Bees may be exposed to neonicotinoids in numerous ways, including direct contact with spray residue on plants or through ingestion of pollen or nectar. Other flower-visiting insects, including butterflies, flies, and beetles—many of which are pollinators—can also be affected in this way.

Because these chemicals are systemic and absorbed into plant tissues, insects that rely on nectar, pollen, or other floral resources have increased oral exposure to residues of neonicotinoids or their metabolites. Residues have been recorded in pollen (Laurent and Rathahao 2003; Bonmatin et al. 2003, 2005a), nectar (Schmuck 2001; Krischik et al. 2007), and to a much lesser degree, other plant exudates (Girolami et al. 2009). Residues are also found in contaminated dust released from seed planting equipment (Greatti et al. 2006; Krupke et al. 2012; Tapparo et al. 2012) and in weeds growing within or adjacent to treated fields (Krupke et al. 2012).

Another issue arising from the systemic action of neonicotinoids is that they remain toxic within the plant for longer than other insecticides. Evidence suggests that systemic insecticides may remain in plant tissues for months or even more than a year (e.g., Maus et al. 2005). In addition, some neonicotinoids can persist for extended periods in soil (see table 3.1) (Rouchaud et al. 1996; Maus et al. 2004a, b). Clothianidin, for example, has a soil half-life of 148 to 1,155 days (51⁄4 to 381⁄2 months) depending upon soil types (EPA 2003a). Untreated plants may take up residues of neonicotinoids still present in the soil from previous applications (Bonmatin et al. 2003, 2005b).

The presence of systemic insecticides in plants poses a particular risk to bees, because they feed on nectar as adults and collect nectar and pollen to feed their offspring.

Honeybees, native bees and other pollinators are responsible for 1 out of every 3 bites of food we eat. Bees pollinate 71 of the 100 crops that make up 90% of the world’s food supply. Many fruits and vegetables, including apples, blueberries, strawberries, carrots and broccoli, as well as almonds and coffee, rely on bees. These beneficial insects are critical to maintaining our diverse food supply. Honeybee populations have been in alarming decline since 2006. Widespread use of a neonicotinoids is a significant contributing factor. In addition to killing bees outright, research has shown that even low levels of these dangerous pesticides impair bees’ ability to learn, to find their way back to the hive, to collect food, to produce new queens, and to mount an effective immune response.

Therefore, we consumers, gardeners, and bee-keepers together, urge retailers in Canada to do the right thing.