Insecticidal Soap
A contact spray made from potassium fatty acid salts that kills soft-bodied insects on direct application without leaving harmful residues.
What it is
Insecticidal soap is made from the potassium salts of naturally derived fatty acids, typically derived from plant oils. Commercially available formulations are certified for organic production. It is also easily prepared at home using pure castile soap. It breaks down quickly in the environment and leaves no toxic residue.
What it does
The fatty acids in the soap penetrate the soft cell membranes of small, soft-bodied insects, disrupting their structure and causing rapid dehydration and cellular breakdown. It works on contact only and has no residual activity after drying, making it safe for beneficial insects that visit after the spray has dried.
When to use
Apply at the first sight of pest colonies, targeting aphids, spider mites, thrips, whitefly, or scale crawlers on contact. Most effective when applied directly onto the pest. Spray in the early morning or late evening to slow evaporation and maximise contact time on insects. Repeat every 4 - 7 days as needed.
When not to use
Avoid spraying plants that are drought-stressed or in direct midday sun, as phytotoxicity can occur. Do not use on ferns, succulents, very young seedlings, or hairy-leafed plants without testing on a small area first. Hard water can reduce effectiveness - use rainwater or filtered water if possible.
How to apply
- 1
Prepare a 1 - 2% solution by mixing 2-4 teaspoons of pure castile soap per quart of water. Use soft or filtered water for best results.
- 2
Shake gently to mix and transfer to a clean spray bottle.
- 3
Spray directly onto affected plant parts, thoroughly coating all pest-infested areas, especially the undersides of leaves where insects shelter.
- 4
Ensure complete coverage of the pest body surface - the spray must make direct contact to be effective.
- 5
Repeat every 4 - 7 days for two or three applications, or until pest pressure is no longer visible.
Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals - ever.