- Author: Kathy Keatley Garvey
Although Extension apicuturist emeritus Eric Mussen of the UC Davis Department of Entomology and Nematology, retired in 2014 after 38 years of service, he continues his Extension work.
When a backyard beekeeper's hive in Concord turned aggressive (a swarm killed two dogs, attacked a mail carrier, and stung passsersby), journalists began singling out honey bee guru Eric Mussen and other UC Davis experts for interviews. Apparently, when a beekeeper moved his hive on Friday to make way for landscaping, the bees went on the defensive Friday and Saturday. Most of the bees have since been destroyed.
Some headlines screamed "Killer bees colonizing the Bay Area."
First of all, are they Africanized bees? DNA testing awaits.
“Their BEHAVIOR is very SUGGESTIVE that they could be Africanized,” Mussen told Bug Squad today.
“Until someone runs a definitive test on the on the bees actually involved in the Concord stinging incident, we may never know exactly what genotype the bees were,” Mussen points out, adding that "we have three ways to try to differentiate between Africanized honey bees (AHBs) and European honey bees (EHBs)."
1. Mitochondrial DNA – The California Department of Food and Agricuture (CDFA) still conducts this type of testing once a year to clear the California Bee Breeders for queen exports into Canada. CDFA also uses this criterion as "the one" for declaring Africanization. However, its value in predicting temperament of the colony population is not particularly reliable.
2. Isozymes - the amino acid composition of certain enzymes differs between the two races
3. Morphometrics - computer matching of current sample specimens to verified AHB and EHB samples using measurements of various anatomical features. Hybrids are problematic.
"That type of bee was found around southern California and as far north as not too far from Angles Camp (Calaveras County)," Mussen mentioned. "Further north, they found only specimens with one or two traits, but not all three. That even occurred just into southern Oregon."
“Yes, EHB colonies can behave in that nasty manner, but I think it is more likely that AHBs are involved,” Mussen says. He recalled that twice in the 1980s, swarms of bees from South America accompanied shipments of raw sugar cane into the C&H sugar refinery in Crockett (Contra Costa County).
“We know the first one got away. They think they got the second one, but could not find the queen in either case. Since that time, there have been increasing complaints of "hot" bees from that area, south to Castro Valley (Alameda County).”
Mussen related that “you don't have to have bees that test positive for AHB mitochondria to get extremely defensive behavior. Studies conducted by Dr. Robert Page's lab workers in Mexico (see photo of an Africanized bee below that Page collected) demonstrated the gradual changes in behavior that accompanied increased proportions of AHB semen in A.I. EHB queens":
- 12.5 percent - increased runniness on combs
- 25 percent - add flighty to the list
- 37.5 percent - add significantly more stings to the list
- 50 percent or more - results in full-blown AHB defensive behavior.
“So, if feral AHB colonies exist in the environment, we can have various amounts of ‘mismating' going on and its consequences around the area," Mussen points out,
“Another consideration is that mini-swarms of AHBs sometimes will alight on the outside of an EHB hive and park there for days. The AHB workers slowly integrate themselves into the colony population. Then, when conditions are right, the AHBs kill the EHB queen, the AHB workers and queen march in and take over (usurp the colony).”
“A third possibility is that some novice beekeeper was swayed by advertising for packaged bees from Texas. Advertised as the most gentle stocks, there is no place where mating can be isolated enough to avoid AHB drones.”
Africanized bees are hybrids of a subspecies of bee from southern Africa that was exported to Brazil to improve breeding stock and honey production. Scientists say it escaped and spread throughout South America and into Central America. It expanded into Mexico in 1985, in Texas in 1990, in Arizona in 1993, and in southern California in 1994.
- Author: Kathy Keatley Garvey
Hollywood movie refer to them as "killer bees." Ditto, the news media.
"The known natural distribution of Africanized honey bees (AHB) in California is along a line that runs diagonally from northeastern Tulare County to southwestern San Luis Obispo County, then south to Mexico," says Extension apiculturist Eric Mussen of the UC Davis Department of Entomology. "A colony of AHB was found in Madera County following almond pollination, and the agricultural commissioner decided to call the county colonized instead of participating in a delimiting survey. However, beekeepers in Fresno County are just beginning to report encountering a few more considerably defensive colonies than they used to."
"In southern California, where AHB has been since 1994, they have pretty well filled the basin," Mussen reports. "The last time tests on feral (not human-kept) honey bee colonies and swarms were conducted, AHB were determined to be a little over 80 percent of the totals. That still may be the case with feral bees in that area, although one would expect a bit lessening of defensive behavior over time, as has happened in Brazil."
But, as Mussen points out, "it took 40 years to reach the point that AHB are not too problematic in Brazil. We have had them in California only 18 years."
“There’s no way to tell if honey bees are Africanized without DNA testing,” says Mussen, who writes from the UC Apiaries and Bee Briefs on the UC Davis Department of Entomology website. “They look about the same as the European honey bee. They tend to be a little darker than European honey bees and a little smaller. What sets them apart is their intensive defensive behavior. They’ve been known to chase their victims a quarter of a mile.”
When beekeepers find intensive defensive behavior in their hives, they kill the queen bee and “requeen” the colony. “Over four to six weeks, the original workers die of old age and the new queen replaces them with more daughters,” Mussen said.
Africanized honey bees are the result of attempts to hybridize European honey bees (Apis mellifera) with an African race. Researchers brought Tanzanian queen bees (Apis mellifera scutella) to Brazil in the 1950s. In 1957, some of the African bee descendants escaped from the researchers and beekeepers and began progressing north.
The descendants reached southern Texas in 1990 and southern California in 1994. “In California, they were first found “just outside of Blythe, in Riverside County,” Mussen recalls.
“As an area becomes colonized, the Africanized bees will show their true colors—they will exhibit their intense defensive behavior,” says Mussen, an Extension apiculturist since 1976,
Mussen recommends that anyone working or relaxing in areas known to be colonized by
Africanized bees “take precautions” by avoiding nesting areas. If the bees start to sting, cover your face with a shirt as you run for a building, vehicle or other shelter, he says. You can also carry an Army surplus gnat/mosquito veil with you to protect your face.
The honey bees’ pheromone, resembling the scent of a banana, sounds the alarm, alerting other bees to attack.
Beekeepers who collect swarms in colonized counties have a “high probability” of hiving an Africanized honey bee colony, Mussen points out, and should always look for unacceptable defensive behavior.
His advice: "It still is not a good idea to collect swarms in southern California and hive them in high human population areas."
“Africanized honey bees are not something to be feared,” Mussen said, “but they are to be respected.”
(Note: Click on this USDA map to see where the Africanized bees are now.)