How do I delete a discussion in a course?
You can delete a discussion or graded discussion at any time.
Note: When Multiple Grading Periods are enabled in a course, graded discussions are not currently validated against closed grading periods. Deleting a graded discussion may affect the total grade for students in your course.
In Course Navigation, click the Discussions link. There are two ways to delete a discussion topic.
To delete a discussion from the index page, locate the discussion. Click the Options icon  and click the Delete link .
To delete a discussion individually, click the title of the discussion.
To delete a discussion in the Discussions Redesign interface, click the Options icon  and click the Delete option .