specific situation.
Discuss the properties of common formulations.
Evaluate the advantages and disadvantages of different formulations.
Explain the role of adjuvants.

What is a Pesticide Formulation?

A combination of active and inert ingredients creating an end-use pesticide product.
Pesticides are formulated to improve safety and ease of use.
Pure, technical-grade active ingredients are often unsuitable for direct application because:
- Some are extremely toxic in concentrated form.
- Many don't mix well with water.
- Many are unstable.
- Some are difficult or unsafe to handle, transport, or store.
Inert ingredients are added to address these issues.

Inert Ingredients

Inert ingredients have no pesticidal activity.
Some act as diluents or carriers.
Inert ingredients make the formulated product safer, easier to handle, more effective, or some combination of all three.

Components of a Pesticide Product

Active ingredient: Controls the target pest.
Carrier/Diluent: Organic solvent or mineral clay (in powders).
Surface Active Ingredients: Stickers and spreaders.
Additives: Stabilizers, dyes, and chemicals to improve safety or pesticidal activity.

Formulation Types

Selecting the right formulation is crucial for effective pest control.
If you have questions, consult your pesticide distributor or local extension agent.

Solutions

Made by dissolving a substance in a liquid.
A true solution is a homogenous mixture and cannot be separated by filtration or mechanical means.
Once made, a true solution will not settle out therefore it won't need shaking or stirring to keep the mixed components in solution.
Solutions are transparent and allow light to pass through.
Examples: Sweetened iced tea, salt water.

Suspensions

Liquid mixture formed by dispersing fine, small particles in a liquid.
Solid particles do not dissolve in the liquid carrier.
Must be agitated to maintain uniform particle distribution. (undissolved parts of the suspension mixture will settle or float to the top otherwise.)
Most suspensions are cloudy or opaque (they will not allow light to pass through).
Pesticide products formulated as suspensions are not water soluble.
Label instructions: Shake well before measuring and mixing.
Apply with spray equipment that has enough agitation to keep the final mixture evenly distributed in the spray tank during application.
Example: Flour and water.

Concentrates (ULV)

Concentrates, or Ultra Low Volume (ULV) formulations, can be 10x less expensive than ready-to-use formulations per unit area treated.
Often more toxic than dilute formulations.
Require more handling, increasing exposure risk to the user.

Emulsions

A special kind of suspension: a mixture of droplets of one liquid in another.
Each ingredient retains its unique properties and identity.
Made by dissolving an active ingredient in an oil-based solvent, then diluting with water.
Agitation may be necessary to prevent separation.
Emulsions typically have a milky appearance.
Emulsifiable concentrates (E or EC) are a type of emulsion.
Example: Homogenized milk.

Ready-to-Use (RTU) Formulations

Require no further dilution before application.
Contain a low concentration of active ingredient (often 1% or less per unit volume).
Some are petroleum-based, others are water-based.
Common for pest management professionals and non-occupational users.

Wettable Powders (WP)

Dry, finely ground solid materials.
Usually include wetting and/or dispersing agents.
Mixed with water and applied as a spray, or applied dry/as a liquid suspension.
Contain 5-95% active ingredient (usually 50% or more).
Particles don't dissolve in water; form a suspension.
Require constant agitation to prevent settling.
Effective for most pest problems and spray equipment (with agitation).
Excellent residual activity and generally don't harm treated surfaces.
When applied, most of the pesticide remains on the surface, even porous materials (only water penetrates).

Advantages:

Easy to store, transport, and handle.
Less likely to harm treated plants, animals, and surfaces (usually not phytotoxic).
Lower risk of skin and eye absorption compared to ECs.

Disadvantages:

Not easy to measure (often must be weighed) or mix.
Inhalation hazard during measuring and mixing of concentrated powders.
Require good, constant agitation.
Nozzles can show wear due to the powder's abrasive nature.
Difficult to mix in very hard or alkaline water.
May clog nozzles and screens if not mixed properly.
Can leave visible residues on treated surfaces.

Dusts (D)

Most are ready-to-use, containing a low percentage of active ingredient (usually 10% or less).
Some are concentrates requiring mixing with dry inert carriers.
Made of one or more active ingredients plus a fine, dry, inert carrier (talc, chalk, clay, nut hull, volcanic ash, etc.).
Small particle size requires careful handling to prevent non-target exposure and drift.
Not water-soluble; always used dry, do not mix with a liquid solvent.
Used as seed treatments and in some agricultural operations.
Useful in structures for crack and crevice treatment and spot treatments.
Effective for lice, fleas, and external parasites on pests and livestock.

Tracking Powders:

Special dusts for insect and rodent monitoring/control.
Finely ground dusts with an absorbed stomach poison.
Pests pick up the dust on their bodies and ingest it while grooming.
Effective where bait acceptance is poor.
Non-toxic powders (talc, flour) can also monitor rodent activity.

Baits (B)

Active ingredient mixed with food or another attractive substance.
Attracts the pest or is placed where the pest will find it.
Many baits are solid (blocks, granules, pellets), but some are liquids, pastes, or gels.
Low active ingredient concentration (usually <5%).
Used inside buildings for ants, cockroaches, flies, and other insects.
Used outdoors for vertebrate pests (rodents, mammals, birds), snails, slugs, and some insects.
Applicators must place bait stations in safe, strategic locations, following label directions to protect children and non-target organisms.

Advantages:

Ready to use.
The entire area does not need to be covered because the pest goes to the bait.
Controls pests that move in and out of an area

Disadvantages:

Attractive to children and pets.
Kill domestic animals and non-target wildlife.
Require careful placement and inspection.
Pests may prefer other food sources.
Dead vertebrate pests may cause odor problems.
Baits can serve as a food supply for target/other pests if not removed.
May not work when pests have many other food/water sources.

Ultra Low Volume (ULV)

Applied in very small quantities (e.g., $0.5$ gallons or less per acre).
Often undiluted formulations, approaching 100% chemical activity.

Advantages:

Easy to handle, small quantities.
Easier to transport and store.
Little agitation required.
Not abrasive to equipment; won't plug screens.

Disadvantages:

Difficult to keep on target (drift hazard).
Easily absorbed through the skin.
Cause rubber and plastics to deteriorate.
Require careful calibration due to high concentration.

Tank Mixing

Combining pesticides with other pesticides or fertilizers.
Premixes are available, or products can be combined at the time of application.
Tank mixing: Combining two or more crop production products (pesticides or fertilizers) and applying them simultaneously.
Saves time, labor, fuel, and equipment.
Reduces soil compaction and risk of mechanical damage.
Federal law allows tank mixing unless prohibited by the labeling of one or more components.
All dosages must be at or below the label rate for each component.
Refer to Chapter 10 in the Core Manual for information on incompatibility, compatibility testing, and tank mix preparation.

Adjuvants

Chemicals that affect how a pesticide works.
Improve pesticide action or change characteristics of a pesticide formulation/spray mixture.
Most end-use pesticide products (especially foliar applications) contain adjuvants.
Also added to tank mixes.
Increase effectiveness and/or safety.
Have no pesticidal activity alone.
Customize product for specific needs or compensate for local conditions (e.g., pH).
EPA does not register adjuvants, so there are no standards for composition, quality, or performance.
Contact the manufacturer for information.
Consult the pesticide product label before using any adjuvant.

Types of Adjuvants

Anti-foaming/Defoaming Agents: Reduce foaming of spray mixtures.
Buffers/pH Modifiers: Allow pesticides to be mixed with diluents or other pesticides from different acidity or alkalinity.
- Most pesticide solutions/suspensions are stable between pH $5.5-7$ (slightly acidic to neutral).
- Water outside this range may cause rapid degradation.
- Add buffer to spray tank water first and mix well before adding pesticides or other adjuvants.
Compatibility Agents: Help combine pesticides that don't mix well; reduce incompatibility issues.
Drift Control Additives/Deposition Aids: Reduce drift and increase average droplet size, or lower the number of fines (very fine droplets).
Emulsifiers: Allow petroleum-based pesticides (ECs) to mix with water.
Extenders: Keep pesticides active on a target for an extended period of time.
- Some adjuvants manufacturers use this name for stickers, so you want to not be confused by that.
Invert Emulsifiers: Allow water-based pesticides to mix with a petroleum carrier.
Plant Penetrants: Allow pesticides to pass through the outer surface or epidermis of treated foliage.
- Certain plant penetrants may increase penetration on some, but not all plant species.
Safeners: Reduce toxicity of a pesticide formulation to the pesticide handler or to the treated surface
Spreaders: Allow pesticides to form a uniform coating layer over the treated surface.
Stickers: Allow pesticides to stay on a treated surface.
- Some increase adhesion of solid particles to treated surfaces, reducing wash-off.
- Others reduce evaporation or slow photo-degradation.
Surfactants: Make water "wetter"; allow less compatible substances to mix.
Thickeners: Increase the viscosity or thickness of spray mixtures.
- Reduce drift or slow evaporation.
- Increase the amount of time which the active ingredient can be absorbed by or penetrate the plant foliage.
Wetting Agents: Allow wettable powders to mix with water.

Thoughts on Choosing Adjuvants

Ensure it's the right one for the specific site and situation. Look carefully at the label.
Consult pesticide distributors and local extension agents.
Ask yourself, is an adjuvant recommended, and if so, what type?
Be careful not to make substitutions.
Note that some product labels may recommend an adjuvant for one type of use/site but prohibit it for another.
Many end-use formulated products already have adjuvants, and adding more can decrease efficacy, be careful about that.
Use only adjuvants manufactured for agricultural or horticultural use. Do not use industrial products or household detergents.
No adjuvant is a substitute for good application practice.
Be skeptical of claims such as improved root uptake or keep spray equipment clean unless there's research-based evidence.
Only use products tested and found effective for your intended use.
Test spray mixes with adjuvants on a small area before full-scale use.

Key Considerations for Choosing a Pesticide Formulation

Ingredients: Active ingredient controls the pest; inert ingredients include carriers, diluents, and adjuvants.
Formulation Type: Check the front panel of the label for the formulation type. Safety data sheet describes the formulation.
Properties and Evaluation: Know the properties and evaluate the pros/cons of various formulation types.
Factors to Consider: Risks/benefits, practicality for the site, and whether it will provide effective control.

Conclusion

Understanding properties of common formulations helps avoid problems.
Familiarize yourself with formulation types and active ingredient properties to understand the characteristics of the products you use and how to apply them properly.
Take the quiz and review topics you need to study further.
Read the relevant section in the study manual.