5.1 Liquid Formulations (EC, S, F, ULV)

5.1 Liquid Formulations (EC, S, F, ULV)

Pesticide active ingredients (ai) are rarely applied in their pure, technical-grade chemical state. Technical-grade active ingredients may be insoluble in water, volatile, toxic, or difficult to handle safely. To transform these raw chemicals into effective, commercially viable products, manufacturers combine active ingredients with inert ingredients—such as liquid solvents, emulsifiers, wetting agents, thickeners, and mineral carriers—to produce a pesticide formulation.

Liquid formulations are among the most widely used pesticide products across agricultural production, commercial pest control, turf and ornamental management, and rights-of-way maintenance in Tennessee. Selecting the appropriate liquid formulation requires understanding how different products behave inside the spray tank, their agitation demands, their abrasive impact on application equipment, and their safety hazards to applicators and non-target organisms.

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Emulsifiable Concentrates (EC or E)

An Emulsifiable Concentrate (EC or E) is formulated by dissolving a liquid or solid active ingredient in one or more petroleum-based organic solvents, accompanied by chemical emulsifiers. Emulsifiers are surface-active agents that allow oil-based chemicals to mix uniformly with water.

Physical Behavior and Appearance

When an EC product is added to a spray tank containing water, the emulsifiers cause the petroleum-pesticide solution to disperse into microscopic oil droplets, forming a milky-white emulsion. Because an emulsion is a physical mixture of oil droplets suspended in water rather than a true solution, the oil phase will eventually separate and float to the top of the tank if the spray mixture sits idle for an extended period.

Advantages and Disadvantages of EC Formulations

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Solutions (S) and Ready-to-Use (RTU) Liquids

A Solution (S) is formulated by dissolving a water-soluble or oil-soluble active ingredient completely in a liquid carrier (such as water or mineral oil). Once dissolved, the active ingredient molecules are uniformly dispersed throughout the liquid solvent.

Physical Behavior and Equipment Impact

Because a solution is a true chemical solution, it will not separate or settle out over time. Solutions require no tank agitation once thoroughly mixed. Furthermore, solutions are completely non-abrasive to pumps, pressure regulators, and spray nozzles, and they do not clog filter screens or small nozzle orifices.

Solution Formulations

• Concentrated Solutions (S or C): High-concentration liquid products designed to be diluted with water or liquid fertilizer carriers in the spray tank before application.
• Ready-to-Use (RTU): Low-concentration liquid solutions (typically 1% or less active ingredient) sold pre-mixed in spray bottles or small containers. RTUs require no measuring or dilution, minimizing applicator exposure during loading.
• Ultra-Low Volume Solutions: Concentrated oil-soluble solutions formulated specifically for ultra-low volume application machinery.

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Flowables and Suspension Concentrates (F or SC)

Many pesticide active ingredients are insoluble solids that cannot be dissolved in water or petroleum solvents. To create a liquid formulation from an insoluble solid, manufacturers finely grind the active ingredient into a microscopic powder and suspend it in a thick liquid carrier (composed of clay, water, and thickening agents). This product is designated as a Flowable (F) or Suspension Concentrate (SC).

Physical Behavior and Mixing Characteristics

A flowable formulation has the physical consistency of thick liquid clay or a dense milkshake. When added to water in a spray tank, the solid active ingredient particles disperse into suspension.

LIQUID FORMULATION TANK BEHAVIOR COMPARISON

1. EMULSIFIABLE CONCENTRATE (EC)
   [ Oil droplets + Emulsifier + Water ] ===> Milky White Emulsion (Mild Agitation Needed)

2. SOLUTION (S)
   [ Dissolved ai + Water ]             ===> Clear True Solution (Zero Agitation Needed)

3. FLOWABLE / SUSPENSION (F / SC)
   [ Finely Ground Solid + Water ]       ===> Opaque Solid Suspension (Vigorous Continuous Agitation Required)

Operational Considerations for Flowables

• Agitation Requirements: Flowables require continuous, moderate-to-vigorous mechanical agitation throughout mixing and spraying. If tank agitation stops, the heavy solid particles rapidly settle to the bottom, forming a dense cake that is extremely difficult to re-suspend.
• Equipment Erosion: Because flowables contain abrasive solid particles suspended in liquid, they cause moderate-to-severe erosion of soft metal nozzle tips (such as brass and aluminum) and pump impellers under high pressure.
• Residue and Clogging: Flowables leave a visible powdery residue on treated foliage and structural surfaces. They can clog fine nozzle strainers (50-mesh or finer) if not properly diluted and agitated.
• Applicator Safety: Flowables eliminate the dust inhalation hazard associated with dry powders during tank loading, and they pose lower dermal absorption risks than solvent-based ECs.

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Microencapsulated Formulations (M or ME)

A Microencapsulated Formulation (M or ME) consists of a liquid or solid active ingredient encased in microscopic plastic, polymeric, or starch capsules suspended in a liquid carrier. After application to the target area, the polymer shell slowly breaks down, releasing the active ingredient over an extended time frame.

Key Advantages of Microencapsulation

• Extended Residual Control: Slow chemical release provides long-lasting pest control, reducing the frequency of required re-applications.
• Enhanced Applicator Safety: Enclosing the active ingredient within a polymeric shell significantly reduces acute dermal toxicity and odor during mixing and loading operations.

Critical Environmental Hazard: Honeybee Poisoning

The most significant drawback of microencapsulated formulations is their extreme hazard to foraging honeybees and beneficial pollinators. Microencapsulated spheres are manufactured in sizes ranging from 10 to 50 microns—matching the exact physical dimensions of natural pollen grains.

When foraging honeybees visit flowering plants or weeds in treated zones, static electricity on their body hairs attracts the microcapsules. The bees transport the capsules back to the hive, storing them alongside natural pollen as food for the brood. As young worker bees and larvae consume the contaminated pollen, the capsules rupture, delivering a lethal dose of pesticide that can destroy an entire bee colony.

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Ultra-Low Volume (ULV) Liquids

Ultra-Low Volume (ULV) formulations contain a very high concentration of active ingredient (often near 100%) dissolved in a specialized solvent. ULV products are designed to be applied at extremely low total spray volumes—typically less than 0.5 gallons per acre (and often as low as a few ounces per acre)—without water dilution.

Application Machinery and Primary Hazards

• Specialized Equipment: ULV applications require specialized aerosol generators, thermal foggers, or aerial spray equipment configured with high-speed rotary atomizers to create fine mist droplets (10 to 30 microns).
• Off-Target Drift Hazard: Because ULV spray droplets are micro-fine, these applications carry an extreme risk of off-target spray drift and atmospheric inversion movement. ULV applications must only be conducted under precise, calm atmospheric conditions.
• Applicator Health Hazards: High chemical concentration combined with micro-fine droplet size creates extreme dermal absorption and respiratory inhalation risks. Special protective equipment, including organic-vapor respirators and chemical-resistant coveralls, is mandatory.

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Comprehensive Summary of Liquid Formulations