Neem oil works on aphids, scale insects, whitefly, thrips and spider mite, and it works in three ways at once: it smothers the mobile stages, it disrupts moulting in the young ones, and it keeps adults off treated foliage. You apply it at dusk or before sunrise, never in full sun and never above 30 °C, every seven to ten days until numbers drop. But before you buy a bottle, there is something almost nobody writes down: neem oil and azadirachtin are not the same product, and the difference is a legal one — and it does not read the same on both sides of the Channel.
Neem oil or azadirachtin: the difference that decides what you may do
Azadirachtin is the active substance extracted from the seeds of Azadirachta indica. Neem oil is the oil pressed from those same seeds, and it contains some azadirachtin — a variable amount, undeclared and unguaranteed.
Everything else follows from that.
| Neem oil sold as a tonic | Registered azadirachtin product | |
|---|---|---|
| What the label says | “plant tonic”, “leaf shine”, “strengthener” | an authorisation or registration number |
| What you may claim it does | improves the plant’s condition | controls a named pest |
| Azadirachtin content | variable, not guaranteed | declared and constant |
| Use in the field | as a tonic only | as an insecticide, with dose and harvest interval |
| On a crop you will sell | yes, but it is not a treatment | yes, following the label and your spray record |
In practice: oil sold as a tonic, a leaf shine or a cosmetic cannot be used as an insecticide. That is not pedantry. Under EU and UK plant protection law it is the claim that decides the category: the moment a product is offered for controlling a pest, it is a plant protection product, and it needs an authorisation to be sold or applied.
Where you are changes what you may spray
This is the part most articles skip, and it matters more than the dose.
In the European Union, azadirachtin is an approved active substance. Products based on it are authorised country by country: NeemAzal-T/S, for example, is registered in Italy, Germany, Poland and Spain, is listed for organic production, and carries a full label with crops, pests, doses and pre-harvest intervals. The EU approval of azadirachtin currently runs to 31 January 2027, with the renewal assessment still under way — which is where the annual rumour of a “ban” comes from. Nothing has been withdrawn. What does change, and changes often, is the list of crops and pests each individual product covers. You check that on the label, product by product.
In the United Kingdom, the position is the opposite and it surprises people. No neem or azadirachtin product holds a UK authorisation as a pesticide. Selling or using one for plant protection is unlawful, and the bottles you can still find online are sold as leaf shine, plant tonic or skincare. That labelling does not make them legal to spray on your plants for pest control — it only moves the offence from the seller to you.
If you garden or farm in the UK and want something lawful for soft-bodied pests, the basic substances list under Article 23 of Regulation 1107/2009 — retained in UK law — includes soft soap, sodium bicarbonate and a few others, and authorised products based on fatty acids or plant oils are available. They are less elegant than neem. They are also legal.
Reading a label in thirty seconds
- Authorisation number. Present? It is a plant protection product. Absent? It is a tonic, and the two worlds do not mix.
- Crops listed. Is your pear tree there, or does the label only mention protected vegetables? Outside that list, the use is not permitted.
- Pests named. Neem is not broad-spectrum. It is good on soft-bodied insects and poor on everything else.
- Dose and water volume. Volume matters more than concentration. Poor coverage is the single most common reason people say “it didn’t work”.
- Pre-harvest interval. How many days between the last spray and picking.
- Maximum number of applications per season.
What it actually controls
Neem acts by contact and ingestion on soft-bodied insects, and it is far better on juveniles than on adults.
- Aphids: good, especially if you catch the first colonies and wet the underside of the leaves.
- Scale insects: good on mobile crawlers, close to useless on adults already under their shield. Timing is the whole story.
- Whitefly: good, with repeat applications, because generations overlap.
- Thrips: partial. It helps, but on its own it will not hold a high population.
- Spider mite: partial, and it needs humidity and predators alongside it.
- Caterpillars, shield bugs, adult beetles: effectively nothing. Anyone selling it to you for these is selling you something else.
When to spray, and the three mistakes that scorch leaves
Time of day. Dusk or before dawn. Azadirachtin breaks down under ultraviolet light, so a midday spray loses most of its effect within hours — and the oil itself heats the leaf under strong sun and burns it.
Temperature. Do not spray above 30 °C. Below 15 °C the effect slows right down.
Interval. Every seven to ten days, two or three times. Neem has no persistence. One pass closes nothing.
The three mistakes we see most often in the field:
- Spraying in full sun: scorch on young leaves, and almost no effect.
- Tank-mixing with copper or sulphur without checking compatibility: the mix can turn phytotoxic.
- Wetting only the upper leaf surface: aphids, whitefly and mite live underneath. Miss them and you miss the treatment.
One standing caution at flowering: spray before the flowers open, or when no bees are flying. Neem is low-toxicity for pollinators, but “low” is not “none”.
Where reading the plant comes in
Neem does not resolve an infestation. It contains one. What decides whether a plant comes through is the condition it was in when the pest arrived.
A plant under water stress produces more concentrated sap, and that is exactly what aphids are looking for. Anyone who works a block knows it: the colonies always show up first in the rows that are struggling. The plant says so before the leaves do — sap flow drops days ahead of any visible symptom, and that window is when you can still fix the irrigation instead of chasing the pest.
That is the job the Plantvoice sensor does: it reads sap flow and sap salinity inside the trunk continuously, and turns those numbers into one instruction — irrigate now, or wait. On orchards using it, sap-based scheduling has cut water use by up to 40% while holding fruit quality. If you want to understand how stress is read before it shows, we have written about detecting it before the symptoms appear and about how the sap flow sensor works.
Frequently asked questions
What is neem oil used for on plants? Soft-bodied insects: aphids, scale insects in their mobile stages, whitefly, and partially thrips and spider mite. It works by contact and ingestion, smothering mobile stages and disrupting moulting in juveniles. On caterpillars, shield bugs and adult beetles it is effectively useless.
Can I use neem oil as an insecticide? Only if the product in your hand carries an authorisation number as a plant protection product. In the EU such products exist and are registered country by country. In the UK none is authorised, so neem sold as leaf shine or a plant tonic cannot lawfully be used for pest control.
Is neem oil banned in the UK? Neem oil is sold in the UK, but not as a pesticide: no azadirachtin product holds a UK plant protection authorisation, so using one to control pests is not permitted. The “plant tonic” label on the bottle does not change that.
When should neem oil be applied? At dusk or before dawn, never in full sun and not above 30 °C, repeating every seven to ten days for two or three applications. Ultraviolet light degrades azadirachtin within hours.
Does neem oil burn leaves? It can, if you apply it with the sun high, at high temperatures, or mixed with incompatible products. Applied in the evening at label rate on listed crops, the risk is low.
Want to reach pest season with plants that can take it? Talk to our agronomists about setting up monitoring in your orchard, or ask for a Plantvoice sensor trial on your own trees.
HERO_PROMPT: Ultra-realistic editorial photograph of a farmer’s hands holding a small amber glass bottle of neem oil next to a hand sprayer, on a wooden bench in a sunlit orchard. Extreme detail on the oil droplets and the bottle glass: visible texture, natural imperfections, true-to-life colour. Shot on a full-frame DSLR, 85mm lens, shallow depth of field with clean bokeh, soft natural daylight with golden-hour warmth, high dynamic range, realistic shadows and highlights, subtle analogue film grain (Kodak Portra 400), cinematic colour grading, elegant editorial composition, agricultural documentary aesthetic, photorealistic, ultra-detailed, 8K, masterpiece quality. No text, no watermark, no logo, no captions, no cartoon, no 3D render, no illustration, no AI-glossy plastic look, no oversaturated colours, no human faces in focus, no branded products or readable labels.
