5.2 Pesticide Types, Formulations & Adjuvants
Key Takeaways
- Pesticide types are classified by target pest — insecticides, miticides, herbicides, fungicides, nematicides, rodenticides, fumigants, and more — while Mode of Action names the biochemical target site used for resistance rotation.
- A formulation is the active ingredient plus inert carriers and solvents; the label's formulation code (EC, WP, WDG, G, D, F/SC, ME, SP, ULV, B) dictates PPE, drift, inhalation, and dermal hazards.
- Emulsifiable concentrates present the highest dermal-absorption risk; dusts present the highest drift and inhalation risk; microencapsulated products are an extreme bee hazard.
- Adjuvants — surfactants, crop oils, stickers, drift-reduction polymers, water conditioners such as AMS — improve performance but may be used only as the label directs.
- Synergism increases combined effect beyond the sum of the products, antagonism reduces it, and tank mixes are lawful only when every component label permits them.
Pesticide Types, Formulations & Adjuvants
Federal core standards require certified applicators to demonstrate practical knowledge of the types of pesticides, the types of formulations, and the compatibility, persistence, and toxicity characteristics that flow from those choices (40 CFR 171.103(c)(5)). Formulation is not fine print: it determines PPE requirements, drift and inhalation hazards, dermal absorption rates, mixing order, bee risk, and even whether a pest is controlled at all.
Types of Pesticides by Target Pest
Pesticides are classified first by the organism they control. Under FIFRA and NRS 586.195, a pesticide is any substance intended to prevent, destroy, repel, attract, or mitigate a pest — and the term also sweeps in plant regulators, defoliants, and desiccants.
| Pesticide Type | Target Pest | Representative Examples |
|---|---|---|
| Insecticide | Insects | Bifenthrin, imidacloprid, carbaryl |
| Miticide / Acaricide | Mites, ticks | Abamectin, bifenazate |
| Herbicide | Weeds, unwanted plants | Glyphosate, 2,4-D, dicamba |
| Fungicide | Fungi (mildews, rusts, rots) | Chlorothalonil, azoxystrobin |
| Bactericide | Bacteria | Copper compounds |
| Nematicide | Nematodes | Metam sodium (also a soil fumigant) |
| Rodenticide | Rodents and other vertebrates | Brodifacoum, diphacinone baits |
| Avicide | Pest birds | Avitrol (restricted-use) |
| Molluscicide | Snails, slugs | Metaldehyde |
| Piscicide | Pest fish | Rotenone |
| Predacide | Predatory animals | Sodium cyanide (M-44), sodium fluoroacetate — in Nevada limited to USDA Wildlife Services personnel |
| Plant Growth Regulator | Plant growth processes | Ethephon, gibberellic acid |
| Defoliant / Desiccant | Foliage removal / tissue drying | Diquat |
| Repellent / Attractant | Pest behavior | DEET, pheromone lures |
| Antimicrobial | Microbes on surfaces (disinfectants, sanitizers) | Quaternary ammonium, sodium hypochlorite |
| Fumigant | Pests via lethal gases | Sulfuryl fluoride, phosphine, metam sodium |
| Wood Preservative | Wood-destroying fungi and insects | Copper naphthenate, creosote (RUP) |
Type vs. Mode of Action: The pesticide type names the target organism. The Mode of Action (MoA) names the biochemical target site inside the pest — the IRAC, FRAC, and HRAC group codes used for resistance rotation (Section 5.4).
Formulations: Why the Code Matters
A formulation is the physical mixture of active ingredient plus inert carriers, solvents, and additives, blended for storage, mixing, and delivery. Labels print the formulation code next to the brand name (for example, 2EC, 80WP, 75WDG), and every downstream safety rule depends on it.
| Code | Formulation | Physical Form | Key Characteristics & Hazards |
|---|---|---|---|
| EC | Emulsifiable Concentrate | a.i. dissolved in petroleum solvent + emulsifier | High dermal-absorption and phytotoxicity risk; no dust; easy measuring |
| WP | Wettable Powder | Dry powder + wetting agent | Inhalation hazard during mixing; suspends (never dissolves) — needs constant agitation; abrasive to pumps |
| WDG / DF | Water-Dispersible Granule / Dry Flowable | Dry granules that disperse | Low-dust WP alternative; still requires agitation |
| G | Granule | a.i. coated on clay pellets | Soil-applied; negligible drift; low dermal hazard |
| D | Dust | Fine dry particles, ready-to-use | Highest drift and inhalation hazard; clings to bees |
| F / SC | Flowable / Suspension Concentrate | Finely ground a.i. suspended in liquid | WP-like behavior in liquid form; easy measuring; agitation required |
| ME / CS | Microencapsulated | a.i. sealed in polymer capsules | Timed release; capsules mimic pollen — extreme bee hazard (Section 3.3) |
| SP | Soluble Powder | Dissolves completely | No residue or agitation once dissolved |
| SL | Soluble Liquid | True solution | No settling; simple handling |
| ULV | Ultra-Low Volume | Concentrated technical product | Applied nearly undiluted in tiny droplets; specialized equipment |
| B | Bait | a.i. + food attractant | Rodent and structural pest control; many uses require tamper-resistant stations |
| RTU | Ready-to-Use | Pre-diluted | Consumer and structural use; no mixing |
| A | Aerosol | Pressurized can | Space treatment in structures |
| Fumigant | Gas or gas-generating solid | Stored-product and soil treatment | Highest acute inhalation hazard; separate certification category in Nevada |
Choosing Among Formulations
Selection turns on: the target site and pest, available equipment, drift and inhalation hazards, dermal toxicity to the handler, persistence required, environmental fate (Section 3.2), compatibility with tank partners, and cost per treated acre. A formulation that is safer to apply may carry longer residues — weigh both.
Adjuvants: Tank-Mix Performance Additives
An adjuvant is a substance added to the spray mixture to improve performance or handling. Adjuvants are used only as the label directs — adding them against label directions can cause phytotoxicity, illegal residues, or physical incompatibility.
| Adjuvant Class | Function in the Tank |
|---|---|
| Non-Ionic Surfactant (NIS) | Lowers surface tension so droplets spread and wet foliage evenly |
| Crop Oil / Methylated Seed Oil (COC/MSO) | Penetrates waxy leaf cuticles; speeds uptake |
| Sticker | Improves rainfastness and residue retention |
| Drift-Reduction Polymer / Deposition Aid | Enlarges droplet spectrum, cutting driftable fines |
| Compatibility Agent | Keeps multi-product mixes uniformly dispersed |
| Water Conditioner (e.g., AMS) | Ties up hard-water calcium and magnesium cations that would otherwise antagonize products such as glyphosate |
| Buffer / Acidifier | Controls tank pH for alkaline-sensitive products |
| Defoamer | Suppresses foam that interferes with filling and agitation |
| Dye / Marker | Makes the treated swath visible to prevent skips and overlaps |
Compatibility, Synergism & Antagonism
- Compatibility: Two products can be mixed without physical or chemical breakdown. Verify unknown combinations with a jar test (Section 4.4).
- Synergism: The combined effect is greater than the sum of the individual effects — beneficial for control but capable of multiplying crop injury.
- Antagonism: The combined effect is less than expected — for example, hard-water cations binding glyphosate and cutting weed control.
- Legal Check: A tank mix is lawful only when every component label permits the combination and labeled maximum rates are respected (FIFRA Section 2(ee), Section 5.1).
Persistence & Residual Activity
- Residual (persistent) products keep killing for weeks to months — valuable for soil-applied weed control, but they raise crop-rotation carryover and groundwater-leaching concerns (Section 3.2).
- Non-residual (contact) products degrade within days — safer for rotations and harvest intervals, but they demand precise timing against the pest's vulnerable life stage (Section 5.4).
- Persistence interacts with soil texture, organic matter, pH, and Nevada's intense summer heat and UV radiation, all of which accelerate or retard breakdown.
Which formulation type carries the highest dermal-absorption concern during mixing and loading because its active ingredient is dissolved in a petroleum-based solvent?
An applicator adds ammonium sulfate (AMS) to hard spray water before mixing glyphosate. What is the adjuvant's function?
Two products are tank-mixed and the combined pest control is greater than the sum of each product applied alone. This interaction is called: