Pesticide Formulations
Introduction
The active ingredients in a pesticide are the chemicals that control the target pest. Most pesticide products you buy also have other ingredients, called inert (inactive) ingredients. They are used to dilute the pesticide or to make it safer, more effective, easier to measure, mix, and apply, and more convenient to handle.
Usually the pesticide is diluted in water, a petroleum-based solvent, or another diluent. Other chemicals in the product may include wetting agents, spreaders, stickers, or extenders. This mixture of active and inert ingredients is called a pesticide formulation.
Some formulations are ready for use. Others must be further diluted with water, a petroleum-based solvent, or air (as in airblast or ULV applications) by the user before they are applied. A single active ingredient often is sold in several different kinds of formulations. If you find that more than one formulation is available for your pest control situation, you must choose the best one for the job.
Liquid Formulations
Emulsifiable concentrates (EC or E)
An emulsifiable concentrate formulation usually contains liquid active ingredient, one or more petroleum-based solvents, and an agent that allows the formulation to be mixed with water to form an emulsion.
Advantages:
- Relatively easy to handle, transport, and store,
- Little agitation required -- will not settle out or separate when equipment is running,
- Not abrasive,
- Do not plug screens or nozzles,
- Little visible residue on treated surfaces.
Disadvantages:
- High concentration makes it easy to overdose or underdose through mixing or calibration errors,
- May cause unwanted harm to plants,
- Easily absorbed through skin of humans or animals,
- Solvents may cause rubber or plastic hoses, gaskets, and pump parts and surfaces to deteriorate,
- May cause pitting or discoloration of painted finishes,
- Flammable -- should be used and stored away from heat or open flame,
- May be corrosive.
Solutions (S)
Some pesticide active ingredients dissolve readily in a liquid solvent, such as water or a petroleum-based solvent. When mixed with the solvent, they form a solution that will not settle out or separate. Formulations of these pesticides usually contain the active ingredient, the solvent, and one or more other ingredients.
Advantages:
- No agitation necessary.
Disadvantages:
- Limited number of formulations of this type available.
Ultra-low-volume (ULV)
These concentrates may approach 100 percent active ingredient. They are designed to be used as is or to be diluted with only small quantities of specified solvents.
Advantages:
- Relatively easy to handle, transport, and store,
- Little agitation required,
- Not abrasive to equipment,
- No plugging of screens and nozzles,
- Little visible residue on treated surfaces.
Disadvantages:
- Difficult to keep pesticide in the target site -- high drift hazard,
- Specialized equipment required,
- Easily absorbed through skin of humans or animals,
- Solvents may cause rubber or plastic hoses, gaskets, and pump parts and surfaces to deteriorate.
Flowables (F or L)
Some active ingredients are insoluble solids. These may be formulated as flowables in which the finely ground active ingredients are mixed with a liquid, along with inert ingredients, to form a suspension. Flowables are mixed with water for application and are similar to EC or wettable powder formulations in ease of handling and use.
Advantages:
- Seldom clog nozzles,
- Easy to handle and apply.
Disadvantages:
- Require moderate agitation,
- May leave a visible residue.
Aerosols (A)
These formulations contain one or more active ingredients and a solvent. Most aerosols contain a low percentage of active ingredient. There are two types of aerosol formulations -- the ready-to-use type, and those made for use in power aerosol generators.
Advantages of ready-to-use formulations:
- Ready to use,
- Easily stored,
- Convenient way to buy small amount of a pesticide,
- Retain potency over fairly long time.
Disadvantages of ready-to-use aerosols:
- They are practical for very limited uses,
- Risk of inhalation injury,
- Hazardous if punctured, overheated, or used near an open flame,
- Difficult to confine to target site or pest.
Advantages of power aerosol generators:
- Easy way to fill entire space with pesticide.
Disadvantages of power aerosol generators:
- Highly specialized use and equipment,
- Difficult to confine to target site or pest,
- May require respiratory protection to prevent risk of inhalation injury.
Dry Formulations
Dusts (D)
Most dust formulations are ready to use and contain a low percentage of active ingredient (usually 1/2 to 10 percent), plus a very fine dry inert carrier made from talc, chalk, clay, nut hulls, or volcanic ash. The size of individual dust particles is variable. Dusts are always used dry, and they easily drift into nontarget sites.
Advantages:
- Usually ready to use, with no mixing,
- Effective where moisture from a spray might cause damage,
- Require simple equipment,
- Effective in hard-to-reach indoor areas.
Disadvantages:
- Easily drift off target during application,
- Residue easily moved off target by air movement or water,
- May irritate eyes, nose, throat, and skin,
- Do not stick to surfaces as well as liquids,
- Difficult to get an even distribution of particles on surfaces.
Baits (B)
A bait formulation is an active ingredient mixed with food or another attractive substance. The bait either attracts the pests or is placed where the pests will find it. Pests are killed by eating the pesticide the bait contains.
Advantages:
- Ready to use,
- Entire area need not be covered, because pest goes to bait,
- Control pests that move in and out of an area.
Disadvantages:
- Can be attractive to children and pets,
- May kill domestic animals and nontarget wildlife outdoors,
- Pest may prefer the crop or other food to the bait,
- Dead pests may cause odor problem,
- Other animals may be poisoned as a result of feeding on the poisoned pests.
- If baits are not removed when the pesticide becomes ineffective, they may serve as a food supply for the target pest or other pests.
Granules (G)
Granular formulations are similar to dust formulations except that granular particles are larger and heavier. The coarse particles are made from an absorptive material such as clay, corn cobs, or walnut shells. The active ingredient either coats the outside of the granules or is absorbed into them.
Granular formulations also are used to control larval mosquitoes and other aquatic pests. Granules are used in agricultural, structural, ornamental, turf, aquatic, right-of-way, and public health (biting insect) pest control operations.
Advantages:
- Ready to use -- no mixing,
- Drift hazard is low, and particles settle quickly,
- Little hazard to applicator -- no spray, little dust,
- Weight carries the formulation through foliage to soil or water target,
- Simple application equipment, such as seeders or fertilizer spreaders,
- May break down more slowly than WP's or EC's through a slow-release coating.
Disadvantages:
- Do not stick to foliage or other nonlevel surfaces,
- May need to be incorporated into soil or planting medium,
- May need moisture to start pesticidal action,
- May be hazardous to nontarget species, especially waterfowl and other birds that mistakenly feed on the grain- or seed-like granules.
Wettable powders (WP or W)
Wettable powders are dry, finely ground formulations that look like dusts. They usually must be mixed with water for application as a spray. Wettable powder particles do not dissolve in water. They settle out quickly unless constant agitation is used to keep them suspended.
Advantages:
- Easy to store, transport, and handle,
- Less likely than EC's and other petroleum-based pesticides to cause unwanted harm to treated plants, animals, and surfaces,
- Easily measured and mixed,
- Less skin and eye absorption than EC's and other liquid formulations.
Disadvantages:
- Inhalation hazard to applicator while pouring and mixing the concentrated powder,
- Require good and constant agitation (usually mechanical) in the spray tank and quickly settle out if agitation is turned off,
- Abrasive to many pumps and nozzles, causing them to wear out quickly,
- Difficult to mix in very hard or very alkaline water,
- Often clog nozzles and screens,
- Residues may be visible.
Soluble powders (SP or WSP)
Soluble powder formulations look like wettable powders. However, when mixed with water, soluble powders dissolve readily and form a true solution. After they are mixed thoroughly, no additional agitation is necessary. Soluble powders have all the advantages of wettable powders and none of the disadvantages except the inhalation hazard during mixing.
Microencapsulated pesticides (M)
Microencapsulated formulations are particles of pesticides (liquid or dry) surrounded by a plastic coating. The formulated product is mixed with water and applied as a spray. Once applied, the capsule slowly releases the pesticide. The encapsulation process can prolong the active life of the pesticide by providing a timed release of the active ingredient.
Advantages:
- Increased safety to applicator,
- Easy to mix, handle, and apply,
- Releases pesticide over a period of time.
Disadvantages:
- Constant agitation necessary in tank,
- Some bees may pick up the capsules and carry them back to their hive where the released pesticide may poison the entire hive.
Adjuvants
An adjuvant is a chemical added to a pesticide formulation or tank mix to increase its effectiveness or safety. Most pesticide formulations contain at least a small percentage of adjuvants. Some of the most common adjuvants are surfactants -- "surface active ingredients" that alter the dispersing, spreading, and wetting properties of spray droplets.
Common adjuvants are:
- Spreaders -- allow pesticide to form a uniform coating layer over the treated surface.
- Stickers -- allow pesticide to stay on the treated surface.
- Foaming agents -- reduce drift.
- Thickeners -- reduce drift by increasing droplet size.
- Buffers -- allow pesticides to be mixed with diluents or other pesticides of different acidity or alkalinity.
Authors:
Philip G. Koehler, University of Florida
Robert A. Belmont, Florida Pest Control Association
This file is part of the UF/IFAS Basic Pesticide Training manual (SM-59) which is intended to provide intermediate training to pest control operators. The manual was adapted from a larger manual, Applying Pesticides Properly, which was developed by Ohio State University in cooperation with the Cooperative Extension Service, U.S. Department of Agriculture, and the Office of Pesticide Programs, U.S. Environmental Protection Agency.
Published: March, 1998
