Bugwiz.com* provides recipes for several easily made sprays to target spotted lanternflies. They suggest mixing 1 cup of dish soap with 1 cup of water in a spray bottle. The soap can be rinsed off the plants later with a hose. Undiluted white vinegar works well too.
*Anthony Soon, August 25, 2019, "How to Get Rid of Lanternflies Naturally (Ultimate Tutorial)," https://bugwiz.com/get-rid-of-lanternflies/