Functionalized polymers are mixed with pesticides to form semi-stable complexes with desirable field properties: reduced leaching in soil, improved leaf retention (rainfastness), selective unloading to roots and convenient packaging and application. Pesticides that may be so complexed include herbicides, insecticides (including compounds controlling non-insect arthropods and nematodes), bacteriocides, rodenticides, and fungicides. Polymers with which they may be complexed include derivatives of carbohydrates, amides, imines, alkanes, vinyls, styrenes or glycols. The polymers may be functionalized with chemical groups that exhibit ionic (amines, carboxyls), hydrophobic, complexing (e.g. metal chelating) and ligand binding interactions. The variously functionalized polymers may be mixed, grafted, or fused to obtain optimal properties. The polymer/pesticide formulations may be applied as granules, as suspensions or solutions in sprays, as foams, or as coats for seeds and fertilizers. The formulations may be applied to foliage, soil, irrigation water, construction materials (plastics, wood), seeding materials, grains, and buildings.