Honeybee colonies are on the rise in the United States, the Department of Agriculture reported Tuesday. The colonies had been declining for years because of parasites and disease. (Joe Raedle/Getty Images)

The number of U.S. honeybee colonies rose in 2017 from a year earlier, according to a U.S. Department of Agriculture survey released Tuesday.

The number of commercial U.S. honeybee colonies rose 3 percent to 2.89 million as of April 1, compared with 2.8 million a year earlier, the department reported. It said the increase was caused by beekeepers adding more bees to make up for previous years’ rapid losses.

Parasites and disease have accounted for the majority of the decline in honeybee population. But another cause of this drop is colony collapse disorder, which has raised concerns among farmers and scientists for a decade.

Colony collapse disorder is a phenomenon in which bees abandon their hives. Beekeepers have improved hive conditions, and the disorder has steadily decreased in recent years.

A possible contributing factor to the changes in the honeybee population has been pesticides. Environmental groups have expressed alarm about the more than the 90 percent decline during the past two decades in the population of pollinators, including wild bees and monarch butterflies. Pesticide manufacturers argue that their products contribute in a very minor way to the population trend.

Tim May, a beekeeper in Harvard, Illinois, and the vice president of the American Beekeeping Federation, says he thinks that it’s difficult to point out specific factors causing the loss of honeybees.

“It’s really tricky,” May said. “Maybe it’s pesticides, maybe it’s not. But when I eliminate everything else, it’s a distinct possibility.”