There are insecticides that go by names like; "Natures Answers" or "Organic" and tend to be derived from plant extracts such as Pyrethroids or use fatty acids or extracts from certain oily seeds. They are not normally as effective as some insecticides but will be have a much better effect than washing up liquid.

Be sure to mix soap with anything you spray--except, of course, insecticidal soap--to get it through the "wool".

Very good point :-)