The mums I planted last fall were looking great until last week, when almost over night, big sections of the bushes began dying back. We did get three thunderstorms last week, which dropped a total of 3 inches of rain. But they're survived similar rainy spells earlier in the season. Why now? Also, I've sprayed them with fungicides every other week when I spray the roses.

I know they're shallow rooted and like well drained soil & full sun, so I planted them high and in raised beds.

Second thought...remove several of the thickest stems, split them open lengthwise and check to see if there are any tiny 'ants' living inside the stems. This is a new problem we here in the south need to be alerted to. Reports are trickling in that plants are suddenly wilting due to Formosan termite living inside the stems. Doubtful that this is your problem but they are in the Charleston and south areas.

Next process would be to pull up a plant and check the roots for signs of root-knot nematodes. Another possibility. And, it could just be a weather related problem. We have had lots of rain followed by blistering heat which may affect mum growth.