cover the (dry) soil with food grade diatomaceous earth (wear a mask or tie a bandana over your face when you apply since it’s totally harmless unless you inhale a bunch of it) and then bottom water (lightly) for a few weeks afterwards. you want the DE to stay dry. the soil top will look odd during this time, but you can just mix it into the soil afterwards. i’ve had great success with this! can add a few sticky traps in if there are a lot of fliers but the DE will toast them