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

The microencapsulation of alachlor and metolachlor in the polymers cellulose acetate butyrate, ethyl cellulose, poly(methyl methacrylate), and poly(alpha-methylstyrene) with different emulsifiers is described. The controlled-release properties of these formulations were measured under greenhouse conditions on barnyardgrass, crowfootgrass, smallflower morningglory, and Palmer amaranth. The emulsifiers had little effect on the activity of the herbicides. The herbicidal activities of the poly(methyl methacrylate) and poly(alpha-methylstyrene) formulations were consistently lower on all weed species 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 metolachlor were similar to those with alachlor except that none of the metolachlor formulations exhibited efficacy superior to that of the commercial formulation or controlled release properties.