Q.Can you identify this diease or pest & what is cure?
Rhododendrons leave are covered in black sooty deposits, and the underside of leaf has white strips mainly down the spine of the leaf. The actual Rhodies are 50+ years old.

theficuswrangler
Answered on June 29, 2014
This article should provide you with some answers: https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron/rhododendron-sooty-mold.htm
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