White powder on Desert Museum

[Kevin@]

Hello friends,
My Desert Museum has yet another challenge that I can’t figure out. A white powdery mildew is covering its tiny leaves inhibiting growth. It was suggested to me that it might be overwatering so I backed way off and just watered when the ground felt dry (finger test). 1/2 gal every month.
Any help or suggestions would be helpful as I miss those obnoxious yellow blossoms that make my yard a paradise.

 

[DirtMechanic]

4 aspirin in a gallon of water will run it off for 2-3 weeks.

 

[Kevin@]

4 aspirin in a gallon of water will run it off for 2-3 weeks.

Thanks! I applied first treatment. How often do I apply?

 

[DirtMechanic]

It is best to stay ahead of it so a little in every watering works or every 2 weeks.