The invention relates to novel 2-alkoxy-6-alkylphenyl-substituted spirocyclic tetramic acid derivatives of the formula (I) ##STR00001## in which A, B, D, G, X, Y and Z are as defined above, to a plurality of processes and intermediates for their preparation and to their use as pesticides and/or herbicides, and also to selective herbicidal compositions comprising, firstly, the 2-alkoxy-6-alkylphenyl-substituted spirocyclic tetramic acid derivatives of the formula (I) and, secondly, at least one crop plant tolerance promoter compound.