Answer: Fungal diseases are quite common on rhododendrons grown in the Pacific Northwest. What you describe sounds like a fungal disease. To manage, avoid overhead watering, avoid wounding plants, as wounds provide ideal infection sites. Be sure to rake and destroy fallen leaves to prevent the spread of infection. Remove infected leaves from your plant. Prune infected branches back into healthy wood. Destroy, do not compost, diseased plant material. Rhodies do appreciate an acidic soil. You can topdress with peatmoss which will help acidify the soil, and you can feed with an acidified fertilizer (such as Miracle Gro).
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