Insect Repellents and Killer Bees

June 19, 2003

Do Insect Repellents ATTRACT Killer Bees?

Africanized honey bees, better known as "killer bees," are here to stay. These insects can attack with a ferocious punch and they have been blamed for the deaths of several people, dogs, cats and horses. Killer bee attacks can be set off by an animal's smell, breath, motion, color, size, body heat or closeness to a bee colony. Because horses are attacked by killer bees frequently, many horse lovers and veterinarians believe that insect repellents applied to horses may attract killer bees. Some researchers believe that these repellents contain chemical signals that trigger a killer bee attack.

Scientists at the Carl Hayden Bee Research Center (Tucson, AZ) tested the theory that insect repellents attract killer bees. They studied three different repellents:

DEET: a chemical in many insect repellents used by people.

Pyranha: a horse rub that contains citronella, pyrethrins, piperonyl butoxide and other active ingredients.

Repel X: a horse rub that contains pyrethrins, piperonyl butoxide, but no citronella.

The repellents were blown into eight different killer bee colonies. Each test with a repellent also had control test that blew in outside air only. The researchers were careful to hold their breath and move slowly as they attached the blowers to the bee colonies. The number of bee strikes to a target was measured for 110 seconds after the repellents or outside air were blown into a colony.

A Striking Comparison

DEET and Pyranha did not change the behavior of the killer bees: the number of bee strikes after DEET and Pyranha exposure was similar to the number of bee strikes after outside air was used. The number of bee strikes after Repel X exposure, however, was larger than the number of strikes after outside air exposure. Killer bees attacked the target almost twice as often when they were exposed to Repel X compared to when they were exposed to outside air.

It is unclear why Repel X exposure caused the bees to attack. Both Repel X and Pyranha have similar active ingredients. The researchers noticed that Repel X has the odor of "household cleaning agents." Although this odor is not related to the ability of the Repel X to ward off insects, it may be a smell that triggers a killer bee attack.


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