Rhododendrons: Rhodo leaf "dieback"(?)

I live upon an eastern exposure in the Upper Sunshine Coast, and have planted many rhodos since moving here fic\ve years ago. Late this fall, one of my smaller rhodos began showing the odd bare branch, which I at first attributed to our pesky deer (which usuaully ignore rhodos!). But the problem is growing and spreading, particularly among my three r. hallelujahs, one of which has now lost over half its leaves.

A crack first appears at the leaf's stem, which eventualy breaks and allows the leaf to hang until -- eventually -- it blows off in a wind. I planted these rhodos over three years ago, and they were in glorious helth until now. Upon inspection, this morning however, the problem seems to have spread to a much larger r. rainbow, which is on another side of the house completely. This plant is at least ten years old, and also seems to be in fine shape otherwise.

Can anyone direct me or help me diagnose my situation? I have photos and/or additional info if this would help.

Sincerely,

Richard John Aylmer

 

Rhododendrons are prone to dieback diseases and leaf diseases. Start with doing web searches with phrases like "rhododendron diseases" and you will find there is quite a bit online. However, exact determination might end up requiring sending samples to a lab. Down here Cooperative Extension could assist with this. Analag up there would probably be Ag BC/BC Ag (whichever it is) - don't know what similar services they might offer.