3 of my mexican hats are being attacked by some kind of white powdery fungus with tiny black dots. It looks like someone poured milk and gun powder on the foliage. A few of the leaves are dead but new growth is coming out up top so I'm not sure its deadly. Still the plants do seem in stress. These plants are in more shade then the healthy ones. Possible the rain and lack of stress has caused a mold or fungus to grow?
I have only fertilized with organic low Nitrogen goods so I don't think its caused by that. All my other plants seem to be oblivious to this bug. The salvias, agastaches, and penstemons have not noticed at all.
Help needed with mold or fungus
With Mexican hats since they are so strong, I would just cut them back rather than fight the fungus.
They grow back quick, and you would eliminate the chance of the fungus spreading. Otherwise try low fat milk and water 1to 10 ratio and spray them with that.
Josephine.