Something has upset the bay tree - and it is not happy. It could be:

• too much water. We have had a wet year. Is the drainage good under the tree, so that the water can get away?

• nutrition - Is the tree in reasonably fertile soil? It may need some plant food or it could be suffering from a lack of iron in the soil. It is possible to buy iron fertiliser.

• climate - is it in a cold, windy position? If so, try to provide shelter.

• insects - Bay sucker (Trioza alacris) spoils the bay leaves. Bay tree leaves thicken and curl at the margins and turn yellow. The discoloured areas later dry up and become brown.
  

The infected leaves should be picked off & got rid of & badly affected shoots can be pruned out.

Click this link to see herb growing cards