Is Neem Oil Safe for Bees?
Not reliably. Neem oil is lower risk to bees than many insecticides, including some organic ones, but "safe" overstates it. The Xerces Society and the University of California classify neem and its active compound azadirachtin as moderately toxic to bees, and laboratory studies have found harm to bumble bee colonies and honey bee larvae. The National Pesticide Information Center, on the other hand, calls neem oil practically non-toxic to bees. The sources disagree, and the practical answer is the same either way: never spray it on open flowers, and apply it when bees are not foraging.
What neem oil is
Neem products come from seeds of the neem tree. The National Pesticide Information Center (NPIC) explains that the most active insecticidal compound, azadirachtin, "reduces insect feeding and acts as a repellent" and "interferes with insect hormone systems, making it harder for insects to grow and lay eggs." Other components of the oil kill insects in other ways.
Products labeled as neem vary. Some are clarified hydrophobic neem oil, which NPIC describes as made of fatty acids and glycerides, with azadirachtin as a separate extract. Others are azadirachtin formulations. LSU AgCenter notes the oil itself coats insects and blocks their breathing openings, while azadirachtin acts as a feeding deterrent and growth regulator. The risk to bees is not identical across them, and most studies test one form or the other.
Where the sources disagree
| Source | What it says about bees |
|---|---|
| NPIC (Oregon State University) | "Practically non-toxic to birds, mammals, bees and plants"; insects must eat treated plant tissue, so bees "are not likely to be harmed" |
| Xerces Society | Azadirachtin and neem oil are "moderately toxic to bees and parasitoid wasps"; toxicity increases when mixed with soap |
| UC IPM Bee Precaution Ratings | Azadirachtin (Neemix 4.5) and neem oil products rated II, the middle of three levels; a neem-pyrethrin combination is rated I, the highest hazard |
| LSU AgCenter | Cites UC as rating neem moderately toxic; apply only in late evening, night, or early morning, and not on blooming plants |
The disagreement comes down to exposure. NPIC's reasoning is that neem mostly affects insects that chew treated leaves, and bees do not. That reasoning centers on direct exposure of adult bees. It does not address bees eating contaminated nectar or pollen, or feeding it to larvae, or effects on species other than honey bees. Those are the exposures the studies below examined.
What the studies found
Bumble bees
A laboratory study by Barbosa, De Meyer, Guedes, and Smagghe in Ecotoxicology fed azadirachtin to buff-tailed bumble bee (Bombus terrestris) colonies over 11 weeks. The researchers tested concentrations from 0.64 to 320 mg per liter; they cite 32 mg per liter as the maximum field concentration. At 3.2 mg per liter and above, the bees produced no offspring and worker mortality ranged from 32% to 100%. Even at the lowest dose, 0.64 mg per liter, drone production dropped significantly. Effects were worse when bees had to forage for their food.
This was oral exposure in a lab setting, which is not the same as a bee visiting a sprayed garden. But 3.2 mg per liter is one-tenth of the field concentration the authors cited, and the reproductive effects were severe.
Honey bees
A study of six botanical insecticides by Xavier et al. in the Journal of Insect Science found neem oil was among the products that killed adult honey bee workers in lab tests, increased larval mortality, produced smaller adults from exposed larvae, slowed walking, and reduced forager visits. The authors concluded that botanical insecticides "might generate acute toxicity and sublethal effects on honey bees," contrary to their reputation as environmentally safe.
The broader picture
A 2023 review in Insects by Catania et al. pulled together the research on botanical pesticides and bees. For azadirachtin, lab studies generally showed high mortality in honey bee larvae and adults, while field results were mixed: some found no drop in foraging bees and others did. The review's overall conclusion is balanced: botanicals "cause lethal effects and a large number of sublethal effects on bees," but "the toxicity is limited when comparing the effects of these compounds with those of synthetic compounds."
That is the fairest summary available. Neem is not in the same category as broad-spectrum synthetic insecticides. It is also not harmless, and the risk is greatest for bumble bees and for developing bees fed contaminated food.
If you use neem, how to reduce the risk
- Do not spray open flowers. That includes flowering weeds under or near the target plant. Xerces recommends avoiding application when the crop or adjacent flowering plants are in bloom.
- Spray at dusk or later. Xerces and LSU both recommend applying when bees are not foraging.
- Do not add soap. Xerces notes that mixing neem with soap increases its toxicity.
- Avoid combination products. Neem mixed with pyrethrins carries UC's highest bee hazard rating, and Xerces rates pyrethrins as highly toxic to bees.
- Spot-treat. Apply only to affected plants, not the whole bed.
- Keep it away from water. NPIC rates neem oil slightly toxic, and azadirachtin moderately toxic, to fish and aquatic animals.
Lower-risk alternatives
For many of the soft-bodied pests neem targets, there are options with less risk to bees. The Xerces guide describes insecticidal soap and horticultural oil as harmful to bees only on direct contact, so applying them at night on non-flowering plants avoids most exposure. For caterpillars, it describes Bt kurstaki as having a low likelihood of harm to bees. For aphids on sturdy plants, a strong spray of water often does the job.
Better still is preventing the pest from reaching the plant. See row covers for pest control. And the broader point about organic products applies here: an organic-approved label is about how a pesticide is made, not a finding that it is safe for pollinators. Are organic pesticides safe? covers that in more depth.
Related
This page is part of No-Spray Pest and Disease Management, which puts spraying last, after exclusion, sanitation, resistant varieties, and habitat for the natural enemies that neem can also harm.