Using feedback to reduce plagiarism
Feedback, particularly on formative drafts of pieces of work, can play a huge role in reducing plagiarism. This is for two reasons. The first is that by asking your students to produce a draft, before the final piece of work, you can see how their ideas start to form, and then are shaped by that feedback. This ideas-development is difficult to copy-and-paste and so the students are more likely to do their own work. You could even ask them to comment on how they changed their work in response to your feedback when they hand in their final piece of work. This requires your students then, not only to read the feedback but discuss how they acted upon it.
The second reason is that the support given by the feedback should encourage the student to improve their work and this in turn can, for some students, be enough to encourage them away from plagiarism. It does, however, really highlight the need for the feedback to be positive and constructive.