Researchers from the Harvard School of Public Health write that new research provides "convincing evidence" of the link between imidacloprid and the phenomenon known as Colony Collapse Disorder. Lead author of the study, Chensheng (Alex) Lu, stated that experiments showed a dose of 20 parts per billion of imidacloprid (less than the concentrations bees would encounter while foraging in sprayed crops), was enough to lead to Colony Collapse Disorder in 94% of colonies within 23 weeks. The hives were nearly empty and the researchers did not find signs of the "Nosema" fungus or "Varroa" mites. The researchers proposed two possible sources of bees' exposure to imidacloprid. The first is through the nectar of plants sprayed with the pesticide itself, which is predicted by researchers at the University of Stirling, U.K., to have widespread impacts as imidacloprid is registered for use on over 140 crops in at least 120 countries. The second is through the high-fructose corn-syrup that most bee-keepers in the United States use to feed their bees. Since application of imidacloprid to corn in the United States began in 2005 cases of Colony Collapse Disorder have grown significantly: from losses of 17% to 20% throughout the 1990s to somewhere between 30% and 90% of colonies in the United States since 2006.