Is Neem Oil Really Safe for Bees and Other Pollinators

To answer that question, we may need to define some terms. Are any pesticides “safe” if they are meant to kill pests? Safe for whom? Certainly not the pests! I suppose that in this case we mean “safe for pollinators”, so I’ll proceed with that working assumption. What are “conventional pesticides”? Broad-spectrum insecticides such as pyrethroids or neonicotinoids? Finally, I will assume that “neem oil” refers to cold-pressed neem oil rather than whole preparations that include water-soluble azadirachtin (MFY note: azadirachtin is neem’s primary active compound).

Oils, in general, should be considered broad-spectrum contact insecticides, which means they are toxic to most soft-bodied arthropods unlucky enough to be directly sprayed by them. Oils may suffocate insects and other arthropods by clogging spiracles (MFY note: the small breathing pores along an insect’s exoskeleton) and interfering with respiration. They also may break down the waxy layers on the insect’s cuticle (MFY note: an insect’s hard outer shell), eventually leading to desiccation (water loss) and death. Oils may also coat delicate wings, rendering insects incapable of flight. Therefore, spraying honeybees directly with any oil is likely to produce some mortality. For this reason, if one seeks to protect pollinators and other beneficial insects, then neem oil should not be sprayed on plants (especially flowering plants) actively being visited by them. Specific guidelines from the UC Statewide Integrated Pest Management Program (UC IPM) are as follows:

Do not apply or allow to drift to plants that are flowering (including weeds), except when the application is made between sunset and midnight (if allowed by the pesticide label and regulations). Do not allow pesticide to contaminate water accessible to bees, including puddles.

If compared to “conventional” broad-spectrum insecticides such as pyrethroids or neonicotinoids, neem and other oils should be expected to have less residual toxicity, meaning that honeybees or other beneficial insects landing on residues from sprays may not be negatively affected. Neem residues are considered repellent and may be potent contact irritants, however, so bee visitation to treated plants may be much reduced after spraying.

Learn more about hazards associated with neem and azadirachtin here:

• Neem oil — UC IPM active ingredient details
• Azadirachtin — UC IPM active ingredient details