CHAPTER 4

Pesticide Formulations

LEARNING OBJECTIVES

After studying this chapter, you should be able to: • Describe what a pesticide formulation is. • Explain why pesticides are formulated for end use. • Distinguish between active and inert ingredients. • State the meaning of abbreviations used for common types of formulations (e.g., WP). • List the factors to consider when choosing a formulation for a specific site or situation. • Discuss the properties of common formulations. • Evaluate the advantages and disadvantages of the formulations described in this chapter. • Explain the roles of adjuvants.

pesticide formulation is a com- as diluents or carriers. In many cases, A bination of active and inert inert ingredients make the formulated ingredients that forms an end-use product safer, easier to handle and pesticide product. Pesticides are for- apply, and/or more effective. mulated to make them safer or easier So, in addition to the active ingre- to use. This is because many pesticide dient intended to control the target pest, active ingredients, in “pure” (technical a formulated product may consist of: grade) form, are not suitable for appli- cation. In their concentrated form, • A carrier or diluent, such as an some are extremely toxic, many do not organic solvent of mineral clay. mix well with water, some are unstable, • Surface-active ingredients, such and some are difficult (or unsafe) to as stickers and spreaders. handle, transport, or store. To address these problems, manufacturers add • Other additives, such as sta- inert ingredients to end-use pesticide bilizers, dyes, and chemicals, products. Inert ingredients have no pes- which make the product safer or ticidal activity, and some simply serve enhance pesticidal activity.

PESTICIDE FORMULATIONS 49 FORMULATIONS: AN OVERVIEW

he active ingredients in pesticide A suspension is also a liquid Tproducts come from many sources. mixture. However, a suspension is Some, such as azadirachtin, pyrethrum, formed by dispersing fine (very small), and rotenone, are extracted from plants. solid particles in a liquid. These solid Others are derived from microbes or particles do not dissolve in the liquid insects (e.g., Bacillus thuringiensis and carrier. Suspensions must be agitated to insect growth regulators). Still others maintain uniform particle distribution. have a mineral origin (e.g., copper and Otherwise, the undissolved parts of sulfur). However, the vast majority suspension mixtures will settle (or of active ingredients used today are float to the top). Most suspensions are produced in laboratories. These syn- cloudy or opaque: they will not allow thetic active ingredients may have been light to pass through them. Pesticide designed by a chemist or discovered products formulated as suspensions through screening processes by exam- are not water-soluble; they form more ining chemicals generated by various dilute suspensions when mixed with industries or found in nature. water to make a finished spray. Label Regardless of where they come directions for suspension formulations from or how they are produced, will instruct you to shake well before pesticide active ingredients vary con- measuring and mixing. The label will siderably in their physical and chemical further state to apply these products properties. One variable is solubility. only with spray equipment that has Some dissolve in water, but many do enough agitation to keep the final not. Some are soluble in oils or organic mixture evenly distributed in the spray solvents. However, many such solvents tank during application. A mixture of are not available to applicators or safe to flour and water is an example of a sus- use. A few active ingredients do not dis- pension. solve readily in any solvent. Solubility An emulsion is a special kind of sus- and the intended use of the pesticide pension: a mixture made by suspending are two factors that determine how an droplets of one liquid in another. Each active ingredient is formulated (i.e., ingredient retains its unique properties made into an end-use product). and identity. To make an emulsion, an Liquid pesticide products are active ingredient is dissolved in an oil- usually one of the following: based solvent and then further diluted • A solution. with water. Some agitation may be necessary to keep an emulsion from • A suspension. separating. However, most emulsion • An emulsion. pesticide product formulations have additives (emulsifiers or emulsifying A solution is made by dissolving a agents) that prevent the product from substance in a liquid. A true solution is settling. As a rule, emulsions have a a mixture, but it cannot be separated by “milky” appearance. An emulsifiable filtration or other mechanical means. concentrate (E or EC) is an emulsion. Once made, a true solution will not Homogenized milk is an example of an “settle out” and does not need shaking emulsion. or stirring (agitation) to keep the mixed Most dry products are made by components in solution. Solutions are adhering the active ingredient to some transparent: they will allow light to solid carrier, such as talc, clay, silica (the pass through them. (However, this may mineral quartz), or plant residues (e.g., not be obvious if one or more compo- ground corncobs). nents of the mixture are dark in color Some pesticide products are sold in and the solution is very concentrated.) concentrate form and must be mixed or Sweetened iced tea and saltwater are diluted before use. Concentrates come examples of solutions. in both liquid and solid form. An emul-

50 CHAPTER 4 sifiable concentrate is an example of a Abbreviations in trade or brand liquid concentrate (LC). Wettable pow- names are often used to describe the ders (WP), soluble powders (SP), and formulation (e.g., WP for wettable water-dispersible granules/dry flowables powders), how the pesticide is used (e.g., (WDG/DF) are examples of concen- TC for termiticide concentrate), or the trated materials sold in solid form. characteristics of the formulation (e.g., Other formulations are sold ready- LO for a low-odor formulation). The to-use. You can apply ready-to-use amount of active ingredient (a.i.) and products with no further dilution or the kind of formulation are listed on the mixing. Examples include liquids pre- product label. Numbers in a product’s pared as end-use dilutions and aerosol trade or brand name may also indicate (A), dust (D), pellet (P), granule (G), the amount of active ingredient it con- and most bait (B) formulation products. tains. For example, 80 WDG indicates Manufacturers package many spe- that this dry product contains 80% cialized pesticides, including products by weight of active ingredient and is a intended for residential uses by non- water-dispersible granule. In this case, occupational users, in ready-to-use a 10-pound bag of product contains formulations. 8 pounds of a.i. and 2 pounds of inert Concentrates are often less ingredient. Liquid formulations usually expensive per treatment/unit area state the amount of a.i. in pounds per treated than ready-to-use formula- gallon. For example, 4F means 4 pounds tions. However, this cost savings may of the a.i. per gallon in a flowable for- be offset by other considerations. For mulation. Some common formulation example, concentrates are usually more abbreviations are listed in Table 4.1. toxic than dilute formulations of the A single active ingredient is often same active ingredient. More handling sold in several kinds of formulations. is required to mix and load them. As a Below is a short description of common result, concentrates present a higher formulations, along with the pros and exposure risk to the user. cons of each. If more than one formu-

Table 4.1 Abbreviations for Common Formulations

A = Aerosol PS = Pellets AF = Aqueous flowable RTU = Ready-to-use B = Bait S = Solution C = Concentrate SP = Soluble powder (or soluble packet; D = Dust see WSP) DF = Dry flowables (see WDG) ULV = Ultra-low volume E = Emulsifiable concentrate W = Wettable powder EC = Emulsifiable concentrate WDG = Water-dispersible granules (see DF) F = Flowable WP = Wettable powder G = Granules WS = Water soluble GL = Gel WSB = Water-soluble bag (see WSP: L = Liquid water-soluble packet) LC = Liquid concentrate WSC = Water-soluble concentrate LV = Low volatile WSL = Water-soluble liquid M = Microencapsulated WSP = Water-soluble powder (or water- P = Pellets soluble packet; see WSB)

PESTICIDE FORMULATIONS 51 lation is available for your pest control • Do I have the necessary appli- site and situation, choose the best one cation equipment? for the job. Base your decision on: • Can the formulation be applied • Legal, labeled uses. appropriately under the condi- • The signal word. tions in the application area? • Applicator safety. • Will the formulation reach the intended target and stay in • Environmental safety. place long enough to control • Pest biology. the pest? • Site characteristics. • Is the formulation likely to damage the surface? • Target (surface to be treated). • Appropriate and available appli- • Could I choose a less hazardous cation equipment. formulation that would still be as effective? Ask yourself these questions: Cost is always a consideration, but • Is the intended use listed on the pesticide and pest management con- product label? cerns should come first.

LIQUID FORMULATIONS

ost liquid formulations are diluted are used against pests in agricultural, Mwith water to make a finished spray. ornamental and turf, forestry, struc- However, some labels direct users to mix tural, food processing, livestock, and the product with another solvent such as public health settings. ECs are adapt- crop oil or other light oil as a carrier. able to many types of application equip- ment, from small, portable sprayers to Emulsifiable Concentrates hydraulic sprayers, low-volume ground (E or EC) sprayers, mist blowers, and low-volume An emulsifiable concentrate for- aircraft sprayers. mulation usually contains an oil-soluble Advantages: liquid active ingredient, one or more petroleum-based solvents, and a mix- • Relatively easy to handle, ing agent. The mixing agent allows the transport, and store. formulation to be mixed with water • Easy to pour and measure. to form an emulsion. Most ECs con- tain between 2 and 6 pounds of active • Little agitation required; will ingredient per gallon. ECs are among not settle out or separate when the most versatile formulations. They equipment is running. • Not abrasive; does not cause excessive equipment wear. • Will not usually plug screens or nozzles. • Leave little visible residue on treated surfaces.

d applicators d use only by certifie For retail sale an of and only e direct supervision Disadvantages: or persons under th plicatorís d by the certified ap for those uses covere certification. • High concentration of active ingredient(s) makes it easy to ooi kfhksiusj overdose or underdose through mixing or calibration errors.

52 CHAPTER 4 • May damage treated plants or RTU products are produced for pest surfaces (petroleum-based sol- management professionals (who treat vents or overdosing may cause structural and institutional pests) and phytotoxicity). for nonoccupational users. • Easily absorbed through skin of Advantages: humans or animals. • Convenient; neither measuring • Splashes and spills are relatively nor mixing is required. difficult to clean up and/or • Some are packaged and sold in— decontaminate. or with—an application device. • Many have a strong odor. If this is the case, no loading is required. • Solvents may cause equipment “wear and tear.” For example, • Less personal exposure risk due rubber or plastic hoses, gaskets, to reduced toxicity and handling. pump parts, and other exposed Disadvantages: surfaces may deteriorate. • Limited availability. • May cause pitting or discolor- ation of painted finishes or other • High cost per unit of active treated surfaces. ingredient. • Flammable; should be used and The time saved and convenience of stored away from heat or open using RTU products may outweigh the flame. product cost. • May be corrosive. Concentrate Solutions (C, LC, or WSC/WSL) Solutions (S) Other solutions are available as Some pesticide active ingredients concentrates that require dilution with dissolve readily in a liquid solvent, such a liquid solvent before you apply them. as water or a petroleum-based diluent. Often the solvent is water, but it may When mixed, they form a solution also be a refined oil or petroleum-based that does not settle out or separate. solvent. When diluted with the label- Formulations of these pesticides usually specified carrier, these formulations contain the active ingredient, solvent form true solutions. (carrier or diluent), and one or more other ingredients. Solutions are suit- Advantages: able for any type of sprayer, indoors or outdoors. Consequently, they are reg- • Relatively easy to handle, trans- istered for many sites, including struc- port, and store; easy to pour and tural, institutional, public health, and measure. household pest control; livestock and • No agitation necessary. poultry pest management; space sprays in barns and warehouses; and treatment • Not abrasive; do not cause of food and fiber crops, turf, and orna- excessive equipment wear. mental plants. • Do not plug screens or nozzles. Ready-to-Use (RTU) • Do not usually leave visible Low-Concentrate Solutions residues on treated surfaces. Ready-to-use formulations require Disadvantages: no further dilution before application. • Limited availability, especially They consist of a small amount of water-based solutions. active ingredient (often 1% or less per unit volume). Some ready-to-use • Spills and splashes may be products contain petroleum-based difficult to clean up and/or solvents; others are water-based. Many decontaminate.

PESTICIDE FORMULATIONS 53 • Some are easily absorbed Disadvantages: through skin of humans or • Not all ants, cockroaches, and animals. rodents will feed on liquid baits. The other benefits and draw- • You must refill or replace backs of concentrated solutions vary. liquid-containing bait stations They depend on the concentration of frequently. active ingredient, solvent or diluent used, application site, and application For information about solid-for- equipment. mulation baits, refer to “Baits” in the “Dry or Solid Formulations” section. Liquid Baits Some insecticides and rodenticides Ultra-Low Volume are now formulated as liquid baits. Most Ultra-low-volume concentrates liquid insecticides are concentrated have almost 100% active ingredient. sugar solutions. They are packaged in They are designed to be used “as is” ready-to-use bait stations to kill ants or diluted with only small quantities and cockroaches. of specified solvents. These special- As a rule, liquid rodenticide baits purpose formulations are most suitable are mixed with water and placed in spe- for outdoor applications, such as in cially designed bait stations. They are agricultural, forestry, ornamental, useful in sites where sanitation is poor and mosquito control programs. because traditional food-based baits ULV products are applied as very fine “compete” with other food sources. As droplets at very low rates per unit area is the case with solid baits, you must (or volume). place bait stations in safe, strategic loca- tions while following label directions Advantages: and taking care to protect children and • Relatively easy to handle, nontarget organisms. transport, and store. Advantages: • Little or no agitation required. • Liquid ant baits are very useful • Not abrasive to equipment. in controlling sugar-feeding • Do not plug screens and nozzles. ants. • Leave little visible residue on • Ants that will feed on liquid baits treated surfaces. carry this material to the colony. Disadvantages: • Liquid rodenticide baits will often control rodents in areas • High drift hazard due to small where food is abundant, but water droplet size. is scarce or lacking altogether. • Specialized equipment required. • Easily absorbed through skin of humans or animals; high dermal and inhalation exposure risk (concentrated product applied as fine droplets). • Products and/or solvents may cause rubber or plastic hoses, gaskets, and pump parts and other surfaces to deteriorate. OPEN CLOSED • Calibration and application must be performed with special A bait station used in rodent control in the closed and open positions. care because ULV products are Bait formulations are placed inside the tamper-resistant station. applied in concentrated form.

54 CHAPTER 4 Invert Emulsions lation is a flowable. However, some use Invert emulsions contain a water- the letter “L,” meaning that an insoluble soluble pesticide dispersed in an oil car- material is presented in “liquid” form.) rier. These products require a special Most flowables are prepared by first kind of emulsifier that allows the pes- impregnating them onto a dry carrier, ticide to be mixed with a large volume such as clay. Then, the active ingredi- of petroleum-based carrier, usually fuel ent plus carrier (or the active ingredient oil. Invert emulsions are less susceptible alone) are ground into a fine powder. to drift because oil evaporates more Next, the fine powder is suspended in a slowly than water. When applied on a very small amount of liquid (and perhaps hot, dry day, a water-based droplet will other inert ingredients). The resulting become smaller as the water portion product is a thick liquid suspension. of the droplet evaporates. Invert emul- Flowables combine many of the sion droplets do not “shrink” as rapidly characteristics of liquid emulsifi- when applied in the same weather con- able concentrates and dry wettable ditions. This means less drift and more powders. They appear in the “Liquid pesticide on target. Invert emulsions are Formulations” section because the end- thick mixtures, with the consistency of use product is a thick liquid. Flowables mayonnaise. In addition, invert emul- are often used for the same types of pest sions are applied as very large droplets, control operations as ECs. which reduce drift. Advantages: The oil phase of this kind of formulation also serves as a sticker- • Easy to handle and apply; low spreader. This quality improves rainfast exposure risk. properties and surface coverage. It also increases absorption and/or penetra- • Generally not phytotoxic. tion. This, in turn, reduces loss due to • Seldom clog nozzles. runoff. Invert emulsions are relatively uncommon. They are most often used • Splashes are less likely than with in weed control on rights-of-way to other liquid formulations. reduce the chance of drift to susceptible nontarget plants or sensitive areas. Disdvantages: Advantages: • May settle; need shaking before measuring and mixing. • Low drift. • Difficult to remove all of product • Increased rate of penetration from the container. Containers and/or absorption. may be difficult to rinse. • Increased rainfastness and reduced runoff. • Require moderate agitation. Disadvantages: • May be abrasive; contribute to “wear and tear” of spray appli- • Difficult to treat the underside of cation equipment. foliage or other targets because droplets are large and heavy. • Spills may be harder to clean up. • Limited availability. • May leave a visible residue on treated surfaces. Flowables (F or AF) Some active ingredients are in- Aerosols (A) soluble solids: substances that will not Aerosol formulations contain one dissolve in either water or oil. These or more active ingredients and a solvent. may be formulated as flowables. (Most Most aerosols contain a low percentage manufacturers use the letter “F” by the of active ingredient. There are two trade name to designate that the formu- types of aerosol formulations:

PESTICIDE FORMULATIONS 55 • The ready-to-use type (often • Hazardous if punctured, over- sold in pressurized sealed con- heated, or used near an open tainers that serve as application flame. devices). • May be difficult to direct • Those made for use in electric or material released to a single gasoline-powered aerosol gener- target site or pest. ators that release the formulated product as a smoke or fog. Formulations for Smoke or Fog Generators Ready-to-Use Aerosols Formulations for smoke or fog gen- erators are not packaged and sold under Ready-to-use aerosol formulations pressure. They are used in machines are usually small, self-contained units that break the liquid formulation into that release pesticide when the nozzle a fine mist or fog (aerosol). Using a valve is triggered. An inert pressurized rapidly whirling disk or heated surface, gas pushes the pesticide through a fine the machines produce and distribute opening when the gas is released, cre- very fine droplets. These formulations ating fine droplets. These products are are used mainly for insect control in effective in greenhouses, in small areas structures such as greenhouses, barns, inside buildings, or in localized outdoor and warehouses and for outdoor mos- areas. Commercial models, which hold quito and biting fly control. 5 to 10 pounds of pesticide, are usually refillable. Advantages: Advantages: • Easy way to fill an entire space with pesticide. • Easy to use; convenient. • Portable. Disadvantages: • Easily stored. • Highly specialized use sites and equipment. • Convenient way to buy and apply • Difficult to confine to target site a small amount of pesticide. or pest. • Retain potency for some time. • Spills and splashes may be Disadvantages: difficult to clean up and/or decontaminate. • Practical for only a few limited or specialized uses. • May require respiratory pro- tection to prevent inhalation • Risk of inhalation exposure. exposure.

DRY OR SOLID FORMULATIONS

here are two general types of dry Tformulations. Some are ready-to- use. Others are concentrates, which must be mixed with water and applied as a spray. Dusts (D) Most dust formulations are ready- to-use and contain a low percentage of active ingredient (usually 10% or less by weight). A few dust formulations, however, are concentrates and contain

56 CHAPTER 4 a much higher percentage of active Advantages: ingredient. These concentrates must • Usually ready-to-use; no be mixed with dry inert carriers before mixing. application. Dusts have one or more active • A good alternative where ingredients plus a very fine, dry inert moisture from a spray carrier made from talc, chalk, clay, might cause damage. nut hulls, or volcanic ash. The size of • Applied with simple individual dust particles varies, but all application equipment. Arlene Blessing, are quite small. Due to their small size, Purdue Pesticide Programs dusts need careful handling to prevent • Effective in hard-to-reach nontarget exposure, including drift. indoor areas. They are not water-soluble. Therefore, Disadvantages: do not mix them with a liquid solvent. Dusts are always used dry. They • Easily drift off target during Dust formulations are often used as seed treatments and application. are always used dry. in some other agricultural operations. • Residues do not adhere to treated Some ornamental and garden pest man- surfaces, including foliage, as agement products aimed at homeowners well as liquids do; may easily are dust formulations. In structures, wash off or blow away. dust formulations are useful to treat cracks and crevices and for spot treat- • May irritate eyes, nose, throat, ments to control insect pests. Dusts are and skin; pose a relatively high also a good tool to control lice, fleas, inhalation exposure risk to han- and other external parasites on pets and dlers. livestock. • Dampness may cause product to Special dusts known as tracking clump and equipment to clog; powders are effective for insect and difficult to apply in damp or rodent monitoring and control. These humid environments. products are finely ground dusts with an adsorbed stomach poison. Insects • Some kinds of application and rodents walk through the dust, pick equipment and devices are hard it up on their legs and bodies or feet to calibrate. and fur, and ingest the poisonous dust • Difficult to get an even distri- when grooming. Tracking powders are bution of particles. effective in sites and situations where bait acceptance is poor (for example, Granules (G) where food is abundant). NOTE: Another option is to use Granular formulations are similar a nontoxic powder, such as talc or flour, to dust formulations; however, granular to monitor and track rodent activity in particles are larger and heavier. Like buildings. dusts, they are not water-soluble. They are ready-to-use–not intended to be mixed with water and applied as a liquid suspension. The coarse particles that serve as carriers for granular formula- tions are adsorptive substances like clay or absorptive plant material such as ground corncobs or walnut shells. The active ingredient either coats the outside of the granules or is absorbed into them. The amount of active ingre- dient is relatively low, usually ranging from 1% to 15%. A bulb duster used for applying dust Because many granular formula- formulations to cracks, crevices, and tions use carriers that absorb moisture, voids in buildings. humidity will affect particle size and

PESTICIDE FORMULATIONS 57 mass. This, in turn, will affect flow • Application equipment is not as rate. Also, different “batches” convenient to calibrate as spray of the same formulation equipment. Released particles may differ slightly in size are measured by weight instead or shape and density. of by volume. For these reasons, you • Uniform application may be dif- must calibrate granu- ficult with some devices (e.g., lar application devices rotary spreaders). often. Arlene Blessing, O nc e appl ie d , • Granules do not stick to foliage Purdue Pesticide Programs granules slowly release or other uneven surfaces. For the adsorbed or absorbed this reason, contact products are active ingredient. Some rarely formulated this way. require soil moisture, rain, or • May need to be incorporated watering to initiate the release of into soil or planting medium. Granular formulations the active ingredient. Other granules are larger and heavier do so as they decompose. • May need moisture to release than dust formulations. Granular pesticides are mostly the active ingredient; may not be used to apply chemicals to the soil, effective in drought conditions. where they control weeds, nematodes, • May be hazardous to nontarget and insects or are absorbed by plant species, especially waterfowl and roots. Most granular formulations are other birds. This is because birds used to deliver systemic pesticides. may feed on grain- or seed-like Granules are a common choice in many granules or mistake them for sites and situations. “grit” they need to grind up Aerial applicators sometimes use their food. granular formulations to reduce drift or penetrate dense vegetation. Granular • Bulky; low percentage of active formulations are also useful in aquatic ingredient per unit volume. situations to control mosquito larvae and aquatic weeds. Pellets (P or PS) Advantages: Most pellet formulations are very similar to granular formulations in their • Ready-to-use; no mixing. uses, advantages, and disadvantages. • Drift hazard is low, and particles However, in pellet formulations, all settle quickly. the particles are more or less the same weight and shape. They are produced • Low applicator hazard: no spray; by combining the active ingredient little dust. with inert materials to form a “slurry” • Weight carries the —a thick liquid mixture. This mixture formulation through is then extruded under pressure. As a foliage to soil or water result, pellets are round in cross section target. and cut to a specific length. Because pellet particles are more uniform, you • Applied with simple can apply them with precision. However, application equipment, in many cases, pellets are applied as spot such as seeders or treatments. A few fumigants are formu- Arlene Blessing, fertilizer spreaders. lated as pellets and are clearly labeled Purdue Pesticide Programs • May break down more as such to avoid confusing them with slowly than WPs or nonfumigant pellets. ECs because of a slow-release coating. Wettable Powders (WP or W) Wettable powders are dry, finely Disadvantages: In pellet formulations, ground solid materials. Most include all particles are the same • Application equipment needs wetting and/or dispersing agents. weight and shape. frequent calibration. Usually, they must be mixed with water

58 CHAPTER 4 and applied as a spray. A few products, • Abrasive to pumps however, may be applied dry or as a and nozzles; cause liquid suspension. equipment wear. Wettable powders contain 5% to 95% active ingredient—usually 50% • Difficult to mix or more. Wettable powder particles do in very hard or not dissolve in water. When mixed with very alkaline water, they form a suspension. They water. will settle out quickly without constant • If not mixed Arlene Blessing, agitation to keep them suspended. properly, may Purdue Pesticide Programs To prepare a spray suspension, you clog nozzles and must form a slurry. Mix a WP with a screens. small amount of water, and then dilute this slurry mixture further. • Residues may be visible Wettable powders are effective for on treated surfaces. most pest problems and in most types Wettable powders of spray equipment where agitation is Water-Dispersible Granules are dry, finely ground formulations that look possible. They have excellent residual (WDG) or Dry Flowables (DF) activity and do not usually harm treated like dusts. surfaces. When you apply a WP spray Water-dispersible granular formu- suspension to a target, most of the lations are wettable powder formulations pesticide remains on the surface. This compressed into dust-free, granule- is true even for porous materials, such sized particles. Most come with a prod- as concrete, plaster, and untreated uct-specific measuring device, with wood. In such cases, only the water dry ounce (or pound) increment marks carrier penetrates the porous material. based on product density (weight per Wettable powder particles remain on unit volume). Because of this and the the treated surface. fact that they readily flow or pour out of their containers, they are easier to Advantages: measure and cleaner to handle than WPs. Like wettable powders, water-dis- • Easy to store, transport, and persible granules are mixed with water handle. and applied as a spray suspension. Once • Less likely than ECs and other in water, the granules break apart into petroleum-based formulations fine powder. The formulation requires to harm treated plants, animals, constant agitation to keep it suspended and surfaces. in water. Water-dispersible granules Arlene Blessing, Purdue Pesticide Programs share the advantages and disadvantages • As a rule, not phytotoxic. Water-dispersible of wettable powders. However, WDGs granule before mixing. • Less risk of skin and eye have one added benefit: reduced handler absorption than ECs and other exposure risk. This is because WDGs/ liquid formulations. DFs are: Disadvantages: • Made of larger, less “dusty” particles. • Not easy to measure; must be weighed. • Easier to remove from their con- tainer and measure. • Not easy to mix. • Inhalation hazard to applicator Soluble Powders (SP or WSP) while measuring and mixing the Soluble powder formulations look concentrated powder. like wettable powders. However, when • Suspended particles require good mixed with water, soluble powders dis-

and constant agitation (usually solve readily in water and form a true Arlene Blessing, Purdue Pesticide Programs mechanical) in the spray tank solution. After a thorough mixing, no and quickly settle out if agitation additional agitation is necessary. The Water-dispersible ceases. amount of active ingredient in soluble granule after mixing.

PESTICIDE FORMULATIONS 59 powders ranges from 15% to 95%; may serve as a food supply for it usually is more than 50%. Soluble the target pest or other pests. powders have all the advantages of WPs but only one of the disadvantages: • May not work in situations where inhalation hazard during mixing. Not pests have many other food or many pesticides are available in this water sources. formulation because very few active ingredients dissolve in water. For information about liquid baits, see “Liquid Formulations” above. Baits (B) Pastes, Gels, and Other A bait formulation is an active Injectable Baits ingredient mixed with food or another attractive substance. The bait either Pastes and gel baits are mainly attracts the pests or is placed where used in the pest control industry for the pests will find it. Many baits are ants and cockroaches. In fact, insecti- solid (blocks, granules, or pellets), but cides formulated as pastes and gels are some are liquids, pastes, or gels. The now the primary formulations used in amount of active ingredient in most cockroach control. They are designed bait formulations is quite low, usually to be injected or placed as either a bead less than 5%. or dot inside small cracks and crevices Baits are used inside buildings of building elements where insects to control ants, cockroaches, flies, tend to hide or travel. Two basic types and other insects. Outdoors, they of tools are used to apply pastes and can control vertebrate pests, such as gels: syringes and bait guns. The bait rodents, other mammals, and birds as is forced out of the tip of the device well as snails, slugs, and some insects. by applying pressure to a plunger or Applicators must place bait stations in trigger. safe, strategic locations while following label directions to protect children and Advantages: nontarget organisms. • Odorless; no vapors. Advantages: • Low human toxicity. • Ready-to-use. • Last for long periods.

For retail o sale an r perso d use o ns un nly by for t der th certif hose u e direc ied ap ce ses co t supe plicat rtifica vered rvision ors • Entire area need not be covered tio by o n. the ce f and rtified only appli cator’s • Low applicator exposure risk. because pest goes to bait. • Hidden placements minimize • Control pests that move in and human and pet exposure. out of an area. • Very accurate in their placement Disadvantages: and dosage. A bait gun used by the • May be attractive to children pest control industry to • Easily placed where insects shelter and pets. treat small cracks and for maximum effectiveness. crevices. • May kill domestic animals and nontarget wildlife. Disadvantages: • Require careful placement and • Can become contaminated from inspection. exposure to other pesticides and cleaning products. • Pest may prefer the crop or other food to the bait. • When exposed to high tempera- tures, gels can run and drip. • Dead vertebrate pests may cause odor problems. • May stain porous surfaces. • If baits are not removed after the • Repeated applications can cause pesticide stops working, they an unsightly buildup.

60 CHAPTER 4 OTHER FORMULATIONS

his section describes other formula- • May require the use of Ttions that: specialized application Fumigant equipment. • Are not easily classified as liquid or dry/solid. • Some have specific tem- • Are formulated and/or applied as perature requirements. gases. • Have some special packaging or Microencapsulated delivery method. Pesticides (M) Microencapsulated pesticides are Fumigants are packaged Fumigants dry particles or liquid droplets sur- in liquid and solid forms. rounded by a coating. Coatings may Both turn into poisonous Fumigants are pesticides that gases when applied. deliver the active ingredient to the target be plastic, starch, or some other mate- site in the form of a gas. Some active rial. Microencapsulated pesticides are ingredients are liquids when packaged mixed with water and applied as a spray. under high pressure but become gases Once applied, the pesticide is released when released. Other active ingre- from the capsule. In some situations, dients are volatile liquids. They may the encapsulation process can pro- be enclosed in an ordinary container vide “timed” slow release of the active and not packaged under pressure. Still ingredient. Depending on the physi- others are solids that release gases after cal properties of the coating, release application in humid conditions or in of the pesticide active ingredient may the presence of water or water vapor. be weather-dependent. If the release is Fumigants are used for structural pest slower than normal (for example, due control, in food- and grain-storage to dry or cool weather), residues may facilities, and in regulatory pest control remain on treated plants or surfaces at ports of entry and state and national longer than expected. As a result, borders. In agricultural pest control, some microencapsulated products have fumigants are effective in soil, green- relatively long restricted-entry or pre- houses, and commodity storage areas harvest intervals. (such as grain bins). Some microencapsulated pesticide products contain highly toxic materi- Advantages: als with a coating to increase handler safety. Others are microencapsulated • Toxic to a wide range of pests. for different reasons; for example, to • Can penetrate cracks, crevices, reduce staining or odor or to protect wood, and tightly packed areas the active ingredient from photodegra- (such as soil or grains). dation. Highly toxic microencapsulated pesticides may be very hazardous to • A single treatment will usually kill bees if the particles do not break down most pests in the treated space. quickly and are the same size as pollen Disadvantages: grains. Foraging bees may collect them and carry them back to the hive. Later, • The target site must be enclosed when the coatings break down and or covered to prevent the gas release the pesticide, the colony may from escaping. be poisoned. Some microencapsulated • Nonspecific and highly toxic to soil-applied products may be more humans and all other organisms. prone to leaching. • High inhalation exposure risk. Advantages: • Most require the use of specialized • Coatings help protect the personal protective equipment. applicator.

PESTICIDE FORMULATIONS 61 • Easy to mix, handle, and apply. Advantages: • Timed release of active ingre- • Accurate premeasured unit doses. dient prolongs effectiveness (i.e., • Increased handler safety; greatly may result in fewer applications; reduced exposure risk. application timing may be less critical). • Lower risk of spills. • Reduced volatility. Disadvantages: • Package size may not match vol- • Reduced odor. ume of prepared solution needed • Less likely to stain or otherwise and/or spray tank volume. damage treated surfaces. • May not be suitable for products • Reduced phytotoxicity. applied in pounds or gallons of active ingredient per acre, due Disdvantages: to the size or number of packets required. • Constant agitation may be nec- • Must be kept dry—away from essary in spray tank (depending water or high humidity—until on the properties of the coating). ready to use. • Risk of injuring or killing bees (if the microencapsulated product Impregnates is toxic to them). Some pesticide products consist of a pesticide active ingredient incorpo- • Long restricted-entry or pre- rated into a solid material, usually some harvest intervals for highly toxic kind of plastic. The pesticide evapo- products. rates or is released over time, and the vapors control nearby pests. Common Water-Soluble Packaging examples include: (WSB or WSP) • Livestock ear tags. More and more pesticide prod- • Plastic pest strips and adhesive ucts are available in water-soluble bags tapes. (WSBs). A special film packages a pre- • Pet collars. cise amount of wettable powder, solu- ble powder, or gel containing the Fertilizers may also be impreg- pesticide active ingredient(s). nated with pesticides. When added to water in a spray tank, the bag dis- Animal Systemics solves and releases the contents, which then Animal systemics are absorbed by, are suspended or dis- enter the tissues of, and move within the solved. This packag- treated animal. Usually, these pesticides M.J. Weaver, M.J. Weaver, ing method reduces are applied externally or orally. They can h a nd ler e x p o s u re control fleas and other external blood- feeding insects as well as worms and Virginia Tech Pesticide Programs Virginia Tech risk. It also simplifies measuring. However, other internal parasites. External appli- water-soluble packaging cation methods include pour-on liquids, is just that—as a rule, it will sprays, and dusts. Oral applications not dissolve in organic solvents or include food additives and premeasured capsules, pastes, or liquids. Adding water-soluble undiluted ECs. As a result, mixers and packet to a spray tank. loaders must follow label instructions Pesticide-Fertilizer when preparing a spray mixture. Store water-soluble products in a dry place, Combinations and do not handle them with damp or Many pesticide products—usually wet gloves. granule and pellet formulations—are

62 CHAPTER 4 combinations of fertilizers and pesti- homeowners commonly use these for cides. Such products are convenient their lawns. Dealers or growers may because they allow the applicator to custom mix pesticides with fertilizers to control pests and apply nutrients at meet specific crop requirements. the same time. Some are prepackaged:

PESTICIDE MIXTURES

ometimes, product manufacturers the number of weed species controlled Scombine pesticides with other (control spectrum). However, products pesticides or fertilizers for sale as must be compatible in order to be tank- premixes (see “Pesticide-Fertilizer mixed. Combinations” above). However, when Federal law allows applicators to premixes are not available (or are not combine pesticides unless the labeling offered in the desired combination), of one or more components of the you may combine products at the time intended tank mix specifically prohibits of application. Tank mixing—com- it. If no prohibitions exist, applicators bining two or more crop-production may mix: products (pesticides and/or fertilizers) and applying them at the same time—is • Pesticide with fertilizer. convenient and cost-effective. This • Two or more pesticides. practice can save the time, labor, fuel, and equipment wear involved in mul- When pesticides are tank-mixed, Edward Maryland Crow, Department of Agriculture tiple applications. Tank mixing also all of the dosages must be at or below reduces soil compaction and the risk of the label rate for each separate com- mechanical damage to crops or treated ponent of the mixture. Incompatibility is a areas. Situations appropriate for tank For more information about the condition that prevents mixing include combining fungicides causes and effects of incompatibility, pesticides from mixing and insecticides to treat fruit trees or how to do a compatibility test, and how together properly to field crops. Another common example to prepare a tank mix, see Chapter 10, form a uniform solution is combining herbicides to increase Planning the Pesticide Application. or suspension.

ADJUVANTS

n adjuvant is a chemical that ize the product or formulation for spe- Acan affect how a pesticide works. cific needs or to compensate for local Adjuvants: conditions. Because adjuvants lack pesticidal • Improve the action of a pesticide. properties, the U.S. Environmental • Change the characteristics of a Protection Agency does not register pesticide formulation or a spray them. As a result, there are no standards mixture (suspension or solution). for composition, quality, or perfor- mance. If you have questions about an Most end-use pesticide products, adjuvant, contact the manufacturer. especially those that are applied to Companies that produce these products foliage, contain adjuvants. However, in can provide labels, technical data sheets, some situations, applicators may add Safety Data Sheets (SDSs), supplemen- them to a tank mix when making a tal labeling, and promotional literature. finished spray mixture. Many adjuvants Before using any adjuvant, con- increase effectiveness and/or safety. sult the pesticide product label. Some Although they enhance the action of a products have very specific adjuvant pesticide or modify the properties of a recommendations or prohibitions. If a spray solution, adjuvants alone have no label instructs you to use an adjuvant, pesticidal activity. Use them to custom- use the type called for at the directed

PESTICIDE FORMULATIONS 63 rate. As noted, many products already etrate) the outer surface to the contain those adjuvants deemed neces- inside of treated foliage. Certain sary or useful by the manufacturer or plant penetrants may increase formulator. Adding others may actually penetration on some—but not decrease efficacy or result in unintended all—plant species. —and possibly undesirable—effects. • Safeners—reduce the toxicity of a pesticide formulation to Types of Adjuvants the pesticide handler or to the There are many types of adjuvants. treated surface. Here are some that are commonly used: • Spreader—allow pesticide to • Antifoaming (defoaming) agents form a uniform coating layer —reduce foaming of spray mix- over the treated surface. tures that may result from using • Stickers—allow pesticide to stay some surfactants and/or from on a treated surface. Some types vigorous agitation. of stickers increase adhesion • Buffers or pH modifiers—allow of solid particles to a treated TYPES OF pesticides to be mixed with dilu- surface. This reduces the ents or other pesticides of dif- amount of pesticide that washes ADJUVANTS ferent acidity or alkalinity. Most off due to rain or irrigation. Surfactants pesticide solutions or suspensions Others reduce evaporation and/ are stable between pH 5.5 and 7.0 or slow photodegradation. (See Wetting agents (slightly acidic to neutral). Water “Extenders” above.) and spreaders outside this range may cause pes- • Surfactant—see “Surfactants” ticides to degrade—very rapidly, Stickers below. Extenders in some cases. If you use a buffer, add it to the spray tank water first • Thickeners—increase viscos- Plant penetrants and mix well. The water must be ity (thickness) of spray mix- Compatibility pH neutral or slightly acidic to tures. Thickeners may reduce agents start, before adding pesticides or drift and/or slow evaporation. Buffers or pH other adjuvants. (Slowing evaporation is useful when applying systemic pesti- modifiers • Compatibility agents—help com- cides. It increases the time dur- bine pesticides (or pesticides and Drift retardants ing which the active ingredient fertilizers) effectively; reduce or can be absorbed by or penetrate Defoaming eliminate incompatibility. agents plant foliage.) • Drift control additives (deposition Thickeners • Wetting agents—allow wettable aids)—reduce drift; increase powders to mix with water. average droplet size and/or lower the number of “fines” (very small droplets) produced. Surfactants Some of the most common adju- • Emulsifiers—allow petroleum- vants are surfactants (surface active based pesticides (ECs) to mix ingredients), which alter the dispersing, with water. spreading, and wetting properties of • Extenders—keep pesticides spray droplets. Examples of surfactants active on a target for an extended are wetting agents and spreaders. These period. Some adjuvant manufac- products physically change the surface turers use this name for stickers. tension of a spray droplet. In order to (See “Stickers” below.) perform well, some pesticide sprays must be able to wet treated foliage • Invert emulsifiers—allow water- thoroughly and evenly. Surfactants that based pesticides to mix with reduce surface tension enable droplets petroleum carrier. to spread out instead of bead up. This • Plant penetrants—allow the results in better coverage and increases pesticide to pass through (pen- the odds that the pest will contact the

64 CHAPTER 4 pesticide. Surfactants are particularly • Read and follow the label. Is helpful when treating plants with waxy an adjuvant recommended? If or hairy leaves (see Figure 4.1). so, what type? Do not make Surfactants are classified by how substitutions. Note that some they split apart into charged atoms or product labels may recommend molecules, called ions. an adjuvant for one type of use or site but prohibit any kind of • Anionic surfactants have a adjuvant for another labeled negative charge. They are most use or site. Many end-use for- often used with contact pesti- mulated products already have cides, which control the pest by adjuvants, and adding adju- direct contact instead of being vants “on the fly” can decrease absorbed systemically. efficacy. Suppose, for example, • Cationic surfactants have a posi- that a certain product tive charge. Do not use them as is formulated with a Side view of leaf “stand-alone” surfactants—often, wetting agent. If you add they are phytotoxic. another wetting agent when you mix and load • Nonionic surfactants have no a foliar-applied spray, electrical charge. They are often the product may not used with systemic products give better spreading and help sprays penetrate plant and coverage. Instead, cuticles. They are compatible the extra adjuvant may with most pesticide products. increase runoff, reduce A pesticide can behave very dif- deposition, and even ferently in the presence of an anionic, damage the target plant. Without surfactant cationic, or nonionic surfactant. For • Use only those adju- this reason, you must follow label vants manufactured for directions when choosing one of these agricultural or horticul- additives. Selecting the wrong sur- tural uses. Do not use Education Manual factant can reduce efficacy and damage industrial products or treated plants or surfaces. household detergents in Adapted from Penn State Pesticide The terms used when talking about pesticide spray mixes. pesticide additives can be confusing. People sometimes use the words “adju- • Remember that no vant” and “surfactant” interchangeably. adjuvant is a substitute However, an adjuvant is ANY sub- for good application stance added to modify properties of a practices. With surfactant pesticide formulation or finished spray. A surfactant is a specific kind of adju- • Take adjuvant performance Figure 4.1 vant—one that affects the interaction claims “with a grain of salt.” Surfactants increase the of a spray droplet and a treated surface. Be skeptical of claims such ability of the pesticide to All surfactants are adjuvants, but not all as “improves root uptake” or spread evenly over the surface of a leaf or fruit. adjuvants are surfactants. For example, “keeps spray equipment clean” drift control additives and safeners are unless a reliable source can not surfactants. provide research-based evidence to support them. Only use Choosing the Right adjuvant products that have been Adjuvant tested and found effective for your intended use. Here are some factors to con- sider when deciding whether to use an • Test spray mixes with adjuvants adjuvant and how to choose the right on a small area before pro- one for a particular site and situation. ceeding with full-scale use.

PESTICIDE FORMULATIONS 65 SUMMARY

he ingredients of a formulated pes- Most end-use pesticide products Tticide include both active and inert contain adjuvants. Although adjuvants components. The active ingredient con- themselves lack any direct pesticidal trols the pest. Inert ingredients include activity, they are added to pesticide carriers or diluents and adjuvants. The formulations to improve product per- type of formulation may be provided in formance. You should know when and the identifying information on the front how to use an adjuvant. panel of the label. (The SDS for a prod- In summary, you must consider uct will describe the formulation and several factors when choosing a pes- also provide information about hazard- ticide formulation. These include ous inert ingredients.) the risks and benefits associated with Learn what formulations are avail- the options available, the practical- able for the pesticide active ingredients ity of using a specific formulation in you will use. To decide which formulation a particular site to control the target is best for a specific site and situation, you pest, and whether the formulated must know the properties—and be able product will provide effective control. to evaluate the pros and cons—of various Understanding the properties of com- formulation types. You must be familiar mon formulations before choosing a with formulation types and active ingre- pesticide will help you avoid problems dient properties in order to understand and apply your product in an effective the characteristics of the products you use and efficient manner. and apply them properly.

66 CHAPTER 4 Review Questions

CHAPTER 4: Pesticide Formulations

Write the answers to the following questions, and then check your answers with those in Appendix A.

1. The name “X-Pest 5G” on a pesticide label 6. Which dry/solid formulation is mixed in indicates a: water and reduces the risk of inhalation exposure during mixing and loading? A. Granular pesticide with 5% active ingredient. B. Granular pesticide with 5% inert ingredients. A. Soluble powder (SP). C. Gel pesticide with 5% active ingredient. B. Water-dispersible granule (WDG) or dry flowable (DF). 2. Which is the pesticide formulation process by C. Wettable powder (WP). which solid particles are dispersed in a liquid? 7. Which type of dry/solid pesticide formulation A. Emulsion. consists of particles that are the same weight B. Solution. and shape? C. Suspension. A. Bait. 3. Which liquid pesticide formulation consists of B. Granule. a small amount of active ingredient (often 1% C. Pellet. or less per unit volume)? 8. Which is an advantage of microencapsulated A. Microencapsulated (M). materials? B. Ready-to-use (low-concentrate) solution (RTU). A. Delayed or slow release of the active C. Ultra-low volume (ULV). ingredient prolongs their effectiveness. B. Their pesticidal activity is independent 4. Which liquid pesticide formulation may of weather conditions. approach 100% active ingredient? C. They usually require only short restricted- entry intervals. A. Aerosol (A). B. Emulsifiable concentrate (EC). 9. Which type of adjuvant functions as a wetting C. Ultra-low volume (ULV). agent and spreader (i.e., physically altering the surface tension of spray droplets)? 5. Which is a disadvantage of both EC and ULV formulations? A. Buffer. B. Extender. A. Difficult to handle, transport, and store. C. Surfactant. B. Require constant agitation to keep in suspension. 10. Which type of adjuvant increases the viscosity C. Solvents may cause rubber or plastic hoses, of spray mixtures? gaskets, pump parts, and other surfaces to deteriorate. A. Sticker. B. Extender. C. Thickener.

REVIEW QUESTIONS 67 68 CHAPTER 4