When to prune a Flower Spike
 

I have a Miltoniopsis and a Zygopetalum plant. Each have multiple flower spikes with flowers in bloom and each have a flower spike with spent blooms. When should the spike be pruned and where should it be pruned? I've searched culture sheets but to no avail.

I wait until they turn brown,then prune carefully as close to the main plant as possible making sure your that what yu use to prune is "sterilized" and dab the pruned end with cinammon.

I agree, cut closely at the base of the spike. Apply cinnamon. Only Phalaenopsis can be pruned halfway and re-bloom on the same spike.