Mosquito control-related bee kills are avoidable

(09/02/16) BATON ROUGE, La – Good communication between mosquito control operators and beekeepers and proper mosquito control techniques can prevent massive bee kills like the one that occurred earlier this week in South Carolina, according to an LSU AgCenter researcher.

Entomologist Kristen Healy has conducted extensive research evaluating the effects of pesticides on honeybees and has determined that when done properly, mosquito control has minimal effects on honeybee health.

With proper notification from mosquito control programs, beekeepers can do things to minimize the effects of pesticides, Healy said.

“They can request to be part of a no-spray zone, or they can cover their hives with tarps during spraying,” Healy said.

She emphasized the need for good communication between the two groups, adding that it seems not all beekeepers in Dorchester County, where the acute killing occurred, received notification of aerial spraying near their hives.

The aerial spraying in Dorchester County likely occurred in the morning after sunrise, which Healy said is not typical.

“According to the label instructions, you are supposed to time applications either two hours after sunset or two hours before sunrise,” she said. “Bee kills can happen when you spray too early before sunset or too late after sunrise when bees are more active.”

In her study, Healy conducted field trials using sentinel beehives in areas that received frequent applications of mosquito control pesticides and in areas that received no applications. During the study, the mosquito control program used both truck-based applications of pyrethroids and aerial applications of Naled, the insecticide used in Dorchester Country.

The researchers counted average numbers of dead bees at all hives and did not see any increased mortality because of mosquito control activities, Healy said. Researchers also measured stress by analyzing indicator enzymes from the field-test bees and found no difference in stress between the two groups.

Bee behavior could be another factor in the South Carolina bee kill, Healy said. When temperatures are high, bees may “beard,” leaving the hive and clustering outside to help ventilate it.

“According to the articles in the newspaper, many of the dead bees were found in front of the hives,” she said. This is a good indication that bees were probably bearding and were the most likely ones exposed to the pesticide.

Beekeepers can do several things to help minimize exposure to pesticides sprayed during evening hours, Healy said. They should communicate with mosquito control, and if an application will occur near their hives, beekeepers can minimize exposure during spray events in hot weather by ventilating hives by creating holes and spaces and using screens to increase airflow to reduce bearding or by covering hives with tarps.

Beekeepers should report any acute kills immediately to determine the cause. In most cases, healthy colonies can recover from acute kills of bearding bees, Healy said.

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Vivek Pokhrel, a master’s degree student working with LSU AgCenter entomologist Kristen Healy, tends to bees at the USDA Honey Bee Breeding, Genetics and Physiology Research facility in Baton Rouge, Louisiana, on July 22, 2016. Photo by Olivia McClure/LSU AgCenter

9/2/2016 9:10:03 PM
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