There is disclosed an improved copper complex bactericide/fungicide and a method of making and using the same. The improved bactericide/fungicide is prepared by forming an aqueous solution of a partially neutralized, water-soluble polycarboxylic acid having a molecular weight of between approximately 1,000 and 300,000 and a pH of between approximately 3 and 9. To this aqueous solution is added a copper-containing compound which when combined with said aqueous solution releases copper (II) ions which will form a water-soluble complex with said partially neutralized polycarboxylic acid. The water-soluble copper complex is applied to plants to prevent or inhibit bacterial and fungal disease growth thereon.