HSPH says the study replicated a 2012 finding from the same research group that found a link between low doses of imidacloprid, a type of neonicotinoid insecticide, and Colony Collapse Disorder (CDD) — where bees abandon their hives over the winter and eventually die. It also found low doses of the neonicotinoid insecticide clothianidin had the same negative effect.

The results seem to contradict other findings that suggest CCD may come from bees’ reduced resistance to mites or parasites as a result of exposure to pesticides. The HSPH study found that bees in the hives exhibiting CCD had almost identical levels of pathogen infestation as a group of control hives, most of which survived the winter.

Bayer CropScience says it found the study to be “seriously flawed” and pointed out that feeding honeybees levels of neonicotinoids greater than 10 times what they would normally encounter is unrealistic. Colony failure is to be expected when given the artificially high levels tested over 13 consecutive weeks, the company added.