I would recommend Safer's insecticidal soap (concentrate, not RTU). Apply it with a tank sprayer, since the RTU in a squirt bottle is very tedious to apply and takes as long as squishing.

I have successfully used 3-4 TSP of liquid dish soap per gallon. However, you don't know exactly how much to use, as some are more dilute than others, and formulas change over the years. Also these contain sodium rather than Safer's potassium; Safer's is better for the plants and garden.

Allow 24 hours to kill and then check for effectiveness.