I have had thriving stands of Shasta Daisies for years, and have divided and planted them elsewhere, and they thrived there as well. Last year, they began to die out. After blooming, the stalk and roots died. Some other daisies are also affected. What is going on and what can I do to keep all of the daisies from dying?
Shasta Daisy Disease
Certified GKH Gardening Expert
The symptoms you describe could be caused by watering problem, either overwatering or underwatering. But since you have grown daisies for years and never had this problem before, and since multiple types of daisies are affected, this seems more likely to be a disease.
Look over this list of daisy diseases from the University of California:
It looks like Acremonium wilt or Cottony rot may fit your plants' symptoms. In this case you may not be able to grow daisies in that same spot for several years.
Since different diseases are present in different regions, you should check with a local university extension agent or do some research on daisy diseases present in your area.