Imac doesn't recognize Sandisk ultra micro SD card or card reader

I have a new 64 gb Sandisk ultra micro SD card and an older imac running OS X 10.5.8. When I plug the card into the card reader and then into the imac, the computer doesn't recognize the card and does not see the reader. The same reader works with CF cards on the same computer. The same card and reader work on a 6-month-old macbook air. Should I assume my imac is too old to read micro sd cards?