Recently developed zirconium based fungicides, obtained through the solubilization of metal salts with zirconyl acetate and zirconyl ammonium carbonate to form derivatives which revert to insoluble effective residuals on heat curing, have demonstrated improved fungicidal resistance through metal ion combinations. Derivatives of silver and copper with zirconium show a much greater protection for cotton than the protection afforded by either of the metal ions in separate treatments with the same metal content. This is effectively demonstrated through soil burial evaluations in which the combined silver and copper derivatives were buried with the separate treatments in varying concentrations and with an untreated control. The results demonstrate a definite additive effect.