Polymeric microcapsules of alachlor and metolachlor: Preparation and evaluation of controlled-release properties

The microencapsulation of alachlor and metolachlor in the polymers cellulos e acetate butyrate, ethyl cellulose, poly(methyl methacrylate), and poly(al pha-methylstyrene) with different emulsifiers is described. The controlled- release properties of these formulations were measured under greenhouse con ditions on barnyardgrass, crowfootgrass, smallflower morningglory, and Palm er amaranth. The emulsifiers had little effect on the activity of the herbi cides. The herbicidal activities of the poly(methyl methacrylate) and poly( alpha-methylstyrene) formulations were consistently lower on all weed speci es when compared to the activities of the cellulose acetate butyrate, ethyl cellulose, and commercial formulations. The ethyl cellulose formulation of alachlor exhibited controlled-release properties. The results with metolac hlor were similar to those with alachlor except that none of the metolachlo r formulations exhibited efficacy superior to that of the commercial formul ation or controlled release properties.