Significance

• Any time a plant's foliage becomes disfigured or discolored, it is cause for concern. There can be any number of pests and diseases that cause this condition and prompt diagnoses and treatment is vital.
  
  

Causes

• Rhododendrons are notoriously susceptible to chlorosis. This is not a disease, per se, but an iron deficiency that causes new leaves to grow in yellow.
  
  

Solution

• Treat both the foliage and the soil with a chelated iron fertilizer, according to the package instructions. You should also test the soil pH and adjust it with iron sulfate to 4.5 to 5.5. Finally when you fertilizer, use a fertilizer labeled for use on acid-loving plants.