Wasps under the deck are an absolute nuisance and must be removed to make your outdoor space safe and useable. There are a variety of effective means to get rid of the wasps, some of which use chemicals, and others use natural products.
You will likely discover wasps nesting under your deck when it is inconvenient and when you want to use your outdoor area. No amount of waving your arms around or swatting at them with your book will get them to leave.