Africanized honey bee (AHB), nicknamed the "killer bee" because of widely publicized incidents of mass stingings in South America, is a threat in the United States to beekeeping and agricultural practices, as well as a fatal threat to people. Since the first detection of a permanent colony in Texas in October 1990, the AHB has established in southern portions of New Mexico, Arizona, and California. While AHB northward movement has slowed dramatically in recent years, the ultimate extent of their range remains uncertain.
AHB are the result of crossbreeding between European and African strains of honey bees by Brazilian geneticists in the 1950s. Bees from Africa were presumably better suited for Brazilian conditions and would be more productive than the European honey bees. However, the bees from Africa were also considerably more aggressive, defending their nests more vigorously and swarming more often, two characteristics that contrast sharply with the more docile European honey bees. AHB were released from the breeding program and spread at remarkable rates. The leading edge advanced up to 300 miles per year through the tropics of South and Central America.
After five years in the United States, AHB have made limited inroads and their northern expansion seems to have slowed dramatically. Factors that may be slowing the spread of AHB include competition and genetic dilution from European bees; reaching northern limits for physiological factors such as cold tolerance or day-length responses; parasitism by Varroa and/or tracheal mites; local geographical barriers such as deserts and mountains; and possibly limited nesting opportunities. Several predictions of the final range of AHB in the United States have been made, ranging from the current situation to extending as far as the mid-latitudes, even surviving as far north as Michigan, Maine, and Canada. However, AHB may be reaching an equilibrium situation where further northern expansion will be seasonal rather than permanent.
Four human deaths have been attributed to AHB in the United States. All have been elderly people receiving multiple stings.
Adapted from an article in California Agriculture (January/February 1997) that appeared in the Kentucky Pest News, March 31, 1997.
This article originally appeared in the April 11, 1997 issue, p. 46.
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