Use of esterquats as microbicidal agents

The invention relates to the use of quaternary ammonium esters selected from the group formed by (a) quaternary ammonium esters of formula (I), where R CO = an acyl group with 16 to 30 carbon atoms, R and R independently = H, or R CO, R = 1 - 4 C alkyl, or a (CH2CH2O)qH group, m, n and p = in total 0 - 12, q =1 to 12 and X = halide, alkyl sulphate, or alkyl phosphate, (b) quaternary ammonium esters of formula (II), where R CO = an acyl group with 16 to 30 carbon atoms, R = H, or R CO, R and R independently =1 - 4 C alkyl, m and n = in total 0 - 12 and X = halide, alkyl sulphate or alkyl phosphate and (c) quaternary ammonium esters of formula (III), where R CO = an acyl group with 16 to 30 carbon atoms, R = H, or R CO, R , R and R independently = 1 - 4 C alkyl, m and n = in total 0 - 12 and X = halide, alkyl sulphate, or alkyl phosphate, as microbicidal agents.