Biologists at the University of California San Diego studied how honey bees fared with exposure to neonicotinoids along with limited nutrient sources. Honey bees used in the study serve as bioindicators of environmental health. The researchers were surprised to find that bee deaths increased by up to 50% more than they expected compared with the individual effects of pesticides and poor nutrition. This was the first study to test such "synergistic" effects when these threats are combined and amplified beyond the sums of the individual factors. "These findings should cause us to rethink our current pesticide risk assessment procedures, which, based upon our findings, may underestimate the toxic effects of pesticides on bees," said study co-author Simone Tosi.