Depending on its size, its symptoms, how long it's been planted, and where it is planted.... for example, if it's a young bush/tree which you have just put in the soil, you could dig it up and replant it in good compost in a large pot, as it's probably the soil conditions. If it's a well established bush then it could be seriously diseased.
Can you describe some of the above and people will be more able to give you good advice?