Unpacking the Standards: Bloom-Time Ban on Pesticide Applications


Bee Better Certified growers use management practices that improve the resilience of their crops and reduce the likelihood of pest outbreak. They also keep track of pest populations on their farm through scouting and monitoring to know when, and if, a pesticide or other intervention is needed to manage a problem that poses economic harm to their crop.  

While the Bee Better Certified Production Standards allow pesticides to be used in direct response to pest outbreaks, many of these pesticides can have negative impacts on wild and managed bees living and foraging in and around treated crops. In addition to encouraging growers to adopt preventive pest management practices, the Standards limit or prohibit certain uses and timing of pesticide applications to minimize potential harm caused by  exposure to bee-toxic pesticides

The most obvious way bees can be exposed to pesticides is by direct contact with treated crops. Depending on the toxicity of the pesticide, and the rate at which it has been applied, direct exposure can kill bees foraging in crop fields during or shortly after a pesticide application. 

Avoiding the application of bee-toxic pesticides when bees are active in crop fields is the easiest way to protect bees and other pollinators  on farms. The Bee Better standards therefore include bloom-time restriction for pesticides that are rated as level I under the Bee Precaution system maintained by the University of California Statewide Agricultural and Natural Resources IPM Program, as well as fungicides that may negatively affect bees. 



A wild bee (Andrena sp.) visiting a highbush blueberry bloom.  Photo:  Emily May (Xerces Society)


What are the Bee Better standards for pesticide use during bloom?

The Bee Better standards prohibit the use of pesticides rated as level I under the Bee Precaution system maintained by the University of California Statewide Agricultural and Natural Resources IPM Program during bloom for crops that are visited by or pollinated by insects (Standard 2.2b; see Appendix K for list). In addition, Bee Better prohibits foliar applications of certain fungicides during bloom for these same crops (Standard 2.1b; see Appendix K for list). These chemicals are prohibited from the time the first crop blooms until petal fall or until all blooms have closed (for example, squash plants have blossoms that close shortly after bloom but do not drop off the plant until days later). 


How can I find out which products are restricted under this standard?

The Bee Better Production Standards have lists of the pesticides prohibited from use during bloom in Appendix K. If you’d like to get more detailed information about the toxicity of different active ingredients or specific products, Appendix M provides step-by-step instructions for using the online Bee Precaution tool managed by the University of California Statewide Agricultural & Natural Resources Integrated Pest Management Program (UC IPM). 


What crops does the  bloom-time ban apply to? 

Any crop that blooms before harvest and is visited by or pollinated by insects. Many wind-pollinated or self-pollinated crops, such as amaranth, barley, oats, and wheat, are exempt from this standard; however, the bloom-time ban still applies to a few wind- or self-pollinated crops known to be visited by bees for pollen or nectar provisions, such as corn and soybeans. Crops that are harvested and killed before bloom, such as certain leafy vegetables and brassicas, are also exempt (see Appendix L for the list of exempt crops.)


What about other exposure routes?

Bees can be exposed to pesticides in many ways outside of direct application during bloom: they can be exposed via drift onto hives, drift onto or leaching of systemic materials into flowering plants in field margins, pesticide residues on plant surfaces, or contaminated water sources. Developing larvae can have long-term exposure to low levels of agricultural chemicals over the course of days to weeks when fed on contaminated pollen and nectar brought back to the nest or hive. We will explore how Bee Better standards mitigate risk from other exposure routes in future blog posts in this series.


For more information on minimizing pesticide risk to bees, see the following resources:

University of California IPM Bee Precaution Pesticide Rating. http://www2.ipm.ucanr.edu/beeprecaution/

Johansen, E., L.A. Hooven, and R.R. Sagili. 2013. How to Reduce Bee Poisoning from Pesticides. Oregon State University Extension.  https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/pnw591.pdf 

May, E., J.K. Wilson, and R. Isaacs. 2015. Minimizing Pesticide Risk to Bees in Fruit Crops. Michigan State University Extension. http://bit.do/E3245 

Code, A., H. Sardinas, T. Heidel-Baker, J.K. Cruz, S.H. Black, E. Lee-Mader, M. Vaughan, and J. Hopwood. 2016. Guidance to Protect Habitat from Pesticide Contamination. The Xerces Society for Invertebrate Conservation. https://xerces.org/publications/fact-sheets/guidance-to-protect-habitat-from-pesticide-contamination

Vaughan, M., G. Ferruzzi, J. Bagdon, E. Hesketh, and D. Biddinger. 2014. Preventing or Mitigating Potential Negative Impacts of Pesticides on Pollinators Using Integrated Pest Management and Other Conservation Practices. USDA Agronomy Technical Note no. 9. https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=34828.wba