Does a les pendes need to be filed when a slander of title action is filed

It's "lis pendens". You would only file it if you believe the other party would or might, unless you did file it, possibly transfer what interest that other party has to an innocent "good faith" ("bona fide") purchaser.

This is strange. I see only my answer which I wrote in January of last year. So why is this thread near the top of the forum?

And by the way, although OP never responded, I should modify my answer. If OP is filing an action against someone for slander of title, the property presumably belongs to OP. So I can imagine no reason why OP would need to file a lis pendens against his/her own property.

It's at the top because someone piggybacked on it last night and I just moved it to its own thread.