Pesticides formulations: Invert Emulsions
A pesticide formulation is a combination of active and inert ingredients that forms an end-use pesticide product. Pesticides are formulated to make them safer or easier to use. This is because many pesticide active ingredients, in “pure” (technical grade) form, are not suitable for application. In their concentrated form, some are extremely toxic, many do not mix well with water, some are unstable, and some are difficult (or unsafe) to handle, transport, or store. To address these problems, manufacturers add inert ingredients to end-use pesticide products. Inert ingredients have no pesticidal activity, and some simply serve as diluents or carriers.
Invert emulsions contain a water-soluble pesticide dispersed in an oil carrier. These products require a special kind of emulsifier that allows the pesticide to be mixed with a large volume of petroleum-based carrier, usually fuel oil. Invert emulsions are less susceptible to drift because oil evaporates more slowly than water. When applied on a hot, dry day, a water-based droplet will become smaller as the water portion of the droplet evaporates. Invert emulsion droplets do not “shrink” as rapidly when applied in the same weather conditions. This means less drift and more pesticide on target. Invert emulsions are thick mixtures, with the consistency of mayonnaise. In addition, invert emulsions are applied as very large droplets, which reduce drift.
The oil phase of this kind of formulation also serves as a sticker spreader This quality improves rainfast properties and surface coverage. It also increases absorption and/or penetration. This, in turn, reduces loss due to runoff. Invert emulsions are relatively uncommon. They are most often used in weed control on rights-of-way to reduce the chance of drift to susceptible non-target plants or sensitive areas.
- Low drift.
- Increased rate of penetration and/or absorption.
- Increased rainfastness and reduced runoff.
- Difficult to treat the underside of foliage or other targets because droplets are large and heavy.
- Limited availability.