Beekeeper Charles Smith of Fellsmere said he found mounds of dead bees spilling out of his 400 hives Monday and that another beekeeper maintaining hives about 1 mile away reported a similar amount of dead bees, Florida Today reported.
"This is a total wipeout," said Smith, who estimates he lost $150,000 in honey proceeds, the bees and their future generations.
Brevard County officials said they don't think recent mosquito control spraying in the area killed the bees.
But die-off left had all the hallmarks of a pesticide kill, experts said.
"Right now it's too early to start pointing fingers at anybody," University of Florida entomologist Bill Kern said.
"The fact that it was so widespread and so rapid, I think you can pretty much rule out disease," he said.
"It happened essentially almost in one day. Usually diseases affect adults or the brood; you don't have something that kills them both."
State agriculture officials collected dead and dying bees from both hives to test for pesticides, which could take several weeks.
"Right now, we don't know what pesticide, if any, was involved," Kern said. "If there's a real high level, it's going to be pretty obvious."