U.S. beekeepers report losing more than 30 percent of their colonies this past winter.
Tuesday's report by the U.S. Department of Agriculture says the loss is 42 percent higher than the previous winter.
Scientists are struggling to find out exactly what is killing off the world's honeybees. Experts suspect parasites, diseases, genetics, or pesticides, but the exact cause remains elusive.
The European Union has announced it is banning three pesticides that could be responsible.
Bees are essential in pollinating crops and fruit trees. A massive bee die-off could threaten the world's food supply.