If you are being asked to interview candidates (especially if you are being asked to coordinate/lead the interviews), then you should also have the time/bandwidth to do the follow-up work with the candidates, even if that means sending them a canned response.

Another comment noted that we're talking about common human decency here--a candidate took time out of their schedule to spend a good chunk of a day (likely more, counting phone screens and travel), and someone can't take a few minutes to even respond to an email. I'm not sure I'd want to work with/under someone like that.