Published on 05/09/00

Beekeepers Fighting Pests with 'Silver Bullet'

A pesticide used to kill varroa mites in Georgia bee hives is also proving effective in killing small hive beetles.

Varroa mites and small hive beetles are major pests to bees and their keepers in Georgia. In late January, Georgia Commissioner of Agriculture Tommy Irvin granted a temporary clearance for beekeepers to use coumaphos, a pesticide, to fight them. However, beekeepers must remove honey from the combs of coumaphos-treated hives.

Important for Growing Crops

"Varroa mites and small hive beetles are causing our honey bee population to dwindle," Irvin said. "Honeybees play an important role in pollinating many fruits and vegetables and are responsible for pollinating plants that account for approximately one-third of the food we eat."

The small hive beetle is a new pest, but varroa mites have been around for years.

"We've been fighting varroa mites since 1987," said Keith Delaplane, an Extension Service entomologist with the University of Georgia College of Agricultural and Environmental Sciences. "The recent problem is their resistance to the old stand-by product we were using."

Delaplane said the new pesticide is being used for two reasons. "One is because the varroa mites have become resistant to the current pesticide, apistan," he said. "The other is to fight a new pest, the small hive beetle."

Came to the U.S. in 1998

The small hive beetle was unknown in the United States until its unexpected arrival in 1998. "That year," Delaplane said, "we found it in Georgia and in Florida."

Both pests are harmful to bees and to beekeepers' wallets.

"The varroa mite is like a tick," Delaplane said. "It attaches to the outside of the bee and actually pierces into it. It's broadly dispersed across the state and is causing colonies to die all over Georgia."

The small hive beetle, on the other hand, is much less widely distributed, with concentrations in south Georgia and several counties in metro Atlanta.

"It's a hive scavenger," Delaplane said. "The larvae are carnivorous and eat immature bees."

Hurt the Bees and Eat the Honey

They also eat honey. "They go tunneling through the combs and make a mess of everything," he said. "Colonies that are severely infested will abandon the nests, and the beekeeper comes back to find an empty box."

Delaplane said the beetles can linger in colonies for weeks before causing damage. "When conditions are right, the larvae explode, and the colony comes crashing down," he said.

U.S. Department of Agriculture scientists had been looking for products to control varroa mites, anticipating the day the current control product would stop working, he said.

A 'Silver Bullet' for Both Pests

"One of them, coumaphos, looked promising," Delaplane said. "When the small hive beetle showed up, they decided to try coumaphos on them, too. And it worked. So fortunately we got a silver bullet, so to speak, that works for both of our problems at once: the resistant mites and the beetles."

Georgia has 75,000 bee colonies and 2,000 hobby and commercial beekeepers. The industry generates $70 million each year in the state through sales of honey, beeswax, queen bees and package bees.

"Georgia ranks 14th in the nation in honey production and second, behind California, in queen bee and packaged bee production," Delaplane said. "These are bees that are shipped all to beekeepers over the world for starting up colonies and for crop pollination. We dominate on the east coast as a supplier of bees."

Searching for Nonchemical Controls

Delaplane is doing his part to fight these pests. "My research focuses on alternative controls that are less chemically intense," he said.

Last summer, he tested a hive screen that controls the varroa mites. "The screen creates a false floor in the bee hive," he said. "When the mites fall through the screen, they have trouble climbing back onto the bees."

The screens were developed in France. Georgia beekeepers are now using them.

Sharon Omahen is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.