Excessive foaming can be a significant problem with some agitation systems in sprayers and especially when the water level in a tank gets down so that a mechanical agitation system would be causing excessive foam. Since aerial applications normally are made with highly concentrated spray mixtures spray nozzles that create small droplets are often used. Extenders are adjuvants that can extend the useful life of a spray chemical. This can be accomplished by increasing the adhesion of the chemical to the leaf or by reducing any factor that can diminish chemical effectiveness or by enhancing the weatherability of the chemical. Since many pesticides are broken down by ultraviolet light some extenders have the ability to intercept UV light.
Spreaders are surfactants.
They stick and spread chemicals to plant surfaces. See stickers for that description and see surfactants for the spreader part of these compounds. Stickers are adjuvants that aid the attachment of a chemical to a surface and can lengthen the time that a chemical will be attached to a plant surface. Stickers generally make pesticide deposits less easily removed from leaves by forces such as rain or wind. They stick and spread chemicals to plant surfaces.