For years, commercial honey bee colonies around the world have reportedly been dying for no apparent reason, but researchers from the University of Illinois may have discovered why. The phenomenon called colony collapse disorder has been reported at commercial bee farms since as early as 2006, and the blame has largely rested with pesticides used to kill mites and other insects. But a new study indicates the true killer might be the high-fructose corn syrup which beekeepers have been feeding their colonies to supplement their honey, the natural staple food taken away from them.

According to a report by Phys.org, commercial honeybee operations began feeding bees high-fructose corn syrups in the 1970s because research then indicated it was safe for the bees. But as new pesticides have come into play as decades passed, the researchers say the bees' immunity response has been compromised. 

The research does not suggest that high-fructose corn syrups are toxic to the bees, but that by eating a an artificial replacement for their natural honey, the bees are not being exposed to other compounds found in naturally in honey that can help bees fight off toxins like the ones in pesticides.

"The widespread apicultural use of honey substitutes, including high-fructose corn syrup, may thus compromise the ability of honey bees to cope with pesticides and pathogens and contribute to colony losses," the researches write in their abstract. They point to the enzyme p-coumaric, which is found in the bees' natural diet that helps strengthen the immune system. 

The study was published in the journal Proceedings of the National Academy of Sciences.