Help ID rhododendron leaf problems

Can anyone help me assess may be wrong with my friend's rhododendron. It is looking a little stressed and I have attached pictures of the affected leaves. I can't tell if it might be powdery mildew or sun scald or lack of water, or what.

Thank you.

Susie

 

Looks like sun damage to me, probably got baked last summer.

 

Here in Vancouver sun scald is more likely to happen on bright sunny winter days when the ground is frozen solid and the plants can't replace the water evaporated by their sun-warmed leaves. I spray mine each fall with Wilt-pruf, a natural oil emulsion which reduces transpiration. It has been great for keeping my Rhodos unburned and doesn't seem to cause any problems. It's also good for reducing summer transplant shock in shrubs.

 

Heat or cold-induced desiccation: Antitranspirants had no effect

http://www.puyallup.wsu.edu/~linda ...ltural Myths_files/Myths/Antitranspirants.pdf