Parasect is interesting as well because it knows a move that can induce paralysis, which remains on the opposing pokemon (while pokemon with sleep status can lose it after 2-5 turns)
And what @xPredators says is true as well, false swipe sounds risky if wild Beldum knows a self-damage move. I assume the attack is normal (which Ghost pokemon resist, so in other words it cancels the move and avoids beldum take any self-damage)
Best is to damage it is as low as possible, but not so low that it would knock itself out. Switch to a ghost pokemon (ghastly as an example) and then keep throwing and hope for the best.