The invention relates to synergistically active mixtures for the control of phytopathogenic fungi and bacteria comprising antimicrobially effective derivatives of a phenol of the general formula ##STR1## R.sub.1, R.sub.2, R.sub.5 and R.sub.6 represent hydrogen (for R.sub.5 and R.sub.6 only), bromine, chlorine or alkyl with up to 5 C-atoms, R.sub.3 represents hydrogen, sodium, potassium, calcium, barium or ammonium*, magnesium, bismuth, tin, zinc or copper, furthermore R.sub.1, R.sub.2 and R.sub....