Sunlight is the most natural and effective mold killer on any surface. If your cinder block wall lacks sunlight because of an overgrowth of plants, stacks of boxes or gardening tools, remove all of the barriers to ensure ample sunlight exposure. If your wall simply doesn't get much sunlight, use a more proactive removal method.
The Environmental Protection Agency recommends the use of a wet-dry vacuum for removing moisture from a cinder block wall. Using the "Suction" setting, you can remove moisture from deep within the cracks and pores of each cinder block. Without moisture, mold dies instantly, as it cannot germinate in a dry environment.
A HEPA vacuum functions less like a wet vacuum and more like a conventional vacuum, but with one exception. It is specifically designed to filter bacteria and impurities. Like the wet vacuum, the EPA recommends the HEPA vacuum as an effective means of eliminating mold from cinder blocks. Use a hose extension to vacuum all areas affected by mold.
The acetic acid in white vinegar is useful for killing mold on contact. Since the acid is mild, it will not damage your cinder block wall. Before spraying full-strength vinegar on your cinder block wall, dampen the wall with water. This will prevent the vinegar from being drawn into the crevices. After spraying the vinegar on your cinder block wall, wait about 15 minutes and rinse with water.