You can use dish detergent, like Dawn or Ivory, to kill bugs in your garden and plants. Add about five tablespoons of soap per one gallon of water, or make half that much or a fourth that much if you only need it.
The soap is non toxic to you and shouldnt give you dishpan hands either. I use a small squirt bottle, but a pump up sprayer will work also, the one liter size.
The mixture has to get on the bugs while its wet. Onc ethe mixture dries it is no longer functional for insect killing. Make sure you spray the whole plant, underneath, the bottom, at junctions in the stems and leaves etc.
The spray mixture can be applied once a week, between, or before watering, to help wash away excess soap. A couple tablespoons of soap isnt going to make a big difference in phosphates in the waterways, as opposed to washing clothes and having it dump into the wastewater/drainage.
Water your plants to rinse off soapy reside. I wash my vegetables and fruits before I eat them anyway, using dish detergent normally.