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Insecticidal soap (potassium salts of fatty acids or alkanolamine salts of fatty acids)

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Insecticidal soap may be used to control aphids
Photo: André Payette

Caution
The information below is intended only as a guide. Always read product labels carefully.

Product description

Pesticides with insecticidal soap as the active ingredient consist of salts of fatty acids (potassium or alkanolamine salts) selected for their effectiveness. These products pose a lower risk of toxicity to plants (phytotoxicity) than home remedies.

These pesticides are available ready to use or as liquid concentrates to be diluted before use.

Target pests

Products with insecticidal soap as the active ingredient may be used to control various pests, including:

NB: The product label lists the plants on which the pesticide may be used, along with the target organisms. 

How it works

Insecticidal soap works on contact. The salts of fatty acids penetrate the insect's cuticle (exoskeleton) and interfere with the structure and permeability of cell membranes. The cell contents leak from the damaged cells, causing the insect to become dehydrated and quickly die. The soap is effective only when wet.

Application

The pesticide must be sprayed directly onto pests or applied to the plant parts attacked by pests (stems and upper and/or lower leaf surfaces).

Since the product loses its insecticidal action once dry, it is best to apply it when conditions are such that it will dry slowly, i.e., early in the morning or evening or on a cloudy day. Avoid applying it on very windy days.

Precautions

The pesticide may irritate the skin and eyes, so it is best to wear gloves, long sleeves and pants and goggles when applying it.

It may be phytotoxic to some susceptible plants, including nasturtiums (Tropaeolum spp.), impatiens (Impatiens spp.), sweet peas (Lathyrus odoratus) and ferns. Symptoms may include yellow or brown spots on foliage, burns along leaf edges or burned foliage. If in doubt, it is best to spray a small area of the plant and wait 24 to 48 hours to see how it reacts.

To minimize the risk of phytotoxicity, it is best not to apply the product in full sun or to plants subject to stress (drought, extreme heat, etc.).

Pesticides with insecticidal soap as the active ingredient are not selective and can therefore harm beneficial organisms (parasitic or predatory insects, predatory mites, etc.).

Do not use near any body of water or wetland, or dump any pesticide or rinse your equipment there, as this will contaminate the water. Never dump pesticides down sewers.

Keep out of reach of children.

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