gnu- I first check for beneficial insects such as Ladybug beetles, Lacewings, etc. If none are present, water spray and soap solutions, DE, etc. as described above; regarding insecticidal soaps, only use out of direct sunlight to avoid leaf burn, and spray undersides of leaf surfaces as well as topsides.

I prefer to let the treated plant drip nearly dry in shade, then follow it up with a plain water spray to wash off the soap, honeydew (plant sap leaked by aphids can attract disease and other pests) and dead aphids. Check daily and re-treat as needed. If sooty mold develops (black fungas on aphid "honeydew"), a rag moistened with rubbing alcohol will clean it off. On woody plants, horticultural oils will effectively smother the aphids.

Pyrethrum and permethrin sprays can indeed be used to combat aphids, but are also toxic to beneficial insects. We find it most effective to begin with the least environmentally hazardous control (in this case, water spray, then soap solution) repeated as needed before using permethrin-based (or stronger) products whether from natural or laboratory sources. As they are mild carcinogesns and neurotoxins we use them rarely and with caution.