Yes, PRUNERS is a Scrabble word!

Letter values in Scrabble US: P 3, R 1, U 1, N 1, E 1, R 1, S 1.

Is it a valid word?

PRUNERS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a worker who thins out and trims trees and shrubs
a long-handled pruning saw with a curved blade at the end and sometimes a clipper; used to prune small trees

Also: pruning hook.