Since most microform materials found in the Library are simply photographic, miniature reproductions of what had once been a full-size newspaper, book, or magazine, actually citing the format of the publication should be avoided.
The rare exception to this rule is when the nature of the publication is essential information. The fact that you used the microform version of the Journal of Applied Psychology would be important in, say, a study comparing usage of microfilm and paper sources in research. Another instance when the format is important is when the publication is only available in a microformat, such as a letter included in a collection of personal papers, or an ERIC document, to name two examples.