The Chicago Manual of Style advises that you need to include the following components in a reference to a lecture of presentation:

• Name of the Presenter(s) (In the footnote given as First Name Surname, in the Bibliography given as Surname, First Name)
• "Title of the lecture / presentation"
• Type of source (Lecture etc.)
• Institution or Organisation or Society hosting the lecture / presentation
• Place
• Date of the lecture / presentation

In a footnote everything which follows the title of the lecture is given in parenthesis.

Footnote / Endnote Format:

First Name and Surname of Presenter, "Title of the Lecture / Presentation". (Lecture, Institution, Place, Month DD, YYYY)

Bibliography Entry:

Surname, First Name of Presenter. "Title of the Lecture / Presentation". Lecture, Institution, Place, Month DD, YYYY.

Where a lecture is subsequently published in a book, reference as a chapter in a book; where a lecture is subsequently published in a journal, reference as a journal article.