Backgrounder: Proposed Special Review Decisions for Squash Bee Exposure to Neonicotinoids


June 29, 2021

Today, Health Canada is publishing the proposed special review decisions for potential risks related to squash bee exposure to neonicotinoid pesticides imidacloprid, clothianidin, and thiamethoxam that are registered for use on cucurbits (e.g., pumpkins and squash). These special reviews were initiated in 2014.

The impact of all three neonicotinoids on pollinators has been studied by Health Canada for many years. In 2019 following public consultations, Health Canada published the final re-evaluation decisions related to potential risk to pollinators from the use of three neonicotinoid pesticides (RVD2019-04, RVD2019-05, and RVD2019-06), including squash bees, which considered the potential risks to them from uses on cucurbits. As part of the pollinator assessment, Health Canada put in place restrictions on the use of neonicotinoids to protect bees and other pollinators.

For these proposed squash bee special review decisions, the department considered the assessments on pollinators, all relevant registrant submitted data, and open literature, including the semi-field hoop house study that was started by a group of researchers in Ontario in 2017.

In the hoop house study, the scientists housed the squash bees inside a structure the shape of a half-circle, commonly used for greenhouses, and studied the impact of imidacloprid as a soil treatment, and thiamethoxam as a seed treatment, on the bees for a few years.

The bees could not escape to gather nectar or pollen to eat, or nest anywhere else outside of the hoop houses. The scientists observed their lifecycles and how they fed, mated, nested and reproduced under the exposure of the pesticide treatment applied.

Scientific assessments conducted as part of these special reviews have shown that when these neonicotinoids are used on cucurbits, the risks to squash bees are considered acceptable when applied according to the mitigation measures described in the 2019 pollinator re-evaluation decisions of these pesticides. These measures have already been implemented.

These risk mitigations included:

  • Cancellation of soil applications of imidacloprid and thiamethoxam on cucurbits;
  • Reduction of foliar (leaf based) applications of clothianidin to cucurbits to a single pre-bloom application only.

Before making the final squash bee special review decisions of clothianidin, thiamethoxam and imidacloprid used on cucurbits, Health Canada will consider all comments received from the public in response to this consultation document.

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