My ligustrum lucidum hedge is about 2 years old and has suddenly had leaves turning yellow with brown crusty spots on them. How do I kill this desease and what is it?
This sounds very much like cerospora fungus. It can be due to damp weather or excess moisture levels. If your hedge is not receiving good sunlight also can cause issues.
Prune out the diseased material and dispose of, rake the ground and clean up the litter.
Treat the plant with a fungicide like myclobutanil or Immunox.