Neem oil: what it kills and what it harms
'Neem oil' on a label means one of two products. Clarified hydrophobic neem oil, the usual garden spray, is an oil that smothers mites and soft-bodied insects it coats and also controls powdery mildew. Azadirachtin, the active extract that is taken out of the oil, is an insect growth regulator: young insects die at their next moult, and adults are not controlled. Both break down within days. The neem-oil label warns that it is toxic to bees sprayed directly.
Also sold or listed as: azadirachtin, neem, clarified hydrophobic neem oil.
At a glance
- Active
- Azadirachtin and clarified hydrophobic neem oil
- Residue
- Short: hours to days for both forms (UC IPM). Azadirachtin's half-life on leaves is 1–2.5 days (NPIC).
- Caution
- 5 of 7 beneficials
- Safe
- 2 of 7 beneficials
What it works on
- Spider mitesOn the neem oil label. In a Kansas State greenhouse test, clarified hydrophobic neem oil killed over 80 % of twospotted spider mites.
- AphidsOn the label. It kills only the aphids present on the day it is sprayed (UC IPM). In the same Kansas State study, none of the plant-oil products tested gave sufficient control of green peach aphid 7 to 21 days after spraying (the study summary does not say whether the neem product was in that trial).
- WhitefliesOn the label. In the Kansas State study, none of the plant-oil products tested gave sufficient control of sweetpotato whitefly (the summary does not say whether neem was in that trial). The AzaGuard label aims azadirachtin at the whitefly larvae and pupae.
- ScaleOn the label, alongside dormant sprays for overwintering eggs on fruit and shade trees.
- Leafminers, thrips and caterpillarsAzadirachtin products (for example AzaGuard) target the larvae and nymphs. They do not control adults.
- Powdery mildew, rust and black spotThe neem oil label is also a fungicide label, at 2 tbsp per gallon every 7 to 14 days.
Effect on beneficials
- Phytoseiulus persimilisUC IPM rates neem oil moderate and azadirachtin low to moderate for predatory mites. Its figures come from the western predatory mite, a relative, and are averages. We found no trial on P. persimilis itself. UC moderate → caution. — UC IPM floriculture relative toxicities table (2022)Caution — moderate, 25–75 %
- Amblyseius cucumerisUC IPM rates predatory mites moderate for neem oil and low to moderate for azadirachtin. In a Florida lab test, residues of an azadirachtin + pyrethrin mix significantly reduced survival of N. cucumeris and two other predatory mites after 72 h of exposure. That was a mixture, not neem alone. UC moderate → caution. — UC IPM floriculture relative toxicities table (2022); Busuulwa et al. 2024, J Econ EntomolCaution — moderate, 25–75 %
- Aphidius colemaniUC IPM rates parasitic wasps moderate for neem oil and moderate to high for azadirachtin, so azadirachtin products may be harder on them. We found no trial on A. colemani. UC moderate → caution. — UC IPM floriculture relative toxicities table (2022)Caution — moderate, 25–75 %
- Encarsia formosaUC IPM rates parasitic wasps moderate. In a Pakistani cotton study, a neem seed-oil extract killed under 30 % of Encarsia formosa pupae and adults and was classed harmless. That was a different product from US neem oil, so this keeps UC's moderate → caution. — UC IPM floriculture relative toxicities table (2022); Gogi et al. 2021, Sci Rep 11:2101Caution — moderate, 25–75 %
- Chrysoperla carneaAn azadirachtin product was harmless to newly emerged adults by residue, spray or feeding. But females that ate it laid fewer eggs until the effect wore off. Larvae were not tested. UC IPM rates general predators moderate → caution. — Medina et al. 2004, J Econ Entomol 97:43; UC IPM floriculture relative toxicities table (2022)Caution — moderate, 25–75 %
- Orius insidiosusIn a Kansas State lab test, azadirachtin was minimally harmful to adults (80–100 % survival after 96 h), and the survivors still killed thrips. The test used azadirachtin only; UC rates neem oil moderate for general predators. — Herrick & Cloyd 2017, J Econ Entomol 110:931Safe — low toxicity, under 25 % effect
- Samurai waspFemales kept for 7 days on dried azadirachtin residue at the field rate: 3.1 % mortality, no different from water. This is a residue test; a direct spray was not tested. — Chierici et al. 2025, Sci Rep 15:4622Safe — low toxicity, under 25 % effect
No data never means safe: treat an unrated pairing as caution and try it on a small area first. See every product side by side →
How it works
Neem oil is pressed from the seeds of the neem tree. Its most active part, azadirachtin, can be extracted, and what is left is called clarified hydrophobic neem oil (NPIC). Most bottles hold one or the other. Neem Oil 70% (EPA Reg. 70051-2) is 70 % clarified oil, while AzaGuard (EPA Reg. 70299-17) is 3 % azadirachtin. Check the active-ingredient line.
Clarified neem oil acts like other horticultural oils. It is a contact spray that smothers what it coats, and it has fungicide activity too. Colorado State notes that this oil fraction is mostly free of azadirachtin.
Azadirachtin works differently. It reduces feeding and repels, and it blocks the moulting hormone (ecdysone), so larvae and nymphs die at their next moult (NPIC; AzaGuard label). It works slowly and does not control adults.
Neither form lasts. UC IPM gives both a short duration of hours to days, and azadirachtin's half-life on leaves is 1–2.5 days (NPIC). That is why the labels repeat sprays every 7 to 14 days.
Using it
- Rate (neem oil)
- For insects and mites, 2–4 tbsp (1–2 fl oz) per gallon of water, or ½–1 tbsp per quart. For diseases, 2 tbsp per gallon. Spray every 7 to 14 days, and weekly under heavy pressure (Neem Oil 70% homeowner label, EPA Reg. 70051-2).
- How to spray
- Wet all surfaces, including the undersides of leaves, and keep mixing as you go. Do not add spreaders or stickers. Spray early in the morning or late in the evening to limit leaf burn.
- Houseplants
- The label covers houseplants for indoor and outdoor use, and as a leaf polish on hardy plants. Clemson notes that only a few pesticides are labelled for indoor use, so check yours. You can also spray outdoors in mild weather and bring the plant in once dry. NPIC describes a garlic or sulfur smell.
- Azadirachtin products
- AzaGuard recommends 2 to 3 sprays 7 to 10 days apart, aimed at young stages. Use the mixed spray within 8 hours.
- Re-entry and harvest
- The restricted-entry interval is 4 hours on both the Neem Oil 70% and AzaGuard agricultural labels. Both may be used up to the day of harvest.
- Mixing
- The neem oil label says to avoid tank mixes with sulfur, captan and several other fungicides. Test any mix on a few plants first.
Cautions
- Bees
- The neem oil label reads: 'This product is toxic to bees exposed to direct treatment. Do not apply this product while bees are actively visiting the treatment area.' NPIC calls neem oil practically non-toxic to bees, because insects must eat treated plants. UC IPM's bee rating is II: do not spray flowering plants, except between sunset and midnight where the label allows.
- Bumblebees and azadirachtin
- In a lab study, bumblebee microcolonies fed azadirachtin in sugar water produced no offspring above 3.2 mg/L. The maximum field concentration was 32 mg/L (Barbosa et al. 2015). Keep it off open flowers.
- Fish
- The label says the product is hazardous to fish and aquatic invertebrates. NPIC rates neem oil slightly toxic to fish and azadirachtin moderately toxic. Do not spray near ponds or drains.
- Pets
- Outside the US, neem oil used on cats for fleas caused drooling, trembling and convulsions, and some cats died (NPIC). Never use a plant spray on a pet.
- Plant burn
- Do not spray wilted or stressed plants or new transplants. Test first on impatiens, fuchsia and hibiscus flowers, some rose flowers, ornamental olive and some carnations (label; Colorado State lists the same plants).
- With released beneficials
- The label itself says to run a small trial for compatibility first when you use it alongside beneficial insects.
Use instead
- Spider mites under glass or indoors: release Phytoseiulus persimilis.
- Aphids: insecticidal soap, which leaves no residue, or Aphidius colemani in a greenhouse.
- Greenhouse whitefly: Encarsia formosa.
- Scale and overwintering eggs on trees: a dormant horticultural oil spray.
- Caterpillars: Bt kurstaki, which affects only moth and butterfly larvae.
Other products
Sources
NPIC, Neem Oil General Fact Sheet (Bond, Buhl & Stone, 2012)
EPA label, Neem Oil 70% (Certis), EPA Reg. 70051-2, revision 2023-02-07
EPA label, AzaGuard (BioSafe), EPA Reg. 70299-17, 21 July 2020
UC IPM, Relative toxicities of pesticides used in floriculture to natural enemies and honey bees (2022)
UC IPM Pest Notes: Aphids, UC ANR Pub. 7404
Colorado State University Extension, Insect Control: Horticultural Oils, fact sheet 5.569
Clemson HGIC 2252, Common Houseplant Insects & Related Pests (rev. 2021)
Cloyd et al. 2009, Plant-derived essential oil products on arthropod pests. J Econ Entomol 102:1567
Barbosa et al. 2015, Azadirachtin effects on the bumblebee Bombus terrestris. Ecotoxicology 24:130
Medina et al. 2004, Azadirachtin and Chrysoperla carnea reproduction. J Econ Entomol 97:43
Herrick & Cloyd 2017, Pesticide effects on Orius insidiosus. J Econ Entomol 110:931
Gogi et al. 2021, Biorationals and Encarsia formosa on Bt cotton. Sci Rep 11:2101
Busuulwa et al. 2024, Insecticide residues and predatory mites in strawberry. J Econ Entomol 117:2461
Chierici et al. 2025, Natural products vs Halyomorpha halys and Trissolcus japonicus. Sci Rep 15:4622
Drafted from the cited sources, then checked claim by claim against those sources on 23 September 2026.
Always follow the label. Labels are legally binding; this page is not.