...the degree to which honey bees in our study gathered maize pollen was surprising
The finding that bee-collected pollen contained neonicotinoids is of particular concern because of the risks to newly-emerged nurse bees, which must feed upon pollen reserves in the hive immediately following emergence.
Pollen is the primary source of protein for honey bees, and is fed to larvae by nurse bees in the form of royal jelly.
A bee will consume 65 mg of pollen during the 10 day period it spends as a nurse bee , therefore a concentration of 20 ng/g (ppb) in pollen would correspond to a dose of 1.3 ng (65 mg 620 ng/g) or almost 50% of the oral LD50 of ca. 2.8 ng/bee .
Some of our pollen concentrations were even higher, although it is important to note that LD50 is measured as a one-time dose, while exposure through contaminated pollen would be spread out over the 10 d period and that there is likely substantial metabolic decay of the compounds during this time.
Lethal levels of insecticides in pollen are an obvious concern, but sublethal levels are also worthy of study as even slight behavioral effects may impact how affected bees carry
out important tasks such as brood rearing, orientation and communication.