Thank you for the information on neem oil and toxicity to bees.

There seems to be a volume of information conveying different messages, even from credible sources. Scientific research is very important in determining effects of a chemical, but methods and results vary (lab vs. field, mode of exposure, etc.), and we rely on experts to synthesize the information and make general statements for the label. Even statements on labels vary due to chemical concentration or mode of application.

When using any pesticide please remember the following:

• Read and follow the label and don’t spray a higher concentration or with greater frequency than is needed.
• Avoid spraying bees directly by spraying in the evening after they have gone.
• If you are still concerned, avoid spraying flowers that bees are expected to visit in the next few days.

The Xerces society has a publication on minimizing risk to bees with organic pesticides which might suggest alternatives: http://www.xerces.org/wp-content/uploads/2009/12/xerces-organic-approved-pesticides-factsheet.pdf.  They place neem as low in toxicity, with similar recommendations.

Be cautious and informed. Many new labels for neem do contain a warning of toxicity and indicate a short residual toxicity. Furthermore, there has been a recent recall of some neem products in Oregon as there were traces of synthetic pesticides, presumably the result of poor manufacture methods.

Thank you for using Ask an Expert!

-Carolyn Breece with special thanks to Louisa Hooven and Andony Melathopoulos of Oregon State University