cotton plants may be rendered male sterile while retaining substantial female fertility by contracting the plants with a gametocidally effective amount of a novel compound which has the formula : ## str1 ## where x is oxygen , sulfur , or ## str2 ## and where r is a substituted and unsubstituted aryl , alkyl , cycloalkyl , alkoxy and alkene group , and maintaining the effective amount for a sufficient time to form sterile plant flowers that can then be pollinated by a second variety cotton plant to provide cotton having hybrid cotton seeds .