Hi -- Seeking opinions on what to do, if anything, about brown spots and discoloration on Rhododendron leaves. I found info about brown spots with white in the middle but there is no white spots on these leaves. Well-establishes plants in Zone 6, NJ
My best guess is a fugal leaf spot called Cercospora. Generally only an aesthetic issue. Make sure to =remove fallen leaves to partly interrupt the transmission cycle. There fungicides that can be used, but these only effective if used as a preventative, and thus must be used every year, The disease is gen worst when humidity is high in the spring, and when temps. hover near 50 deg F during these humid times.
Good luck
Thanks for reply. Looks similiar if not the same.
OK, I know that Rhodo also gets Septoria. Maybe a better candidate.
Did you have a wet spring last year? It's last years damage. Fungal leaf spot of some sort. Not cured only prevented. In a wet spring you would be spraying fungicides until the cows came home.
1) Wind and cold damage is indicated when the edges of the leaves become distorted and turn brown. This occurs frequently in plants that may be in a colder climate than recommended or in a location with severe exposure. Note, boron poisoning will create the same symptoms. 2) Large leaved rhododendron are susceptible to sunscald if the plants do not receive enough moisture before the soil freezes. The leaves curl in cold winter weather, exposing the central part of the leaf but not the edges, resulting in the area near the main vein becomes desiccated and turns brown. To prevent this, water plants thoroughly before the first hard frost, protect from drying winds, apply mulch, and locate in partial shade. 3) If a leaf has brown areas with white spots, it probably has a local fungal infection of Pestalotia leaf spot. This is seldom controlled with fungicides and is best mitigated by good sanitation and avoiding excessive moisture.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.