"Equally good activity showed the compounds of the formula Id ##STR6## wherein n is zero, 1 or 2, R1 is C1 -C3 alkyl, R2 is fluorine, R3 is chlorine or bromine, A is a C1 -C4 alkylene bridge and the R11 are independently of each other C1 -C4 alkyl or C1 -C4 alkoxy, especially N-[4-chloro-2-fluoro-5-(triethoxysilylethylthiocarbonyl)phenyl]-3,4,5,6-tetrahydrophthalimide." . . . .