Purdue Extension PPP-31

Pesticides and Formulation Technology Pesticides and Formulation Technology

Andrew Martin, Curriculum Development Specialist, Purdue Pesticide Programs Fred Whitford, Coordinator, Purdue Pesticide Programs Tom Jordan, Extension Weed Specialist, Purdue University

2 Pesticide Products and the Modern Marketplace ...... 4

An Overview of the Formulation Process...... 5

Formulation Selection Considerations ...... 6

Common Pesticide Formulations...... 7

Formulations and Label Information ...... 12

Synergists...... 13

Adjuvants...... 13

Summary...... 14

3 Pesticide Products and the Modern Marketplace

There is a seemingly endless Inert ingredients may be liquids variety of pesticide products into which the active ingredient is sold in the urban and dissolved, chemicals that keep the agricultural marketplace. product from separating or settling, Casual observation in any and even compounds that help hardware store or lawn secure the pesticide to its target and garden center will after application. reveal that variations The combination of an active extend even to products ingredient with compatible inert that are manufactured ingredients is referred to as a by the same chemical formulation. Pesticides are formulated company and contain for a number of different reasons. the same ingredients. A pesticide active ingredient in a Manufacturers often produce relatively pure form, ready for various forms of a pesticide to manufacturers’ use, rarely is suitable meet different pest control needs. for field application. An active For example, an insecticide may be ingredient usually must be formulated applied as a liquid to control adult in a manner that Japanese beetles on rose bushes and • Increases pesticide effectiveness as a solid material for suppressing in the field; the larval (grub) stage of that insect • Improves safety features; in turf. Applying the insecticide as • Enhances handling qualities. a liquid spray permits contact with The formulation gives the the adult beetle, while the solid form product its unique physical form can be watered into the root zone and specific characteristics, enabling of the lawn where the grubs live. it to fill a market niche. There are A pesticide product consists approximately 900 pesticide active of two parts: active and inert ingredients formulated into 20,000 ingredients. Active ingredients pesticide products sold and used in are chemicals which actually the United States today. For most control the pest. Inert ingredients practical purposes, the terms are primarily solvents and carriers formulation and product can that help deliver the active ingredients be used interchangeably. to the target pest; they serve to enhance the utility of the product.

4 An Overview of the Formulation Process

The active ingredients in pesticide detract from the pesticidal properties Suspension products come from many sources. of the active ingredient. A suspension is a mixture of finely Some, such as nicotine, pyrethrum, Usually, an active ingredient will divided, solid particles dispersed in and rotenone, are extracted from be combined with appropriate inert a liquid. The solid particles do not plants. Others have a mineral materials prior to packaging. A brief dissolve in the liquid, and the origin, while a few are derived review of some basic chemistry mixture must be agitated to from microbes. However, the vast terminology should prove helpful maintain thorough distribution. majority of active ingredients are in understanding differences among Most suspensions will have a cloudy synthesized (man-made) in the the various types of formulations. appearance. The herbicide Spike laboratory. These synthetic active 80W is formulated as a wettable ingredients may have been designed Sorption powder. This product forms a by an organic chemist or discovered In some cases it may be necessary suspension when mixed with through a screening process of or desirable to adhere a liquid active water for application as a spray. chemicals generated by various ingredient onto a solid surface (e.g., Label information describes the industries. a powder, dust, or granule). This need for sufficient agitation to Regardless of their source, process is called sorption and it can keep the product dispersed in pesticide active ingredients have be accomplished by two possible the spray tank. different solubilities. Some dissolve mechanisms: readily in water, others only in oils. • Adsorption—a chemical/physical Emulsion Some active ingredients may be attraction between the active An emulsion is a mixture that relatively insoluble in either water ingredient and the surface of occurs when one liquid is dispersed or oils. These different solubility the solid. (as droplets) in another liquid. characteristics, coupled with the • Absorption—entry of the active Each liquid will retain its original intended use of the pesticide, in ingredient into the pores of the identity and some degree of large measure define the types of solid. agitation generally is required to formulations in which the active keep the emulsion from separating. ingredient may be delivered. Solution Emulsions usually will have a It is preferable from the manu- A solution results when a substance “milky” appearance. The insecticide facturer’s perspective to use the (the solute) is dissolved in a liquid Demon EC is formulated as an active ingredient in original form, (the solvent). The solute can be a emulsifiable concentrate. The when possible (e.g., a water soluble solid or a liquid. The components active ingredient is dissolved in active ingredient formulated as a of a true solution cannot be me- an oil-based solvent. When the water soluble concentrate). When chanically separated. Once mixed, a product is mixed with water, an this is not feasible, it may become true solution does not require agita- emulsion is formed. An emulsifying necessary to alter the active ingredi- tion to keep its various parts from agent in the formulated product ent in order to change its solubility settling. Solutions are frequently helps prevent the emulsion from characteristics. This would be done, transparent. An example of a solu- separating by surrounding the obviously, in a manner that did not tion is the active ingredient in the oil droplets that contain the herbicide Roundup PRO: glyphosate dissolved active ingredient. (solute) dissolved in water (solvent).

5 Formulation Selection Considerations

The importance of formulation • Available equipment. Some pesticide type is generally overlooked. formulations require specialized A well-considered decision handling equipment. This includes to use the most appropriate application equipment, safety equip- formulation for a given ment, and spill control equipment. application will include an analysis of the • Surfaces to be protected. following factors. Applicators must be aware that certain formulations can stain • Applicator safety. fabrics, discolor linoleum, dissolve Different formulations plastic, or burn foliage. present various degrees of hazard to the applicator. • Cost. Product prices may vary Some products are easily inhaled, substantially, based on the ingredients while others can penetrate skin used and the complexity of delivering or cause injury when splashed in active ingredients in specific the eyes. formulations.

• Environmental concerns. Special Individuals such as commercial precautions need to be taken with pest control technicians or farm- formulations that are prone to drift workers who may not be involved in air or move off target into water. in the selection process but are Wildlife can also be affected to responsible for the actual application varying degrees by different also should be very aware of the formulations. Birds may be attracted type of formulation they are using. by granules, and fish or aquatic As stated, formulation type can invertebrates can prove especially have an impact on hazards to sensitive to specific pesticide human health and the environment. formulations. Inattention to the type of formulation being used could mean the difference • Pest biology. The growth habits between a routine application and survival strategies of a pest will and one that is the source of often determine what formulation environmental contamination— provides optimum contact between or worse, a serious human exposure. the active ingredient and the pest.

6 Common Pesticide Formulations

Formulations are classified as control outside. Commercial Dusts solids or liquids on the basis of their pest control operators use dusts physical state in the container at the effectively in residential and time of purchase. A formulation institutional settings for control can contain more than one active of various insect pests. Indoors, ingredient and many have to be this type of formulation permits further diluted with an appropriate the delivery of an insecticide carrier (e.g., water) prior to use. into cracks and crevices, behind baseboards and cabinets, etc. Solid Formulations Thus, the insecticide is placed Solid formulations can be divided into the pest’s habitat and away Granules into two types: ready-to-use; and from contact by people and pets. concentrates, which must be mixed with water to be applied as a spray. Granules The properties of six solid for- The manufacture of granular mulations are described in this formulations is similar to that publication. Three of the solid of dusts except that the active formulations (dusts, granules, and ingredient is sorbed onto a larger pellets) are ready-to-use, and three particle. The inert solid may be (wettable powders, dry flowables, clay, sand, or plant materials. and soluble powders) are intended A granule is defined by size: to be mixed with water. Granule-sized products will pass Pellets through a 4-mesh (number of wires Dusts per inch) sieve and be retained on Dusts are manufactured by the an 80-mesh sieve. Granules are and the difficulty inherent in sorption of an active ingredient applied dry and usually are intended achieving uniform application. onto a finely-ground, solid inert for soil applications where they have Granules also may have to be such as talc, clay, or chalk. They the advantage of weight to carry incorporated into the soil to work, are relatively easy to use because them through foliage to the ground and they are sometimes attractive to no mixing is required and the below. The larger particle size of nontarget organisms such as birds. application equipment (e.g., hand granules, relative to dusts, minimizes bellows and bulb dusters) is light- the potential for drift. There is also Pellets weight and simple. Dusts can a reduced inhalation hazard, but Pellets are very similar to granules, provide excellent coverage, but some fine particles are associated but their manufacture is different. the small particle size that allows with the formulation. The active ingredient is combined for this advantage also creates In addition, granules have a low with inert materials to form a slurry an inhalation and drift hazard. dermal hazard. The primary draw- (a thick liquid mixture). This slurry Dusts are generally applied as spot backs of granules are their bulk, the is then extruded under pressure treatments for insect and disease problems they present in handling, through a die and cut at desired

7 lengths to produce a particle that is disperse it throughout the tank. relatively uniform in size and shape. Wettable powders are a very common Pellets are typically used in spot type of formulation. They provide applications. Pelleted formulations an ideal way to apply (in spray form) provide a high degree of safety to an active ingredient that is not readily the applicator. They do have the soluble in water. Wettable powders potential to roll on steep slopes and tend to pose a lower dermal thereby harm nontarget vegetation hazard in comparison to liquid or contaminate surface water. formulations, and they do not burn vegetation as readily as oil-based Wettable Powders formulations. This formulation can Wettable powders are finely divided present an inhalation hazard to the solids, typically mineral clays, to applicator during mixing because of which an active ingredient is sorbed. the powdery nature of the particles. This formulation is diluted with Furthermore, there are a series of water and applied as a liquid spray. disadvantages associated with all The mixture forms a suspension in formulations that form a suspension the spray tank. Wettable powders in the spray tank: They require will likely contain wetting and agitation to prevent settling out; dispersing agents as part of the they can be abrasive to equipment; formulation. These are chemicals and they may cause strainers and used to help wet the powder and screens to plug.

Wettable powder before mixing

Wettable powder after mixing

8 Dry Flowables Dry flowables—or water dispersible granules, as they are sometimes called—are manufactured in the same way as wettable powders except that the powder is aggregated into granular particles. They are diluted with water and applied in a spray Dry flowable exactly as if they were a wettable powder. before mixing Dry flowables form a suspension in the spray tank; they have basically the same advantages and disadvantages as wettable powders, with several important excep- tions. During the mixing process, dry Dry flowable after mixing flowables pour more easily from the container and, because of their larger particle size, reduce inhalation hazard to the applicator. Note: The labels of some dry flowables do permit application of the product in the dry state.

Soluble Powders Soluble powders, although not particularly common, are worth mentioning in contrast with the wettable powders and dry flowables. Their lack of availability is due to the fact that not many solid active ingredients are soluble in water; those that do exist (formulated as soluble powders) are mixed with water in the spray tank, where they dissolve and Soluble powder form a true solution prior to spraying. before mixing Soluble powders provide most of the same benefits as wettable powders, without the need for agitation once dissolved in the tank. They are also Soluble powder after mixing nonabrasive to application equipment. Soluble powders, like any finely divided particle, can present an inhalation hazard to applicators during mixing.

9 Liquid Formulations potential problems inherent in any Emulsifiable Concentrates Descriptions of four common liquid suspension. However, they usually Emulsifiable concentrates consist formulations that are mixed with a do not require constant agitation of an oil-soluble active ingredient carrier follow. The carrier generally during application due to the dissolved in an appropriate oil-based will be water, but in some instances extremely small size of the suspended solvent to which an emulsifying labels may permit the use of crop oil, particles. One further problem noted agent is added. Emulsifiable or some other light fuel oil as a carrier. with this formulation is the difficulty concentrates are mixed with water in removing all of the product from and applied as a spray. As their Liquid Flowables the container during the triple name implies, they form an The manufacture of liquid flowables rinsing process. emulsion in the spray tank. (also called flowables or suspension The emulsifying agents allow concentrates) mirrors that of wettable Microencapsulates oil-soluble active ingredients to powders—with the exception that Microencapsulates consist of a solid be sprayed in water as a carrier. the powder, dispersing agents, or liquid inert (containing an active Some agitation is typically wetting agents, etc., are mixed with ingredient) surrounded by a plastic required to maintain dispersion water before packaging. The result or starch coating. The resulting of the oil droplets. They are not is a suspension requiring further capsules can be sold as dispersible abrasive to application equipment, dilution with water before use. The granules (dry flowables), or as a nor do they plug screens and product is applied as a spray, with all liquid formulation. Encapsulation strainers. Emulsifiable concentrates the advantages of a wettable powder. enhances applicator safety while have several disadvantages: They The benefit of this formulation is providing timed release of the present a dermal hazard; they that there is no inhalation hazard to active ingredient. Liquid forms can penetrate oily barriers like the applicator during mixing since of microencapsulates are further human skin; they usually have the powder already is suspended in diluted with water and applied as an odor problem; they can burn water, permitting it to be poured. sprays. They form suspensions in foliage; and they can cause the Liquid flowables form a suspension the spray tank and have many of the deterioration of rubber and plastic in the spray tank and have the same same properties as liquid flowables. equipment parts.

Liquid flowable Microencapsulate before mixing before mixing

Liquid flowable after mixing Microencapsulate after mixing

10 Solutions (RTU). This type of formulation ingredient to the target site in the Solutions (water-soluble concentrates) generally will have a low concentra- form of a mist of very small particles: consist of water-soluble active tion of active ingredient. Typically, solids or liquid drops. The particles ingredients dissolved in water, the container also serves as the can be released under pressure or for sale to the applicator for further application device. produced by fog or smoke generators. dilution prior to field application. Low and ultra low volume Aerosols are especially useful for They will obviously form a true (ULV) concentrates used in specialty indoor insect control, as coverage solution in the spray tank and situations (e.g., space spraying and is thorough. But it can be difficult require no agitation after they are fogging) are frequently applied to confine the aerosol to the target thoroughly dissolved. Solutions undiluted. Dermal hazards are a area, and there is always the danger are not abrasive to equipment and problem when mixing these products of inhalation. will not plug strainers and screens. because of the high concentration Fumigants deliver the active There are several major herbicides of active ingredient. Low and ultra ingredient to the target site in the with wide-scale use that are for- low volume concentrated formulations form of a gas. Some fumigants are mulated as solutions. They include utilize special equipment to deliver solids that turn into a gas in the products containing paraquat, the product in the form of very tiny presence of atmospheric moisture. glyphosate, and 2,4-D. Solutions droplets. Consequently, while they Others are liquids under pressure have few disadvantages; however, provide excellent coverage, drift that vaporize when the pressure is some that are produced as dissolved potential and inhalation problems released. Fumigants can completely salts can be caustic to human skin. during application can be quite high. fill a space, and many have tremendous penetrating power. They can be Miscellaneous Aerosols and Fumigants used to treat objects (e.g., furniture), Liquid Formulations Aerosols and fumigants are structures, grain, and even soil Most liquid formulations are frequently confused, yet they have for pest insects and other vermin. designed to be mixed with a carrier very different properties and uses. Fumigants are among the most before application. However, some Aerosols really refer to a delivery hazardous pesticide products to use products are sold ready-to-use system that moves the active due to their inhalation danger.

Emulsifiable Solution concentrate before mixing before mixing

Emulsion after mixing Solution after mixing

11 Formulations and Label Information

Product labels often will convey emulsifiable concentrate describes information about how the pes- the amount of active ingredient ticide is formulated by a suffix in the product on the basis of to the brand or trade name. pounds per gallon. The brand name The table below lists many Pendulum 3.3EC® indicates that of these suffixes and their the product is formulated as an meanings. A suffix can emulsifiable concentrate and that also include a number it contains 3.3 pounds of active that indicates the ingredient per gallon of product. amount of active Exceptions to these rules of thumb ingredient in the product. are common. Read the pesticide label The number contained in carefully for a precise description of the brand name suffix of a how the product is formulated. solid formulation such as a dust, granule, wettable powder, etc., describes the percent of active ingredient in that product on a Formulation Suffix percent by weight basis. For example, the brand Dust D name Tempo 20WP® Granule G tells the purchaser that the product is Pellet P, PS formulated as a wettable powder and Wettable Powder W, WP that it is 20 percent Dry Flowable DF active ingredient, by weight. The number Water Disperable Granule WDG included in the brand name suffix of a liquid Soluable Powder S, SP formulation such as a Liquid Flowable L, F liquid flowable or an Suspension Concentrate SC

Microencapsulate M

Emulsifiable Concentrate E, EC

12 Synergists Adjuvants

Synergists are chemicals that can An adjuvant is any compound that facilitates the action of boost the pesticidal activity of an pesticides or modifies characteristics of pesticide formulations active ingredient. The combination or spray solutions. The terminology for pesticide additives is of a synergist with the active confusing. It is often assumed that any material that lowers the ingredient provides a degree of surface tension of water (i.e., a surfactant) in the spray mixture pest control greater than what or increases the wettability of the spray solution on surfaces is would be expected from the simple an adjuvant. additive effects from each compound. Adjuvants are used in pesticide spray solutions as Synergists are used with a variety • Wetting agents • Co-solvents of pesticides including insecticides, • Penetrants • Stickers nematicides, and fungicides. • Spreaders • Stabilizing agents Synergists typically have little, It is obvious that the term adjuvant encompasses a wider if any, activity against the pest meaning than wetting agent or surfactant. There are many when used alone. However, EPA adjuvants that have little, if any, effect on pesticidal activity. policy is to include synergists in These types of adjuvants include the active ingredient statement • Anti-foam agents on the product label. • Buffering agents A common example of a synergist • Compatibility agents is piperonyl butoxide. This chemical • Drift control/deposition aids synergizes pyrethrin insecticides. Adjuvants are included in pesticide formulations as part of It is believed to function by slowing the total product which is sold by the manufacturer, or as an down the insect pest’s ability to additive to be mixed with pesticide products in the spray tank. metabolize (detoxify) pyrethrin, Adjuvants can be classified according to their type of action. resulting in fewer insects recovering There are three basic kinds: from exposure to the insecticide. • Activator adjuvants include surfactants, wetting agents, penetrants, and oils. Activator agents are the best known class of adjuvants because they are normally purchased separately by the user and added to the pesticidal solution in the spray tank. • Spray modifier agents include stickers, film formers, spreaders, spreaders/stickers, deposit builders, thickening agents, and foams. • Utility modifiers include emulsifiers, dispersants, stabilizing agents, coupling agents, co-solvents, compatibility agents, and anti-foam agents. Spray modifier agents and utility modifier agents usually are found as part of the pesticide formulation and thus are added to the pesticide product by the manufacturer.

13 Summary

The proper selection of a formulation is a critical step in any pest control process involving pesticides. It is an important management decision that has an impact on profitability, customer satisfaction, human safety, and environmental quality. An understanding of the properties of various formulations has as much significance to the applicator as it does to the supervisor. The applicator performs the duties of mixing as well as application. Applicators come into close contact with both the concentrated and diluted product. A simple, personal interest in one’s good health, and that of others, dictates the need to know the safety properties of the formulation being used. Furthermore, a concern for environmental quality reflected in a responsible application requires a familiarity with the attributes of a given formulation and the potential impact its use might have on the surroundings. Understanding the formulation allows one to maximize its benefits while reducing the risks.

14 A related publication for suggested reading: The Impact of Water Quality on Pesticide Performance (Purdue Extension publication PPP-86). It is available at: www pp. p pu. rdue ed. u/ Pubs/PPP-86 pd. f. Multiple copies may be ordered from the Purdue Extension Education Store: www ex. tension pu. rdue ed. u/store. Purdue Agriculture Revised 1/11

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