In a "bee treadmill" experiment, the pesticide reduced the length of time and distance that the insects could fly.
Concern has been growing about the effects of agricultural pesticides on the health of bees.
The bees' prevalence of Deformed Wing Virus decreased more than 800-fold.
Only a handful of animals are known to understand the concept.
The new ban adds stricter restrictions to the 2013 decision.
A pesticide manufacturer called the proposed ban "overly conservative" and "extremely impractical."
In the last year, U.S. beekeepers lost more than 40 percent of their hives.
Some don't think it goes far enough.
Scientists don't yet know why more bees are now dying in the summer.