Pesticides emulsifiable concentrates

Mice that were exposed dermally to residues of methyl parathion in emulsifiable concentrate on foliage, and were muzzled to prevent oral intake, developed inhibition of plasma cholinesterase and erythrocyte cholinesterase after two 10-hour exposures (Skinner and Kilgore 1982b). For the organophosphate pesticides tested in this study, cholinergic signs generally were seen in mice with cholinesterase inhibition >50% results for this end point were not broken down by pesticide. 

Atmospheric concentrations of methyl parathion following application of the pesticide to tobacco fields were studied by Jackson and Lewis (1978). They found that levels of methyl parathion decreased rapidly following application of either the emulsifiable concentrate or the microencapsulated form. Air concentrations for the emulsifiable concentrate ranged from 7,408 ng/m immediately following application to 13 ng/m 9 days later. The corresponding measurements for the microencapsulated form were 3,783 and 16 ng/m. ... 

Agricultural (Ag) formulations that are commonly diluted and applied by means of spray equipment include water soluble liquids, emulsifiable concentrates, wettable powders, and flowable suspensions. The choice of which formulation to develop normally depends upon the solubility properties of the technical pesticide. Scientists often must also consider manufacturing costs, field efficacy and product toxicity. 

An emulsifiable concentrate is prepared from pesticides that are soluble in common organic solvents, such as xylene and kerosene. Using emulsifiers in the composition causes the formulation to disperse into small particles, called an emulsion, when diluted in water. 

Fig. 12.11 Examples of pesticide concentration vs. depth, indicating preferential flow of each pesticide in individual field plots. Symbols C continuous I intermittent P ponding S spiinkhng TG technical grade EC emulsifiable concentrate WP wettable powder U undisturbed D disturbed (Ghodrati and Jury 1990)...

Those degradation products which have been identified in our investigations are 1-naphthol from carbaryl, 2,4-D acid and 2,4-dichlorophenol from 2,4-D ester, 2-chloro-2, 6 -diethylacetanilide from alachlor, o,o,oe-trifluro-2-nitro-6-amino-N,N-dipropyl-p-tolu-idine and o,o,o-trifluro-2,6-diamino-N,N-dipropyl-p-toluidine from trifluralin, and a variety of phenols and acids from the degradation of the aromatic solvents used in the formulation of the liquid pesticides as emulsifiable concentrates (41,42). 

Dr. A. Shaw at the University of Maryland Eastern Shore in Princess Anne, Maryland, is evaluating textile substrate for pesticide barrier effectiveness and comfort. Tests will be conducted to assess effectiveness of decontamination processes for these personal protection devices. Diazinon emulsifiable concentrates will be used to contaminate fabrics. Simulated wear studies will be conducted in the laboratory to assess the efficacy of these fabrics in protecting human health. 

Formulation is the form in which the pesticide is delivered to the pest. Some types of triazine formulations are flow-able formulation (FF), emulsifiable concentrate (EC), and water-dispersible granule (WDG). 

Emulsifiable concentrate formulation of diazinon, diluted to field strength (0.5% a.i.) was used to contaminate 100% cotton fabric.7 A single hot-water wash (60°C) results in 1% diazinon remaining on the cotton fabric. When cotton is contaminated with the concentrated (full-strength) diazinon (47.5%), and washed in hot water, 4% pesticide residue remains. 

Emulsifiable concentrate formulation of Triallate, diluted to field strength concentration (1.8% a.i.), was used to contaminate cotton twill fabric. The best laundry procedure is to pretreat the work clothing with a pre-wash commercial soil and stain remover containing a blend of surfactants and solvents, launder in hot water (60°C), and then launder a second time. Approximately 18% of the pesticide remains in the fabric using the above procedure after a single wash when no pretreatment and warm water (50°C) were used, as much as 48% of the Triallate remained. 

Tpo understand the physical and colloidal chemical aspects of pesticidal formulations research, one must first understand the objectives of the formulations chemist in his work. Simply speaking, the formulations chemist must take the pure organic chemical pesticide and put it in a usable form for field use. These forms include wettable powders, emulsifiable concentrates, dusts, granules, water-soluble concentrates, flowables, and an aerosol, to name a few types of concentrates. The formulations chemist desires to put together a formulation that (1) is easy and eco-... 

The emulsion technique was applied in the following manner Microliter quantities of the emulsifiable concentrates of the insecticides were added to distilled water. Portions of each suspension were diluted, and the concentrations of the insecticides in the final suspension were determined by electron capture gas chromatography. Appropriate amounts of the diluted emulsion suspensions were then added to about 1-liter samples of distilled water to provide concentrations of these pesticides at levels of less than one part per billion. 

The major classes of pesticides in use in the Region are organochlo-rine and organophosphorus compounds, Ccirbamates, pyrethroids and bacterial larvicides. Organophosphorus compounds are the most common, followed by pyrethroids. Insecticides are available in a variety of formulations, including emulsifiable concentrates (EC), wet-table powders (WP), dustable powders (DP), suspension concentrates (SC), oil-in-water emulsions (EW) and capsule suspensions (CS). 

The paper by Glatzhofer describes how a computer can be used to operate a viscometer and the paper by Meusberger describes how computer calculations based on solubility parameter theory can be used to optimize the choice of emulsifiers for pesticide emulsi-fiable concentrates. 

Computerized Optimization of Emulsifiers for Pesticide Emulsifiable Concentrates... 

Clearly the above data indicate that microencapsulated pesticides do not necessarily represent a unique hazard to bees, but, to the contrary, there is evidence that this hazard, at least in the case of methyl parathlon, is less than for the emulsifiable concentrate on many crops. 

Solvents are important ingredients of emulsifiable concentrates and of solution formulations. When the formulation is to be used on crops, it is critical that the solvent be nonphytotoxic. The solvent must have a high level of solvent power if an EC is being formulated. Because most toxicants are insoluble in water, the solvent must also be water insoluble. Otherwise, when the EC is added to water in the spray tank, the solvent will mix with the water and leave the toxicant behind as a crystalline precipitate. The carrying power of the solvent, i.e., the amount of pesticide it will hold in solution, is important in the storage stability of formulations. If near its saturation point at ordinary temperatures, it may exceed this at low temperature with the result that solvent and pesticide may separate, causing crystal formation and phase separation (Terriere, 1982). 

The persistence of pesticides in soil is also influenced by their formulations. Granules are generally the most persistent. Wettable powders and dusts are usually less persistent than emulsifiable concentrates (McEwen and Stephenson, 1979). 

The rate of volatilization of microencapsulated pesticides is much slower than that of emulsifiable concentrates (Jackson and Lewis, 1979 Koehler and... 

The pesticide has also been used to control exoparasites on livestock (cattle, sheep, and goats) [20]. Toxaphene is highly toxic to fish. For a short period in the 1960s, it was used as a piscicide to eliminate undesired fish species in lakes prior to the release of commercially attractive fish species. Saleh reported about 817 registered products containing toxaphene in a concentration of 1 % to 80% [3]. Toxaphene was marketed as emulsifiable concentrates, powders, granules, and baits [3]. 

Pyrethroids are formulated as emulsifiable concentrates, wettable powders, granules, and concentrates for ultralow volume application. They may be combined with additional pesticides (sometimes highly toxic) in the technical product or tank mixed with other pesticides at the time of application. AAS-TAR is a combination of flucythrinate and phorate. Phorate is a highly toxic organophosphate. 

Roller pumps are among the least expensive and most widely nsed of all sprayer pumps. They provide moderate volumes (8 to 30 gpm) at low to moderate pressure (10 to 300 psi). Often used on low-pressure sprayers, roller pumps are positive-displacement, self-priming pnmps. The rollers, made of nylon, teflon, or rubber, wear rapidly in wettable powders but are replaceable. A pump that will be subjected to such wear should have a capacity at least 50 percent greater than that needed to supply the nozzles and agitator. This reserve capacity will extend the life of the pump. The pump case is usually cast iron or a nickel alloy. Roller pumps are best for emulsifiable concentrates, soluble powders, and other nonabrasive pesticide formulations (Figure 14B). 

Agricultural Products. Pesticides are frequently applied as emulsifiable concentrates. The active insecticide or herbicide is dissolved in a hydrocarbon solvent which also contains an emulsifier. Hydrocarbon solvent selection is critical for this application. It can seriously impact the efficacy of the formulation. The solvent should have adequate solvency for the pesticide, promote good dispersion when diluted with water, and have a flash point high enough to rniriinii2e flammability hazards. When used in herbicide formulas, low solvent phytotoxicity is important to avoid crop damage. Hydrocarbon solvents used in post-harvest application require special testing to ensure that polycyclic aromatics are absent. 

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