Question
have a bed of Gin dark leaf begonias, found two this morning with very deformed thick white spore looking growth over the entire crown of plant, need to spray immediately since this is a wedding landscape job for this weekend, what would be the best to spray to keep this from spreading to the rest of the bed?

Answer
AmyDaniel,
The way you describe it makes it sound more like a slime mold to me than a fungus. Why don't you just remove what you see by hand, and wait a couple of days to see if anything is spreading?  Is this bed being watered frequently? Does it have bark mulch on the soil? If the answer to both of those is yes, it's likely to be a slime mold and these are pretty harmless. You can take most of it away with a trowel. Fungicides don't work on slime molds anyway, so you'd be wasting your time with spray.

Also, even fungal conditions are made worse by frequent watering. Usually, however, fungus just makes the stems turn black and the plant die, but you don't see anything resembling a "deformed thick white spore looking growth."

Water deeply but less often instead of a little every day or every other day.  Hand remove what you can see. Most slime molds disappear  in a matter of 4 or 5 days.

all the best,
C.L.