A third of the honeybees in the United States were lost over the last year, part of a decade-long die-off experts said may threaten our food supply. USA Today reports: The annual survey of roughly 5,000 beekeepers showed the 33% dip from April 2016 to April 2017. The decrease is small compared to the survey's previous 10 years, when the decrease hovered at roughly 40%. From 2012 to 2013, nearly half of the nation's colonies died. The death of a colony doesn't necessarily mean a loss of bees, explains vanEngelsdorp, a project director at the Bee Informed Partnership. A beekeeper can salvage a dead colony, but doing so comes at labor and productivity costs. That causes beekeepers to charge farmers more for pollinating crops and creates a scarcity of bees available for pollination. It's a trend that threatens beekeepers trying to make a living and could lead to a drop-off in fruits and nuts reliant on pollination, vanEngelsdor said. So what's killing the honeybees? Parasites, diseases, poor nutrition, and pesticides among many others. The chief killer is the varroa mite, a "lethal parasite," which researchers said spreads among colonies.