Natural pesticides for plants are an excellent choice for home gardens and vegetables you eat, as long as you know what works on each pest and how to use it correctly. Most natural pesticides work by contact, so they must reach the insect itself, and they have little residual effect.
This article explains the main natural and relatively safe pesticide types, what they kill, how to use them, and the mistakes that burn plants.
Before you start: natural does not mean risk-free
- Natural pesticides are usually less harmful to people and the environment, but they can burn plants if the dose is too strong or they are sprayed in the heat.
- Some harm bees if sprayed during flowering while bees are active.
- Always follow the label, and test on two leaves before spraying the whole plant.
Types of natural pesticides for plants
Potassium soap
- Kills soft-bodied insects on contact: aphids, whitefly, mealybugs, thrips and spider mites.
- Dissolves the waxy coating on the insect so it dries out and dies.
- It must reach the insect, so focus on the undersides of leaves.
- Repeat every 5 to 7 days because eggs are not affected.
Horticultural oils
- Smother scale insects, mealybugs, mites and eggs.
- Excellent in winter on deciduous trees, and at a diluted rate in summer as per the label.
- Do not spray in extreme heat, and do not mix or apply close to sulphur.
Agricultural sulphur
- One of the oldest treatments for powdery mildew and mites.
- Applied as dust or spray depending on the product.
- Do not use above roughly 32 °C, or within two to three weeks of an oil spray.
Spinosad
- A substance of natural origin produced by a soil bacterium.
- Strong against caterpillars, thrips, leafminers and Tuta.
- Spray in the evening after bees have returned, because it harms bees while wet.
Beneficial bacteria (Bt)
- Bacteria that infect caterpillars only, and are safe for people and animals.
- The caterpillar must eat the sprayed leaf, so spray early on young caterpillars.
Neem oil
- Repels insects and disrupts their feeding and growth, useful against aphids and whitefly.
- It works more slowly and needs repeating.
Yellow sticky traps
- No pesticide at all, catching whitefly, winged aphids, fungus gnats and thrips.
- Useful for monitoring so you know when an infestation starts.
Which natural option for each pest?
| Pest | Natural option |
|---|---|
| Aphids | Potassium soap or neem oil |
| Whitefly | Potassium soap + yellow traps |
| Mealybugs | Potassium soap, then horticultural oil |
| Scale insects | Horticultural oil |
| Spider mites | Sulphur or potassium soap |
| Powdery mildew | Agricultural sulphur |
| Caterpillars and thrips | Spinosad, or Bt for caterpillars |
For details on each pest: Aphids, Whitefly, Mealybugs, Spider Mites, Powdery Mildew.
Home recipes: do they work?
- Washing-up liquid: can kill aphids, but contains detergents and fragrances that burn leaves. Agricultural potassium soap is safer.
- Garlic and chilli: repel some insects temporarily, with weak results on heavy infestations.
- Vinegar: burns plants and we do not recommend it on leaves.
- A strong water jet: knocks aphids and mites off leaves, a simple first step worth trying.
How to spray natural pesticides correctly
- Spray early morning or evening so leaves do not burn.
- Wet the undersides of leaves, where most insects are.
- Repeat every 5 to 7 days, two or three times.
- Do not spray a thirsty plant; water it the day before.
- Do not mix two natural products without a test.
When do you need a chemical pesticide?
- When the infestation is very heavy and spreading fast.
- With difficult pests such as red palm weevil or nematodes.
- If you have tried a natural option two or three times without results. For the right choice, see Fungicides.
Products from Orkida
- Biobest yellow roller trap
- Plant Care potassium soap
- Universal 960 horticultural oil
- Deltasad 480 spinosad
- SAF granular agricultural sulphur
- DiMartino sulphur duster (Italy)
Natural pesticide FAQs
What is the strongest natural pesticide for plants?
There is no single answer. Potassium soap is the strongest choice for soft insects, oil for scale, sulphur for powdery mildew and spinosad for caterpillars and thrips.
Are natural pesticides safe on vegetables we eat?
Most have short pre-harvest intervals, but always wash vegetables and follow the waiting period on the label before harvest.
Why didn't the natural pesticide work?
Usually because it did not reach the insect under the leaves, was not repeated, or the infestation was too heavy. Natural pesticides need full coverage and repetition.
Can I use natural pesticides on house plants?
Yes, and potassium soap is one of the most suitable indoors; test it on one leaf first and keep the plant out of direct sun after spraying.