Choose Wisely For Pesticide Formulation Effectiveness

When a pesticide chemical is being manufactured, rarely can it be used in its raw or unformulated state, so the manufacturer must further modify the product by combining it with other materials such as solvents, wetting agents, stickers, powders, or granules. This combination of the product s active and inert ingredients is known as a formulation. Formulations allow for easier transportation and handling by your application equipment, and as an applicator, it’s your responsibility to choose the formulation wisely so that it will best meet your control requirements, be effective against the pest, and preserve the environment around you.


Interpreting an ingredient statement: Often the product name tells you something about the formulation. Below is an ingredient statement for the herbicide Buctril 4EC. However before looking at this statement, there are few important terms to I would like you to understand

Active Ingredient (AI): The active ingredient (a.i.) in a pesticide formulation is the actual chemical that controls the pest. When looking for the active ingredient look no further than the front label in the ingredient statement section just above the EPA registration number. It is a requirement by the EPA that the active ingredients are clearly stated on the label. Some products may contain one active ingredient while others may include several; however it’s important to understand that all active ingredients must be listed separately in the active ingredient statement.

Inert Ingredient: Inert ingredients are materials added during the formulation process to help stabilize the product. These ingredients are also added to help the product mix better with water, aid in transportation and handling while also assisting in the effectiveness and penetration of the product. The exact manufactures inert ingredients won’t be found on the label as these ingredients are trade secrets. What you will find in place of the exact inerts is “other ingredients” or” “inert ingredients “with a general explanation. Some of the different types of inerts may include water, emulsifiers, dye, surfactants, spreaders, stickers and wetting agents.

Phytotoxicity: Damage to a plant or plants resulting in over exposure to a pesticide.

Adjuvant: Adjuvants are substances that are used to aid in performance and at times are added directly into the product. Manufactures may also add adjuvants with the hope of creating a competitive edge. Adjuvants can also be added separately, if this is the case then they’re easily mixed into your tank along with the product just before treatment. Some of the common adjuvants include surfactants, emulsifying agents, wetting agents or spreaders, stickers, dyes and drift-control agents.

Now let’s take a look at the Buctril 4EC statement

Graphic for CEU Series #60
As you can see it contains the product name, the amount of active ingredient in pounds per gallon, and the type of formulation. In this instance the product name is Buctril, the amount of (a.i.) in pounds per gallon is 4, and the liquid formulation is EC meaning Emulsifiable Concentrate. Below that information you will find the actual active ingredient which in this case there are two, Octanoic acid ester of bromoxynil, and Heptanoic acid ester of bromoxynil, which make up 53% of the product. The inert ingredient is xylene range/petroleum distillates and as you can see the inert makes up 45%.

Below the inert ingredients section you will see that Buctril contains 4 pounds of active ingredient per gallon so if a container of this product amounted to two and a half gallons product, there would be 10 pounds of actual (a.i.) in the formulation.

Types of Formulations: Liquids

Emulsifiable Concentrates (EC): An emulsifiable concentrate will contain a liquid active ingredient, and one or more solvents. EC formulations will also contain an agent which allows the formulation when mixed with water to form an emulsion that will take on a characteristic milky color.

EC’s are used in a number of areas including agriculture, ornamentals, and turf. EC’s are also used for control of interior and public health pests. Advantages of EC’s include easy handling, transportation and storage. Other advantages are your application equipment nozzles will not clog, along with EC’s not leaving residues on treated surfaces.

A major disadvantage is toxicity to humans as EC’s can easily be absorbed through the skin. For this reason alone always read the Personal Protection Equipment portion of the label to determine what protective equipment must be worn when mixing, loading and applying. Other disadvantages include mixing and calibration requirements and the ability of EC’s to deteriorate metal and rubber, while also being flammable. When mixing be extremely careful with your calibration, as high active ingredient concentrations can cause damage or phytotoxicity to desirable plants.

Solutions (S): There are some pesticide active ingredients that are manufactured to dissolve readily in a liquid such as water or petroleum-based solvent. These solutions are either in the form of a concentrate which must be diluted further, or as a ready- to- use formulation. These types of solutions when mixed with the carrier will dissolve and not settle out or separate. Glysophate the active ingredient in number of herbicides is a good example of a solution. Advantages to using a solution is they are easy to handle, no agitation is required, and is easy on your equipment. Solutions leave little residue and can be used indoors or outdoors. About the only disadvantage is that there is limited number of formulations of this type available.

Ultra-Low Volume (ULV): Ultra-low volume formulations are most commonly used outdoors in specific situations such as mosquito control and require specialized application equipment. ULV’s are diluted with small amounts of a specific carrier or used without any dilution at all. For this reason ULV’s are used at very low rates often times not exceeding one half pound per acre. ULV’s require specialized equipment so it can be applied in small droplets at very low volumes. As an applicator it is important to pay attention to wind speed as ULV applications have a high potential for drift.

ULVs have similar advantages to emulsifiable concentrates and soluble liquids, in that they are easy to transport, handle, and store, remain in solution and require little or no agitation. ULV’s are not abrasive on equipment leave little residue, and will not clog screens or nozzles. Drift hazard due to the small mist-like droplets is significant which makes ULV’s difficult to keep on site. ULV’s require specialized equipment and have solvents in the formulation that will erode rubber, nylon, and plastic. Careful calibration of your equipment and paying attention to wind speed are the two most critical factors as is you’re applying a highly concentrated form in small droplet size.

Invert Emulsions: An Invert emulsion is comprised of a water-soluble pesticide, and utilizes oil not water as the carrier for the tank mix. As a result, the tank mixture will be comprised of heavy amounts of oil with very little water. Because the mixture is heavily oil-based it becomes very thick causing spray-droplets to be large and heavy. With predominantly water based formulations, drift is a greater possibility because the water droplets evaporate before reaching the target. Since the size and weight of the invert emulsion droplets are oil based, their susceptibility to evaporation is less, thus their ability to drift off target site is greatly reduced. This is why invert emulsions are most commonly used in areas where drift is susceptible to non-target plants and areas that are environmentally sensitive. Invert Emulsion will also improve surface coverage and absorption because they act as a sticker-spreader. This addition not only s aids in the reduction of polluted storm water runoff, it helps detracts from Invert Emulsions ability to wash away in the event of rain.

Flowables (F)/Liquids (L): A flowable or liquid formulation is similar to an emulsifiable concentrate and wettable powder. These formulations are used when the active ingredient is a solid that will not dissolve in either water or oil. When manufacturing these formulations, the active ingredient is first fused onto a material such as clay, and then finely ground into a powder. The powder is suspended in small amounts of liquid resulting in a product that is very thick. Flowables share many of the same attributes as an emulsifiable concentrate including ease of application and handling.

Disadvantages of flowables include a tendency to settle out, so moderate agitation is needed to keep them in suspension. Because these products do have a tendency to settle out, manufactures package them in 5 gallon containers to make it easier for the applicator to remix. Another disadvantage is that flowables can cause wear and tear on your nozzles and pumps.

Aerosols (A), and liquid Baits: Most aerosol formulations contain one or two small amounts of active ingredient which are usually packaged with an inert gas in a pressurized can that when activated by the trigger valve release a fine mixture of aerosol droplets. Aerosol containers are very convenient and are most often used in hard to reach areas in commercial buildings, and residential homes. There are also electrical or gasoline powered generators that dispense aerosols. These are very specialized pieces of commercial equipment which also produces a fine mist and can hold 5 to 10 pounds of a refillable pesticide. Because a fine mist is released with both types of application techniques, be cautious with aerosols as they can easily cause applicator exposure and are subject to drift.

Advantages of ready-to-use aerosols include one or more active ingredients packaged in a ready-to-use pressurized container. Other advantages of aerosols include they are ready to use, portable, easy to store, and will not lose their strength over a long period of time. Aerosols are available in small amounts and are convenient and economical to purchase. Disadvantages include limited use, risk of oral exposure, dangerous if punctured or overheated, or used near an open flame. Aerosols are also difficult to keep on the target site or pest.

Liquid Baits: Liquid baits are used mostly by structural pest control operators. These products are formulated as liquids and are very effective especially against rodents. The liquid bait is mixed with water then placed in station. This method is particularly effective in areas where rodents can’t find water. Liquid baits are also used in controlling certain species of sugar feeding ants. Sugar feeding worker ants will consume the bait and then feed it directly to the queen and young in the nest. There are species of ants that prefer to feed on gel baits. One disadvantage of liquid baits is they must be replaced often.

As you can see there are a number of liquid formulations available to you for pest control. Remember as an applicator you must choose the formulation that will best meet your requirements for your particular job.

Considerations in making a choice include effectiveness against the pest, habits of the pest, the plant, animal or surface to be protected, application equipment, danger of drift and runoff, and possible injury to the protected surface. With that in mind let’s now turn our attention to dry or solid formulations.

Dry or Solid Formulations

Baits (B) Baits: are formulated by combining an active ingredient, along with food and an attractant. Pests are killed by eating the bait which has the pesticide concealed within it. Baits are used inside of structures and are strategically placed to control ants, roaches, and rodents. Baits are also used in the landscape to control slugs, snails, and insects such as ants and roaches. The active ingredient in baits is nominal usually less than 5 %.

Baits are convenient as they are packaged as a ready to use product, and baits can be placed strategically so an entire area does not have to be treated. This makes it convenient if the pests are migrating in and out of an area you are attempting to control. However be very cautious where you place the baits as they can be attractive to both children and pets. Also when using baits you need to realize that there is no control of where the pest will die which can lead to a pest order problem. It is important to replenish baits and remove old stations because as the active ingredient wears off the bait itself can become a source of food.

Pastes (P) / Gels (GL): Today, pastes or gels are preferred by the pest control industry as these products have little order, are easy to place, and present a slight chance of exposure to humans. Pastes and gels do have a tendency to melt out. Be careful with repeated applications as you can stain a porous surfaces so be sure to clean up previous applications.

Dusts (D): Dust formulations are convenient as they are packaged as a ready – to –use product. Dusts can be very effective in hard to reach areas such as cracks and crevices especially when trying to control ants and cockroaches. Dusts contain around a 10% active ingredient by weight. In addition to the active ingredient, dusts have a very fine inert carrier made from either talc, chalk, clay, nut hulls, or volcanic ash with the active ingredient then stuck to the outside of the particle. Dusts require simple application equipment however be aware that dampness can cause clogging, and lumping. Dusts work by the pest ingesting the poisonous material while they are grooming or through absorption by the outer body as they track across the dust. Careful application is paramount as dusts can easily drift off target site by air or be moved by water. As an applicator be sure to wear the appropriate PPI as dusts can irritate eyes, nose, throat and skin.

Granules (G): Granular formulations are not much different the than dusts with the exception of them being larger and heavier. These course materials are made from clay, corncobs, or walnut shells. The active ingredient is very low extending from less than 1 to 15 percent and either coats the outside of the granule or is imbibed into it. Granules are mostly used to control weeds, nematodes, and insects in the soil. Granules also aid in the control of larval mosquitoes and other aquatic pest. Granules can be used in a wide range of situations including agriculture, structural, turf and ornamental, aquatic, and public health.

Unlike dusts the drift potential for granules is low as particles will settle quickly. Other advantages include no mixing, slight hazard to the applicator because of little dust or no spray, the weight carries the material through the foliage and to the soil, can easily be applied by fertilizer spreaders, and the material is slowly released. Difficulties include equipment calibration, application uniformity, and granules have worked into the soil, and need moisture to activate the pesticide which becomes a problem in drought conditions. An environmental concern when applying granules is that they can be eaten by water fowl because of their seed-like appearance.

Pellets (P): Pellet formulations are similar to granular formulations and actually the terms are often interchangeable. The big difference is that pellets are consistently the same size and weight which allows for greater application precision.

Wettable Powders (WP or W): Wettable powders are dry, finely ground formulations that are easy to store and fairly easy to measure and mix. WP’s are usually mixed with water and must constantly be kept in a state of agitation to keep the suspended particles from settling out. Before adding WP’s to a tank mix you will need to know the Ph of your water as powders can be difficult to dilute in high Ph or alkaline water. Wettable powders can be quite abrasive to pumps and cause significant wear in nozzles constructed of soft metals. They leave visible residues when they dry which can be a problem on ornamental plants in high traffic areas. You should wear a dust mask when measuring and mixing as the concentrated powder can be easily inhaled. WP’s can often clog equipment nozzles and screens.

Soluble Powders (SP or WSP): Soluble powders resemble wettable powders. However, when you mix a soluble powder with water it easily dissolves creating a true solution. This is a benefit to the applicator because as long as the powder is thoroughly mixed , no additional agitation is necessary. There are not a great deal of soluble powders available on the market because few active ingredients are readily soluble in water. Soluble powders are easy to measure/mix, have a high percentage active ingredient, have little phytotoxicity concerns, and are less absorbed by human skin and eyes. However be careful of inhalation.

Water-Dispersible Granules (WDG) or Dry Flowables (DF): WDG’s granules are also go by the name of dry flowables. They resemble wettable powders except instead of being dust like they are formulated as small, easy to measure granules. Before applying WDG’s you must first mix them with water. Once mixed in water the granules dissolve into a fine powder. Because the granules do dissolve into a fine powder, constant agitation is required. The percentage of active ingredient can be as high a 90 percent by weight in these formulations.

Other Formulations

Microencapsulated Materials (M or ME): When pesticide companies manufacture a microencapsulated formulation they encapsulate a liquid or dry pesticide particle in plastic coating. This formulation is mixed with water and as the coating dissolves the active ingredient is released. One benefit of encapsulated materials is that the water-soluble packets reduce human exposure during mixing and applying. However, microencapsulated materials offer a specific hazard to bees. Because the microcapsules are similar in size to pollen grains, foraging bees can carry the microencapsulated materials back to their hives. As the capsules begin to break down, the pesticide is released, poisoning the colony.

Microencapsulated material release is weather dependent resulting in slower breakdowns. The slower breakdown has the potential to leave higher residues of active ingredients on the on the plant material which intern can interferes with the restricted entry time period and the harvest interval. For this reason, regulations require a long restricted-entry or harvest interval because of the potential to injure farm workers.

Water – Soluble Packets (WSB or WSP): Water-soluble packets are packets containing a precise amount of several different formulations in a special bag that is dropped into the spray tank with the water. The pesticide is slowly released into the tank as the bag dissolves. Water-soluble packets reduce human exposure during mixing and handling, as there are no risks breathing in or contacting the undiluted pesticide, providing the bag is not opened or damaged. Remember once the mix is diluted you must be careful with application as the solution is no safer than other diluted pesticides.

Attractants: Attractants are used in a number of ways and can include pheromone traps, sugar, protein syrups, and yeasts. The use of pheromone traps can indicate the type and amount of insects currently near or around your plants providing you with the means to make a sound economic spray decision. Trapping can also help indicate the best possible time to spray for maximum effectiveness. There are other attractants that can be combined with the active ingredients to control your pest problems. Ant baits for instance contain sugars, proteins, oils, or a combination of these as attractants along with the active ingredient. Liquid yeast can be used as fly baits.

Impregnated Products: Flea and tick collars, cattle ear tags, plastic resin pest strips and other products are all examples of impregnated pesticide formulations. These products emit a vapor that controls a pest nearby, however over time as the vapors dissolve they lose their efficacy. Some fertilizers are impregnated with a pesticide, if this is the case; it is wise to treat the product as you would a pesticide, which means paying attention to application and storage. Some paints and wood finishes have pesticides incorporated into them to kill insects or retard fungal growth.

Repellents: People apply repellents to their skin as either an aerosol or a lotion formulation. You can mix other types of repellents with water and spray them onto ornamental plants and agricultural crops to prevent damage from deer, dogs, and other animals.

Pesticide/Fertilizer Combinations: Combining insecticides, fungicides, and herbicides with a fertilizer product is a very convenient way of controlling pests while fertilizing crops or lawns. Homeowners commonly use these combinations to control insects and weeds. The unit cost for these products is high however that cost can be recouped by the amount of time it would take to apply the combined products separately.

Fumigants: Fumigants are pesticides that form gases or vapors toxic to plants, animals, and microorganisms. Some active ingredients are formulated, packaged, and released as gases, while others are packaged as liquids under high pressure and change to gases when they are released. Fumigants are used for structural pest control, in food and grain storage facilities, and in regulatory pest control at ports of entry and at state and national borders. In agricultural pest control, fumigants are used in soil, greenhouses, granaries, and grain bins.

Combining Pesticides

There may be a time when you want to combine and apply two or more pesticides plus fertilizer for either convenience, to save money, or to reduce equipment wear. When you do combine ingredients you are creating what is known as a tank mix. Tanks mixes can consist of a fungicide and an insecticide to control both a fungus and insects at the same time. Sometimes you may want to mix a pesticide with fertilizer, or mix two herbicides together to increase weed control. Tank mixes save time, labor, money, equipment wear, and crop damage. However if you mix with Improper combinations you can cause phytotoxicity to crops or ornamental plants, damage equipment and in the long run spend more money.

When choosing to tank-mix various chemicals, the applicator should always be aware of which pesticides can and can’t be mixed. You can find this information on the label in what is called a pesticide label compatibility chart. So read the label after all it is the law! However, unless expressly prohibited by a pesticide’s label, mixing is legal.

There may be times when you want to mix more than two active ingredients or confirm that two different inert ingredients such as emulsifiers and wetting agents will mix properly. If this is the case you must take precautions as pesticide label compatibility charts usually refer to only two pesticide active ingredients. So how do you know if the pesticide formulations you want to mix are compatible or not?

Compatibility Testing

When pesticides don’t mix together properly or will not form a uniform solution the formulations you have combined are considered incompatible. Incompatible solutions will end up with flakes, crystals, oily clumps or noticeable separation. Another symptom of incompatible solutions will be heat generating from the mixture. When a solution is incompatible it will clog nozzle heads, limit distribution uniformity of the active ingredient, costing you valuable time and money. Impurities in your spray tank, the order in which you mixed the pesticides, the types of formulations being mixed water temperature, and the amount of time the mixture has sat in the tank are reasons for incompatibility to occur.

The 2-Jar Test for Compatibility

A sure fire way to insure the formulations you are mixing are compatible is to use a standard 2-jar compatibility test. By using two jars for mixing various pesticides and fertilizers, you can determine compatibility before you tank mix. When performing compatibility tests, remember you must wear the personal protective equipment listed on the most restrictive label.

1. Measure 1 pint of carrier (water or liquid fertilizer) to each of 2 quart jars.

2. Add ¼ teaspoon of compatibility agent to one jar, but not the second jar (equivalent to 2 pints per 100 gallons of spray solution). Compatibility agents are adjuvants used to reduce incompatibility (lack of mixing) of pesticides or pesticide and liquid fertilizer mixtures. Types of compatibility agent products include Blendex® and Unite®.
3. Wettable powders, water dispersible granules, and dry flowables: add 1 tablespoon for each pound per 100 gallons of final spray mixture. Shake slightly to simulate agitation.
4. Water-soluable concentrates, solutions, and flowables add 1 teaspoon for each pint per 100 gallons of final spray mixture. Shake slightly to simulate agitation.
5. Emulsifiable concentrates: add 1 teaspoon for each pint per 100 gallons of final spray mix. Shake slightly to simulate agitation.
6. Soluble powders: add 1 teaspoon for each pint per 100 gallons of final spray mix. Shake slightly to simulate agitation.
7. Remaining adjuvants: add 1 teaspoon for each pint per 100 gallons of final spray mixture. Shake slightly to simulate agitation.
8. After 15 minutes of letting the jars stand, feel the sides of the jars to check for heat emission. If so, a chemical reaction may be occurring, indicating incompatibility. Let the mixture stand another 15 minutes and check again for heat.
9. After standing for 30 minutes, compare the component of the 2 jars and decide:
a. Jar with no compatibility agent has dispersed ingredients with no flaking, layer separation, formation of gels, etc., then the mixture is compatible and no compatibility agent is necessary.
b. Compare with jar that contains compatibility agent.
c. If the components are not dispersed in either jar, the pesticide-carrier mixture is not compatible and should not be used.


There are a many types of pesticide formulations, and although they are formulated differently they all contain an active and inert ingredient. Active ingredients function as the pesticide intended to control the pest, with the inert ingredient acting as the carrier. When looking at a label’s ingredient statement, you will always find the active and inert ingredients plus the formulation. To better understand which formulation is best for your application needs it is important to know the different types of formulations and how they work. Remember before mixing pesticides you must always read label instructions carefully to be sure if the active ingredients and the formulation types are compatible. If the label doesn’t cover compatibility of the products you want to mix, then you must perform a 2-jar test for compatibility.

As a pesticide applicator you must take into consideration several factors when deciding what type of pesticide formulation to use. These factors will include not only human and environmental exposure but also which formulation is best for the target site and pest you are trying to control. By having a basic understanding of these factors you as a pesticide applicator will be able to choose wisely for pesticide formulation effectiveness.