How do I deal with fungus on my gerberia daisy?

I got this gerberia for Secretary's day and it's been sitting on my desk. Otherwise, it seems perfectly healthy. I just cut off the blooms it came with and some baby flowers are shooting up. About a week ago it started showing white powdery stuff on its leaves and it seems to be spreading. Where the powder is thickest, the leaves are also turning black. What should I do?How do I deal with fungus on my gerberia daisy?
';Powdery mildew is common on woody plants including roses, crape myrtles, euonymus, dogwood and oak, as well as herbaceous plants such as verbena, phlox, monarda, and gerbera daisy.';


';Reduce humidity by increasing air circulation.


...


Remove affected stems or leaves from the plant to reduce disease pressure.';





There are also fungicides you can use safely, but I would recommend the above firstly.