If the bulb is presented without any watering, please do not remove the bulbs from the arrangement; this will disturb the root growth. On occasion, mold may form on the bottom of the bulb. This natural event is harmless and the mold will disappear as soon as the plant is put in dry storage after it's done flowering.
If the display contains water, then we suggest you carefully take out the bulb, and rinse the mold off the bulb. Take care not to damage the roots while doing so. Remove any moss if it comes with the display, as mold can accumulate on that too.