Answer: Unfortunately, based on your description, it may be too late. Usually it is best to troubleshoot this type of problem as soon as you notice it starting. That way you have a better chance of stopping its progression before it does significant damage to the plant.
Working with the information in your question, I am not able to give you an identification of the plant or the problem (for example, it might be mites on a spruce or possibly a disease problem if it is a juniper, or it might be due to underwatering or overwatering or poor rooting or overfertilizing or any number of possibilities), so I can't make any suggestions as to what to do. But in case it can still be saved, I would suggest you consult with your local Cornell cooperative extension.
They will need to know specifically what kind of plant it is (spiral is a topiary shape -- it might be a spruce or juniper or some other evergreen) and would likely find photos of the overall plant and also closeups of the damage helpful. They might also appreciate a sample of the affected foliage enclosed in a plastic bag and kept cool so it stays fresh.
I'm sorry I can't be more helpful long distance. Good luck with your topiary!
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