Abstract: Acetolactate synthase inhibitors, such as imazapyr and pyrithiobac and mixtures thereof, prepared as slow-release formulations are useful for the preparation of seed dressing, seed priming, seed or particle-substrate coating herbicidal compositions for control of parasitic weeds such as Orobanche spp., Striga spp. and Alectra spp. The use of agrochemicals can be rendered more efficient when coated or bound as a slow release formulation. Particles used as the substrateto be coated may be plant seeds or particles made of a strong or weak ionic resin or a biodegradable carbohydrate natural polymer, a modified polymer, or artificially lignified cellulose. The herbicidal formulation may be covalently linked or adsorbed to the surface of the particle. The same slow release formulations are invaluable for preventing rapid herbicide leaching in agricultural as well as non-agricultural weed control situations.