Try using 800ml of JWA, 60g of NaOH, 60g of clay based on 20L.

This recipe is sure to subdue even the most difficult pests, the thrips.
Soft water must be used for water. And add NaOH by pre-dissolving it in a little water. Clay is also added by dissolving it in water beforehand. Depending on the crop, it may cause concentration disturbance. Partial testing is required beforehand.
There are no Japanese beetles in Korea, so I couldn't test it myself.
When spraying this pesticide, be careful not to come into contact with the skin.