Mites, warm autumn may be cause of some honeybee disappearances in MN

An additional factor made the mites worse this year, however: a warm fall that has allowed queen bees to keep laying eggs long past when they usually would, Spivak said. If the brood keeps growing after a mite treatment, the mites will keep reproducing too — and the beekeeper might not know it’s happening unless they check. Apiarists should always check after a mite treatment to make sure it has worked, Spivak added.

“We don’t have any way of knowing how many people this is happening to,” Spivak said, because Minnesota has no beekeeper registration or tracking program. The Bee Lab does offer classes for beekeepers, however, and keepers can reach out with questions at the email beelab@umn.edu.

The mite infestations do not qualify as “colony collapse disorder,” a phenomenon first reported in 2006 where hives would similarly disappear, but leave their queens behind. In those situations, bees disappeared in the summer. Scientists still don’t know the exact cause of that situation, Spivak said. Annually, 30% to 40% of U.S. colonies die every winter, mostly from mites and viruses.

The Washington Post recently reported that the number of American honeybee colonies had surged, with the USDA reporting 3.8 million hives nationally in 2022. Much of that growth, however, came from Texas, which has changed its tax code to apply lower property tax rates to land where bees were raised.

Nelson said he and his niece, who tend the bees together, don’t plan to give up their backyard operation. Their original hive is still going strong, and feeding on honey the other bees left behind. They will likely start a new hive next spring, he said.