How to disable blog avatar in Avatars plugin?

On my site, one user can only create one blog, so that I wanna disable blog avatar from Avatars plugin, just remain the user avatar, how do I do it? removing the "blog avatar" link from the admin menu seems to be the easiest way, but it does not really disable the blog avatar.

another workaround I am thinking, is to upload a same avatar to blog avatar as well when uploading user avatar, is there a handy way to realize this?