I’ve been wrestling with converting MediaWiki content into Trac and after several experiments, I wanted to start from scratch. It’s not pretty but this cmdline got me there:

trac-admin /svnroot/trac/ wiki list | cut -f1 -d' ' | grep -v Wiki | grep -v Trac | grep -v TitleIndex | xargs -L1 trac-admin /svnroot/trac/ wiki remove