cherry laurel problem
This sounds like white prunicola scale. They are insects that feed on the plant sap and they are a very common problem on cherry laurels. We see infestations like this a lot.
First, read through our webpage to understand the life cycle, which will help you target sprays if that is the course you want to take. https://extension.umd.edu/hgic/topics/armored-hard-scale-trees-and-shrubs
Take a look at our blog posts on cherry laurel and white prunicola scale for photos and treatment. When there is a heavy infestation of white prunicola scale and dieback is severe, it may be best to remove the shrub altogether rather than try to treat it. Depending on where the infestation is located, you may be able to prune out branches selectively and discard them. https://marylandgrows.umd.edu/2019/09/25/qa-what-is-this-white-growth-on-my-cherry-laurel-shrub/
and our blog post on how to grow cherry laurels in your landscape https://marylandgrows.umd.edu/2019/01/07/qa-whats-wrong-with-my-cherry-laurel-shrubs/