Brown and spotted leaves on Rhododendron
I have an established Rhododendron that is showing brown, dried, drooping leaves with black spots this Spring. Most of the plant is OK -- the diseased leaves appear on the ends of some branches, but not others.
It is planted in a little-bit acidic soil (near to a Hemlock tree), part shade (some afternoon Sun), appears well-drained, and is not regularly watered (well-established at least 10 years, I am guessing).
A neighbor's Rhododendron (located 50 feet away) is much more heavily impacted by what appears to be a similar affliction.
I've looked through some pages here and elsewhere (Penn State) but am unable to make a definitive diagnosis.
Any ideas what is wrong with these Rhododendrons?