Ivory dish liquid is said to give insects a detour somewhere else...it won't kill them. They just don't prefer the taste of dishliquid.
In hydro, it is said to help keep fungi down.
...dishliquid is also said to make water wetter. (example) ...if you over dry your plants, it can be hard to saturate your soil, the water will run down the sides and out of your pots. This would be a good time to use dish liquid, it helps water penetrate your soil quicker/better.
...you want to use biodegradable dish liquid, btw. Doesn't have to be Ivory only, that's just what I use.