I have three mature rhododendrons (planted in 1985) in the front of my home which have always been very hearty and healthy until last year. I have attached a photo of it in which you can see one of the others. I am afraid that I might be too late to rescue it, but would like to know what has happened so I can try to prevent it from happening with the remaining plants and whether it will be safe to plant anything in the same spot. Thank you for your assistance.
Yikes! I'd suggest you bring in a plant sample for evaluation. Here is link to the appropriate form you'll complete and submit with your sample, as well as tips and hints for taking the sample so we can best evaluate http://extension.udel.edu/ag/plant-diseases/ud-plant-diagnostic-clinic/. Once you've organized everything you need, you can bring the sample and form to the NCC Extension office, 461 Wyoming Road, Newark, Delaware. Additional questions/concerns contact the garden line (302) 831-8862.