26+ Rhododendron Leaves Turning Brown. Why the sudden appearance of damaged leaves? Symptoms are pale spots on upper leaf surface, with corresponding brown/grey patches underneath:
This article reviews the most common problems and how to so, allow time between each watering for the soil to dry out slightly and for the roots to regenerate.
Rhododendron borer causes wilting of leaves and twig dieback. I've researched but can't work out whether its too much or too little water. Brown, yellow or wilted leaves? Prune off the suspected branches and split them open longitudinally to see if larvae are present.