Honeybees are social insects. Their colony only survives as a community, and healthy new generations are very important. It is therefore not surprising that honeybees invest significant care and resources into their offspring: nurse bees feed the young larvae with a food juice made from nectar and pollen which they produce in a gland in their head.

However, pollen, in particular, can contain residues of various insecticides and other pesticides. It is therefore very likely that bee larvae are exposed to a complex mixture of chemicals.

Read more here: Pesticides in combination can have unexpected effects on the development of honeybees (msn.com)

And here:  The neonicotinoid acetamiprid reduces larval and adult survival in honeybees (Apis mellifera) and interacts with a fungicide mixture - ScienceDirect