Whether the pesticide is a fungicide, nematicide, insecticide, or herbicide, it is usually available in several different formulations. The choice of formulation is based on:
• the size of the crop area being treated
• the amount of active ingredient being applied
• the other materials being applied along with the pesticide, such as other pesticides or fertilizers
• ease of application
Following is a summary of product formulations and their characteristics.
Solutions The pesticide dissolves into its oil or water carrier as a homogeneous physical mixture. It does not precipitate out, so once dissolved, the pesticide need not be agitated. The pesticide and carrier are in the molecular or ionic state and cannot be separated mechanically.
Emulsifiable concentrates Some pesticides are not soluble in water, yet must be applied in a water carrier. A typical emulsifiable concentrate contains the pesticide, a suitable solvent, an emulsifier, and often a wetting agent, sticker, or antifoaming agent. The concentration of pesticide is usually high, so the cost per pound of active ingredient is rather low. The elements do not settle out, once mixed, so they do not need continuous agitation. Due to their high concentration, they can be dangerous to handle.
Wettable powders These pesticides are of limited solubility in water. They are combined with dilating agents and surfactants that prevent flocculation of the pesticide particles. Wettable powders require continuous agitation to ensure uniform coverage. They are relatively low in cost, easily stored and handled, but are hazardous if inhaled or absorbed through the skin.
Granules and pellets These pesticides are formulated as coarse, solid particles for easy application. The carrier may be sand, clay, ground corn cobs, fertilizer granules, or vermiculite. No dilution is required since the percentage of active ingredients is lower than in other formulations, usually between 4 and 10 percent.
Fumigants These pesticides come in the form of poisonous gases that kill when absorbed or inhaled. They are most useful in greenhouses or other enclosed areas where they penetrate into cracks and crevices and into the soil. They are often highly toxic.
Dusts These are fine powders containing the active ingredient in low concentrations and mixed with a high percentage of inert carrier material. Applied dry and directly to the plants, dusts leave a visible residue.
Flowable suspensions These are wettable powders, not soluble, that are suspended in a water-based carrier material. It is usually necessary to agitate the product during application to ensure a uniform coverage.
Gels A gelatinous form of the pesticide, gels are commonly used as the formulation inside containers that are to be returned for recycling. This is also the formulation common in water-soluble packets.
Water-dispersible granules These are granular formulations that are applied in water. They have a low solubility in water, so continuous agitation is required during application to ensure even distribution.
Water-soluble packets Containing pre-measured quantities of gels, powders, or granules, the packets dissolve in water and once mixed require no further agitation during application.
Soaps These are actually oils produced from plants. They are applied as sprays by growers and in mist bottles by home gardeners.