The composition comprises an aqueous solution containing (1) a water insoluble compound selected from zinc arsenate, zinc arsenite, copper arsenate and copper arsenite, or a mixture thereof (0.1-4% by weight); (2) a water-repellent component (0.15-10%) consisting of either a phosphoric acid ester of a monohydric alcohol or a mixture of the acid ester and a zinc or copper carbonate; and (3) ammonia (1. 28%) sufficient to solubilize the first two components. -- AATA