bird of paradise disease?

Question

The flower shows black blotches all over but only starts to appear as the flower opens. A dissected flower shows no sign of disease prior to opening.

Answer 1

This likely is a fungus issue.
Treat the plant with Neem Oil and do so weekly as a preventative weekly through the growing season.

https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
https://www.gardeningknowhow.com/ornamental/flowers/bop/bird-of-paradise-an-exotic-flower-like-none-other.htm