Allophanates of the formula: ##EQU1## wherein: THE X's are oxygen or sulfur; R.sub.1 is hydrogen, certain organic radicals, or halogen; and R.sub.2 and R.sub.3 are certain organic radicals, Are useful for the control of flowering and plant sexual reproduction. A preferred use of the compounds of the present invention is to prevent corn inbreeding by applying the allophanate to the plant at or shortly before tassel emergence. Exempliary of such compounds is: ethyl 4-[1-(4-chlorophenylcarbamoylimino)-1-(methoxy-methyl)]allophanate.