- 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
Africanized honey bees arrived in southern California in 1994 and are expanding north. How far north are they now?
That's the question being asked all over Central and Northern California, especially since "The Concord Incident" or what happened along Hitchcock Road, Concord last Friday and Saturday. Apparently a backyard beekeeper was trying to move two hives on Friday to allow his father to do some landscaping. The beekeeper reportedly moved the first hive successfully, but when he tried to move the second hive, the bees became highly defensive and wreaked havoc. They killed two dogs, attacked a mail carrier, and stung a number of passersby.
Were they Africanized bees? DNA tests will determine that.
Meanwhile, what is the northern boundary for Africanized bees?
Extension apiculturist (emeritus) Eric Mussen, who retired in June 2014 after 38 years of service, explained it this way:
"The northern boundary of AHBs depends upon the criteria you use to analyze an individual:
1. Mitochondrial DNA: Used by California Department of Food and Agriculture (CDFA) to call them Africanized
2. Morphometrics: Measure quite a number of anatomical features and compare them to features of EHBs and AHBs. Hybrids are hard to categorize, thus not used by CDFA, but the USDA likes it (they "invented" it)
3. Isozymes: Enzymes from AHBs and EHBs have different amino acid arrangements
There are "pockets of bees having one or two of the three criteria, but bees with all three criteria haven't been demonstrated more than about half way up the state from the southern end," Musssen said. Africanized honeybees or AHBs from San Diego, etc., have all three criteria."
And the farthest north they've been found? "If I remember correctly, Angels Camp (Calaveras County) vicinity was farthest north find of samples with all three criteria positive," Mussen related. "Samples around the Concord area had two criteria (up to now). Two samples from very southern Oregon had one criterion."
UC San Diego scientists reported in a press release issued Sept. 11, 2015 that "Africanized bees continue to spread in California."
The study, published that week in the journal PLOS One, "found that more than 60 percent of the foraging honey bees in San Diego County are Africanized and that Africanized bees can now be found as far north as California's delta region," wrote news communicator Kim McDonald.
Said biologist Joshua Kohn, a biology professor who headed the study: "“Our study shows that the large majority of bees one encounters in San Diego County are Africanized and that most of the bees you encounter are from feral colonies, not managed hives,” said Joshua Kohn, a professor of biology at UC San Diego who headed the study."
McDonald explained that "Africanized bees are hybrids of a subspecies from southern Africa that were brought to Brazil to improve bee breeding stock and honey production, but escaped and spread throughout South America and Central America, arriving in Mexico in 1985 and Texas in 1990. Their aggressive behavior and tendency to swarm victims have led them to be dubbed 'killer bees.'"
Kohn and his graduate student Yoshiaki Kono "found Africanized genetic traits in honey bees as far north as 40 kilometers south of Sacramento in the state's central valley," McDonald wrote. "In the bees they collected in San Diego, they also discovered that more than 60 percent of foraging honey bee workers have Africanized genetic traits, but that African traits are found in only 13 percent of managed or commercial hives."
The scientists said the Africanized bees' northward expansion has slowed considerable, and that these bees have a limited ability to survive cold temperatures. In other words, they cannot survive cold winters. However, their presence may "improve the genetic stock of honey bees used in agriculture," according to Kohn.
At UC Davis, assistant professor Brian Johnson of the Department of Entomology and Nematology, is doing research on genetic dispersion of AHBs around the state. He has collected and frozen a large number of feral bee samples from around the south and central portions of the state.
After what happened last weekend, interest in AHB expansion has definitely accelerated. Stay tuned.