The present invention relates to benzenesulfonamide derivatives of the formula I in which the variables are as defined below: X1 is hydrogen or halogen; X2 is hydrogen, cyano, CS—NH2, halogen, alkyl or haloalkyl; X3 is hydrogen, cyano, alkyl, alkoxyalkyl, cycloalkyl, alkenyl, alkynyl or phenylalkyl, where the phenyl radical for its part may be substituted; Y is a group —C(A)B, SO2 or SO2NR2; A is oxygen or sulfur; B is oxygen, sulfur, NR2 or a bond; R1 is hydrogen, halogen, hydroxy, alkyl, cycloalkyl, cycloalkylalkyl, alkenyl, cycloalkenyl, alkynyl, alkoxy, cycloalkyloxy, alkenyloxy, alkynyloxy, aryl, aryloxy, arylalkyl, where the 13 last mentioned radicals for their part may be substituted; unsubstituted or substituted four- to six-membered heterocyclyl; unsubstituted or substituted four- to six-membered heterocyclyl-C1-C4-alkyl; unsubstituted or substituted five- or six-membered heteroaryl having one to four nitrogen atoms or having one to three nitrogen atoms and one oxygen or one sulfur atom or having one oxygen or sulfur atom; or unsubstituted or substituted five- or six-membered heteroaryl-C1-C4-alkyl having one to four nitrogen atoms or having one to three nitrogen atoms and one oxygen or one sulfur atom or having one oxygen or sulfur atom; R2 is hydrogen,-alkyl, alkenyl, alkynyl, cycloalkyl, where the four last mentioned radicals may be partially or fully halogenated; or R1 and R2 together with the nitrogen atom to which they are attached form an unsubstituted or substituted three- to seven-membered heterocycle; Q is a radical from the group consisting of Q1 to Q39; to processes and intermediates for their preparation and to the use of these compounds or of the compositions comprising these compounds for controlling unwanted plants and for the desiccation/defoliation of plants.