Azalea leaf disease
I have foundation plantings of azalea at front door. Experienced some leaf yellowing during late summer and used a fungal spray which was somewhat effective tho applied late in season. At beginning of Dec noticed significant yellowing and leaf shedding. Can I do anything to help at this time? Should I rake and destroy yellow leaves on ground under plants? Thank you!!
Do you have any photos of the yellowing that you saw?
The only reason you'd possibly use a fungicide is if you had an azalea rust disease, which is a problem only for deciduous azaleas and is not very common.
(Spraying of any pesticide on a day with temps above 85 degrees can cause leaf damage).
Some leaf yellowing and drop is normal late in the season and during the winter.
Probably the most common problem that azaleas have, especially if they are grown in full sun, (and more likely if you use pesticides, which kills the beneficial insects that often keep them in check) is lace bugs. These suck on the leaves, leaving stippling spots- yellowish to later whitish/silvery results. If you flip leaves over, you would see black fecal spots on the underside.
Here is our publication which discusses problems of azaleas: https://extension.umd.edu/learn/ipm-series-azaleas-and-rhododendrons-hg51
Raking fallen leaves will is o.k.