Growli
Let's go

Gardening glossary

Neem oil

Neem oil is one of the most popular "soft" pesticides in organic gardening. Extracted from the seeds of the neem tree (*Azadirachta indica*), the oil contains azadirachtin and dozens of other limonoids that disrupt insect feeding, moulting, and reproduction. Unlike a hard-knockdown synthetic, neem works slowly — most affected insects stop feeding within 24 hours but die over the following several days.

What neem oil controls:

- **Soft-bodied sucking insects** — aphids, whiteflies, thrips, mealybugs, soft scale, spider mites. - **Some leaf-feeding insects** — Japanese beetle, leafminers, sawfly larvae. - **Fungal diseases** — powdery mildew, rust, black spot, leaf spot. The fungicidal effect is from the oil component coating spores, not a true biocide. - **Soil pests** — drenched neem can suppress fungus gnat larvae and some soil-dwelling pests.

What it does not control well:

- Hard-shelled scale once mature (the wax coating blocks contact). - Caterpillars (use [Bt](/glossary/biological-control) instead). - Slugs, snails, ants, or larger pests.

How to use neem safely:

1. **Buy cold-pressed neem oil, not "clarified hydrophobic extract of neem."** The latter has had azadirachtin partially removed and is much less effective. 2. **Mix fresh.** Combine 5 ml neem oil + 2–3 ml mild liquid soap (as an emulsifier) + 1 litre warm water. Shake thoroughly until the mix is uniformly cloudy. 3. **Spray in the cool of the evening** when bees are not foraging and the sun is off the leaves. Hot midday sun + neem + waxy leaves can cause leaf burn. 4. **Cover all leaf surfaces, especially undersides.** Most pests live on the underside. 5. **Repeat every 7 days for 3 cycles** to interrupt the life cycle of the pest. 6. **Avoid during peak bloom.** Neem is moderately toxic to bees when wet; once dry on the leaf, contact toxicity drops considerably. Spray after bee activity ends for the day.

Safety profile:

- **Mammals.** EPA and EU classify neem and azadirachtin as low-toxicity to humans, pets, and livestock at typical garden concentrations. Cold-pressed neem in food-grade form has been used in traditional medicine for centuries. - **Bees and other pollinators.** Direct spray is harmful. Residues on dried leaves are much less so but can still affect bees that contact wet residue. Apply outside bloom or at dusk. - **Aquatic life.** Toxic to fish; do not spray near ponds or watercourses. - **Plant safety.** Some sensitive species (calatheas, ferns, some begonias) can scorch from neem. Test a small area first.

For a regulated, more recent alternative, some neem-derived formulations using only the azadirachtin compound (e.g. Azadirachtin EC) are available in commercial horticulture and have a more predictable dose-response than crude neem oil.

Where this comes up in our guides

Related terms

Integrated pest management (IPM)

Integrated pest management is the EPA-recognised, environmentally-sensitive framework for pest control. It combines pest monitoring, action thresholds, prevention, biological controls, and targeted chemical sprays — used only as a last resort — to manage pests with the lowest possible risk to people, beneficial wildlife, and the environment.

Biological control

Biological control is pest management using living organisms — predators, parasitoids, pathogens — instead of synthetic chemicals. Examples: ladybirds for aphids, Encarsia formosa parasitic wasps for whitefly, nematodes for vine weevil grubs, and Bacillus thuringiensis for caterpillars.

Systemic insecticide

A systemic insecticide is absorbed by the plant and moves through its tissues, killing sap-sucking insects that feed on the treated plant. Neonicotinoids are the best-known class — but they are heavily restricted in the UK and EU because of harm to pollinators. Use is now banned outdoors in the UK as of 2025.

Aphid

Aphids are tiny pear-shaped sap-sucking insects, usually green, black, or pink, that cluster on new growth and undersides of leaves. They reproduce rapidly and excrete sticky honeydew that fuels sooty mold.

Whitefly

Whiteflies are tiny moth-like insects, around 1 to 2 mm long, with powdery white wings. They cluster under leaves and fly up in a small cloud when disturbed, leaving behind honeydew and yellowed foliage.