7.1 Solutions, Suspensions, Emulsions, and Liquid Formulations

Why formulations are a General Standards topic

Georgia Rule 40-21-3-.01 lists pesticides among the eight General Standards every commercial applicator must know: types, formulations, compatibility, hazards, resistance, and dilution. That list is the National Pesticide Applicator Certification Core Manual, 2nd edition, Chapter 4, written into Georgia competency language. UGA Pesticide Safety Education Program general-standards manuals follow that same core. You will take a computerized General Standards exam plus at least one category exam, 2.5 hours for the sitting, at a Georgia Technical College through gapestexam.com. You must score 70% on both portions. Formulation questions live on the core portion. A Category 21 applicator spraying peanuts in Tift County and a Category 41 applicator running a mosquito ultra-low-volume route in Chatham County answer the same solution-versus-suspension items before they ever see a category question.

Do not confuse this credential with the Georgia Structural Pest Control Commission Certified Operator exams (HPC/WDO/FUM). Those are a different license family. Georgia Department of Agriculture Category 35 (industrial, institutional, structural, and health-related pest control) also does not replace an SPCC operator card.

A pesticide formulation is what you buy: the active ingredient plus other ingredients (study manuals still say inert ingredients). The active ingredient is the chemical intended to control the pest. Other ingredients—carriers, solvents, emulsifiers, wetting agents, dyes, stabilizers—make the product measurable, mixable, sprayable, or shelf-stable. They are not a safety guarantee. Petroleum solvents in many liquid concentrates increase dermal absorption and can injure plants even when the active ingredient is relatively gentle on the crop. Modern labels often print other ingredients instead of inert because solvents, emulsifiers, and carriers can be toxic, flammable, or phytotoxic on their own.

The front panel states percent active ingredient by weight for dry products, or pounds of active ingredient per gallon for many liquids, and the brand name usually carries a formulation code. 4EC means about four pounds of active ingredient per gallon as an emulsifiable concentrate. 80WP means 80 percent wettable powder. 5G means 5 percent granules. That code is how you later convert a labeled rate into a tank load. It is not the application rate itself.

Solutions, suspensions, and emulsions

Before you memorize letter codes, lock the three physical systems. Every liquid in a spray tank is one of these, or an invert variation of an emulsion.

A solution has the active ingredient dissolved in a liquid at the molecular level. It is usually clear or uniformly tinted. It does not settle, you cannot filter the active ingredient out with an ordinary strainer, and it does not need agitation to stay mixed once it has dissolved. Water-soluble concentrates and many ready-to-use liquids behave this way.

A suspension has solid particles dispersed in a liquid. It is cloudy. Without agitation the particles fall to the bottom. Wettable powders, water-dispersible granules, and flowable or liquid concentrates become suspensions when you dilute them. If the agitator dies on a peanut boom in Terrell County, a suspension settles in the tank sump and in the boom lines.

An emulsion is one liquid dispersed as droplets in another liquid it does not dissolve in. The usual agricultural emulsion is oil-in-water: solvent droplets that hold the active ingredient, coated with emulsifier, hanging in the water carrier. Emulsions look milky. They may cream if they sit, so many labels still want some agitation even though you are not suspending a solid.

An invert emulsion reverses that picture: water-in-oil. The spray is thick, closer to mayonnaise than to milk. Droplets are large and heavy, so they resist evaporation and drift. Georgia Category 27 Right-of-Way crews see invert systems on highway and utility vegetation jobs where a light water spray would move onto cotton, pecans, peaches, or a home garden.

Emulsifiable concentrates (EC or E)

Most emulsifiable concentrates contain a liquid active ingredient, one or more petroleum-based solvents, and an emulsifier. National Core still teaches a working range of about 25 to 75 percent active ingredient, often 2 to 8 pounds of active ingredient per gallon. Pour an EC into water and it turns milky. That color is the emulsion forming, not dirty well water.

ECs are everyday tools in Georgia Category 21 Agricultural Plant programs. Many peanut and cotton herbicides, insecticides, and plant-growth regulators ship as ECs because they meter through a nurse-tank valve, they do not plug 50-mesh screens the way wettable powders do, and they leave little visible powder on a leaf. They fit trailer sprayers, high-clearance sprayers, and, when the label and Category 34 Aerial rules allow, aircraft over those same crops.

Recite the advantages: easy to handle, measure, and mix; little agitation compared with wettable powders; not abrasive to pumps and nozzles; little visible residue on treated surfaces.

Recite the disadvantages the exam will test: high concentration makes a measuring error an overdose; solvents move through skin faster than water-based mixes, so mix/load dermal exposure is serious; solvents can be phytotoxic to cotton, peanuts, ornamentals, and succulent tissue; solvents attack rubber hoses, gaskets, and some plastics; some ECs pit or stain paint; many are combustible. Treating an EC jug like water fails both this domain and the safety domain.

Solutions (S), ready-to-use (RTU), and ultra-low volume (ULV)

A solution (S) is already dissolved in water or in oil. Water-based solutions are relatively easy on plants and need no agitation after they dissolve. Oil solutions used on livestock (Category 22), dormant trees, or sites where water would run off can burn foliage and may be flammable.

Ready-to-use (RTU) liquids often contain about 1 percent or less active ingredient already diluted. You do not mix them. Category 35 industrial accounts and some ornamental products use RTU to cut mixing errors. You pay in cost per pound of active ingredient, extra containers to rinse or dispose, and bulk that is inconvenient on a large peanut or cotton acreage.

Ultra-low-volume (ULV) concentrates may approach 100 percent active ingredient. You apply a very small volume, sometimes undiluted, through specialized nozzles or rotary atomizers that produce a narrow droplet spectrum. Georgia Category 41 Commercial Mosquito Control and Category 31 Public Health programs use ULV adulticides on truck-mounted or aerial equipment. Advantages: little product to haul, little agitation, large area from a small tank. Disadvantages: high drift, specialized calibration, easy overdosing, high dermal absorption, and phytotoxicity from concentrated solvents. ULV is not a boom spray with the gallons turned down. It is a different formulation class with different equipment and different off-target risk.

Invert emulsions, flowables, aerosols, and liquid baits

Invert emulsions put a water-soluble pesticide into an oil carrier—often fuel oil—with a special emulsifier. Large droplets and slow evaporation cut drift and washoff on rights-of-way. Underside-of-leaf coverage is poor because the droplets are heavy. Do not substitute an invert mix for drift-reduction practice on a water-based cotton spray unless that product is labeled for the site.

Flowables (F) and liquids (L), including many suspension concentrates (SC), start with a solid active ingredient that will not dissolve in water or oil. The manufacturer grinds it, suspends it in a little liquid with dispersing agents, and sells a thick pourable jug. In your tank it is still a suspension and still needs agitation. Versus a wettable-powder bag, a flowable is easier to measure and raises less mixing dust. Versus an EC, it can still abrade equipment, leave visible residue, settle in dead-end hoses, and leave sludge that is hard to triple-rinse.

Aerosols (A) include pressurized ready-to-use aerosols and formulations for smoke or fog generators. A can is convenient in a Category 35 account and uneconomical in a pecan orchard. Fogging an enclosed space means clearing people and animals, following the label on air handlers, and ventilating before reentry. Inhalation and flammability in a closed warehouse or food plant are the hazards, not it is only a mist.

Liquid baits combine active ingredient with a liquid food attractant. Ant stations, some rodent liquids, and certain fly baits belong here. Tamper-resistant placement protects children, pets, and wildlife. An open plate of liquid bait in a school kitchen is a misuse even if the ants die.

Georgia scenario: the milky peanut tank

A Category 21 crew in Tift County builds a postemergence peanut tank with a 4EC herbicide. The water turns milky when the first pint hits—that is the emulsion, and it is expected. A helper wants to skip agitation because ECs are not powders. Light agitation is still the professional default, and it is required if a flowable or wettable-powder partner is in the same tank. The helper also wants to dump EC into an empty tank and add water later. Carrier first, agitation on, then products. Concentrated EC plus a second concentrate is how tanks gel.