5.2 Pesticide Formulations

Formulation is a handling decision, not a purchasing afterthought

40 CFR 171.103(c)(5)(ii) requires knowledge of types of formulations. National Core teaching treats formulation as the package that carries the active ingredient (AI) to the pest. The same AI sold as an emulsifiable concentrate, a granule, and a bait is three different measuring jobs, three different exposure routes at mix time, and three different off-target stories.

Keep the Oklahoma pictures attached to the abbreviations. A cotton insecticide is often an EC or SC poured into a boom tank. A pasture herbicide may be an amine liquid or a pellet for individual brush plants. A turf preemergence product may be a granule on a fertilizer spreader or a WDG in a lawn-spray tank. A 7A structural account leans on gel baits, station baits, void dusts, and aerosols. 7C stored-grain work uses fumigants that are already a gas or that generate gas. Extra fumigant certification, fumigation management plans, and commodity sealing are Chapter 10. This section only asks you to recognize fumigants as a gas formulation class with an inhalation special case—not as something you WALES-mix with a wettable powder.

Active ingredient versus formulated product

The active ingredient is the chemical that does the pesticidal job (the common name you learned in Chapter 4). The formulated product is what you buy: AI plus carriers, solvents, emulsifiers, dispersing agents, safeners, dyes, and other inerts. The label lists percent AI by weight. Many liquid labels also list pounds of AI per gallon.

If a wettable powder is 80% AI, then 5 pounds of product contain 4 pounds of AI (5 × 0.80). If an EC is 4 pounds AI per gallon, one quart of product contains 1 pound of AI. Rate tables may specify fluid ounces of product, pints of product, pounds of product, pounds of AI, fluid ounces per 1,000 square feet, or a percent solution. Read the column header before you pour. Writing “1.5” on a tank card with no unit is how a cotton load gets doubled and a turf lawn gets burned.

Brand name, common name, and chemical name were Chapter 4. Formulation codes usually sit next to the brand: 4E, 80WP, 75DF, 2L, 15G. Those suffixes tell you how to open, measure, mix, and apply. They are not marketing decoration.

Formulation abbreviations on the label

ME or CS (microencapsulated / capsule suspension) appears on some insecticides: tiny capsules suspended in liquid, often less odor and a different residual, still a suspension that needs agitation. If a tank-mix order gives microencapsulated products their own step, do not treat them as a generic “liquid.”

Emulsifiable concentrates (EC)

ECs dissolve the AI in an organic solvent and add an emulsifier so the product forms an emulsion in water. Advantages: easy to measure as a liquid, little powder dust at mixing, often good coverage on foliage, and usually less violent agitation than a wettable powder once the emulsion has formed.

Limitations National Core repeats because they show up in injury claims:

• Phytotoxicity from solvents, especially on sensitive ornamentals, grapes, vegetables, or heat-stressed turf
• Odor that generates school, hospital, and residential complaints even when the AI rate was legal
• Dermal absorption: solvents can carry AI through skin faster than many dry formulations of the same AI
• Damage to rubber hoses, gaskets, pump parts, and some tank liners
• Fire or vapor issues with some solvent systems in enclosed mixing areas

Cotton foliar insecticides and some pasture and right-of-way products still appear as ECs. If a turf customer wants no smell and no leaf burn, an EC may be the wrong formulation even when the common name is acceptable. Switching to an SC or WDG of a related AI is a formulation decision, still bound by each product’s label.

Wettable powders (WP)

WPs are finely ground AI plus wetting and dispersing agents. You suspend them in water; they do not dissolve. Advantages: often less phytotoxic than an EC of the same AI because there is no heavy solvent load, relatively economical, useful residual on some bark and foliage surfaces, and stable in storage if kept dry.

Limitations:

• Inhalation hazard when opening and measuring the dusty concentrate—this is a mixer/loader problem even if the dilute spray is milder
• Abrasion of pumps, nozzles, and tank walls; WPs sandblast equipment
• Constant agitation or the powder settles into a cement-like layer in the sump
• Clogged screens and tips
• Visible residue on dark turf, cars, and house siding

A peanut or pecan WP fungicide that looks cheap per acre can still be the wrong package in a small residential tank with a weak pump. If you add a WP on top of an EC without enough water and time, you also manufacture a physical incompatibility problem that Section 5.3 will blame on mixing order.

Water-dispersible granules and dry flowables (WDG / DF)

WDG/DF products are the usual modern substitute for many WPs: the same suspension idea, but granules that raise less dust and pour more cleanly. You still need water, time, and agitation to disperse them before you add other products. Incomplete dispersion looks like “the mix went bad” twenty minutes later. They clog if dumped into a nearly empty tank or added on top of an EC oil film. Measure by weight when the label gives pounds; a loosely filled coffee can is not a scale.

Flowables and suspension concentrates (F / SC / L)

The AI is already ground and suspended in a liquid carrier. Shake the jug (solids settle in storage), measure a liquid, and keep the spray tank agitated. Advantages: easier measuring than WP, far less mix-time dust than WP. Limitations: freeze/thaw can ruin some SCs, residue can still show, and they remain mildly abrasive compared with true solutions. Cotton insecticides and turf fungicides are commonly SCs in Oklahoma spray trucks.

Soluble powders and true solutions (SP / SL)

These dissolve. Once in solution, particles should not settle, so agitation is to mix, not to keep grit hanging. Dry SP concentrates can still be an inhalation risk when you open the bag. Cold water and a dirty tank can keep a “soluble” product from going into solution as fast as the label assumes. If crystals sit in the strainer, you have a measuring and water-temperature problem, not a new pest.

Granules (G) and pellets (P)

Granules are ready to apply with a spreader. Advantages: little spray drift compared with a boom, often lower dermal exposure than mixing an EC, no spray tank, useful for soil insects, turf preemergence, fire-ant products, and some pasture applications.

Limitations:

• Spreader calibration and pattern (overlap, missing strips, walking speed) are easy to get wrong
• Poor choice when you need foliar coverage
• Some granules need soil moisture or irrigation to release the AI
• Birds, pets, and children may pick up granules or pellets if placement rules are ignored
• Measuring by volume is not the same as pounds per acre when bulk density differs between products or between a full bag and a fluffy leftover

Pellets are larger and often more uniform. Range and pasture brush products may be pellets placed at the base of mesquite or locust. That is still a pesticide application with a labeled rate per acre or per plant, not a casual toss.

Dusts (D)

Dusts are finely divided, ready to use, and good at coating irregular surfaces. Livestock dusts are mostly historical in many operations; structural void treatments still use dusts in 7A work. The Core problem is particle drift and inhalation. A dust cloud does not respect a property line, an HVAC return, or a respirator left in the truck. Agricultural dusts are uncommon on modern Oklahoma boom sprayers. Never substitute a dust for a bait program because both are “dry.” A void dust and a cockroach gel solve different placement problems.

Baits

Baits combine a small amount of AI with an attractant. 7A gel baits for German cockroaches and tamper-resistant rodent stations at elevators and food plants are the structural picture. Fire-ant baits and some slug products appear in turf and landscape work. Advantages: targeted placement, low broadcast volume, often less surface residue than a perimeter flood-spray.

Limitations: competing food (sanitation), secondary poisoning and pet access, bait shyness, and repellent sprays applied over a bait placement so insects stop feeding. A cotton foliar EC and a kitchen gel are both insecticides. They are not the same formulation skill. Many bait labels also tell you not to tank-mix or not to spray the bait spot with a contact insecticide.

Aerosols, ready-to-use products, and ULV

Aerosols are pressurized, ready-to-use, fine droplets. Indoor flush-and-kill, crack treatments, and some greenhouse uses are typical. Flammability, inhalation in small rooms, and over-application are the hazards. An aerosol is not a substitute for a 7C fumigant; it does not penetrate a grain mass.

Ready-to-use (RTU) liquids are already diluted. Advantages: no mixing math, lower concentrate exposure than opening a jug of EC. Limitations: high cost per pound of AI, heavy containers, no custom rate, and they can still drift, stain, or burn plants. Hose-end RTU turf products still have labeled sites and rates.

Ultra-low volume (ULV) applies a very small volume of highly concentrated product as fine droplets. Public-health mosquito adulticiding is the usual picture; some crop ULV labels exist. Fine droplets drift. ULV needs labeled equipment and droplet-size statements. It is not a pickup-truck hose-end sprayer set to “fine.”

Fumigants as a formulation class

Fumigants are gases, or solids/liquids that become gas (aluminum phosphide tablets or pellets in stored wheat; sulfuryl fluoride in structures; some soil fumigants). They penetrate commodities and spaces that sprays cannot. They are acute inhalation products with buffer, posting, and monitoring rules on the label. Oklahoma 7C and related fumigation work requires extra certification beyond Core (Chapter 10). For this chapter: if the formulation is a fumigant, you do not tank-mix it like an EC, you do not treat it as a residual crack spray, and you do not borrow a phosphine product for a 7A cockroach job because “both kill bugs.”

Dry versus liquid handling hazards

40 CFR 171.103(c)(5)(iii) and (iv) include formulation toxicity and hazards associated with use. Mixer/loader exposure is often higher than the exposure from the dilute spray.

PPE minimums are on the label for mixers/loaders and may be stricter than for diluted application. Chapter 7 covers PPE selection. Here, remember that changing WP to SC can change mixer exposure even when the common name is unchanged, and that EC solvent can change dermal absorption even when the AI rate in the crop is the same.

Choose formulation with the site in mind. Cotton can tolerate some EC insecticides that would burn an ornamental bed. Pasture pellets should not be spread like turf fertilizer on a school playground. Turf WDG that leaves a white film on a dark cultivar creates a complaint even when the rate was legal. 7A baits fail when a technician “mixes in” a repellent aerosol on the same spots. 7C gas has no business in a backpack sprayer.