The invention relates to treatment of yarns for use in reinforcement of rubber products. Such treatment comprises application to the yarn of an aqueous emulsion of polyester and/or epoxy adhesive, or an aqueous alkaline dispersion of rubber latex and resorcinol-formaldehyde resin adhesive, wherein said adhesive contains a minor amount of particulate, water insoluble starch composite of starch and water insoluble plasticizer therefor. Such yarns may be in a form of a cord comprised of a plurality of yarns. The invention further relates to such treated yarns. The invention additionally relates to such treated yarns and a composite of rubber and said treated yarns. The invention additionally relates to an article of manufacture such, as for example, a rubber tire, having at least one component comprised of said composite.