The flower buds fail to open and turn black or brown. Numerous tiny black bristle like threads cover the bud.

The fungus is spread by leaf hoppers as they lay their eggs within the bud scales. The fungus spreads within the bud, eventually killing it. The bristle like threads are the spore producing fruiting bodies of the fungus. The spores are picked up by the leaf hoppers.

Generally impractical. Leaf hoppers could be controlled by insecticide but plants would become quickly infested again from neighbouring plants.

Pinch out infected buds immediately.