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.