Tag Archive for: killer bees northern california

Killer bees in California have quietly gone from a desert curiosity to a fixture of Southern California, and researchers keep finding them farther north. Africanized honey bees crossed the Colorado River in 1994. Today university studies find them across the southern half of the state and into the Central Valley, as far north as Napa and Sacramento. This guide covers their arrival, how far they’ve spread, what that means for Californians, and how to stay safe. It’s part of our Killer Bees 101 guide.

Quick answer: are there killer bees in California?

Yes. Africanized honey bees were first found in California in October 1994 near Blythe in Riverside County. By 1999 they had been found across most of Imperial, San Diego, Riverside, Orange, Los Angeles, and San Bernardino counties, according to UC Riverside. A 2018 UC Davis study found Africanized bees as far north as Napa and Sacramento, and in every county it sampled south of there. In San Diego County, a 2015 study found that about 65% of foraging honey bees carried African mitochondrial DNA.

How killer bees arrived in California

Africanized bees entered the U.S. in South Texas in 1990 and reached Arizona in 1993. California came next.

UC Davis reported in November 1994 that the bees “made their California debut Oct. 24 at the Chuckwalla Valley State Prison, west of Blythe.” (Other UC sources date the swarm’s collection to late October; UC Riverside lists the first discovery as October 1994.) UC Cooperative Extension apiculturist Eric Mussen said at the time that the bees “were an almost pure African genetic strain” and would “almost certainly” move into the Los Angeles Basin.

He was right. A review in the UC journal California Agriculture found that through 1995 only a handful of verified colonies turned up, all in the southeastern corner of the state around Blythe, El Centro, Winterhaven, and Calipatria. After that, the pace picked up. The full national timeline is in The History of Killer Bees.

Where killer bees live in California today

Southern California

UC Riverside reports that during 1999 there were finds “in most areas of Imperial, San Diego, Riverside, Orange, Los Angeles, and San Bernardino Counties, southern Kern County and Ventura County.” In late 2001 foraging bees turned up in Tulare County.

A 2015 study by UC San Diego researchers Yoshiaki Kono and Joshua Kohn, published in PLOS ONE, measured just how Africanized Southern California has become. In San Diego County:

• About 65% of foraging honey bee workers carried African mitochondria.
• About 70% of feral (wild) hives carried the African type, compared with only 13% of managed hives.

In other words, most wild honey bees in San Diego County are now Africanized, while beekeepers’ hives mostly are not.

The Central Valley and Northern California

For years it looked like the bees had stalled. Then a 2018 UC Davis study by Wei Lin and colleagues, also in PLOS ONE, sampled bees across Northern California. It found Africanized honey bees “as far north as Napa and Sacramento” and in “all counties south of these counties.” They were “particularly abundant in parts of the central valley and Monterey.” The authors concluded the bees’ northward spread “may not have stopped” and may still be moving slowly.

That’s a big change from the old idea that Africanized bees would stop near Los Angeles. For context on climate limits, see Where Do Killer Bees Live? and Are Killer Bees Moving North?

Why killer bees matter for California agriculture

California’s farms depend heavily on managed honey bees for pollination, which is one reason researchers watch this spread closely. The 2018 UC Davis study notes that Africanized bees are “highly defensive and somewhat more difficult to manage for commercial purposes than the European honey bees traditionally kept,” and that “many parts of California are strongly agricultural.” The California Agriculture review made a similar point early on: the bees’ impact on the state’s agriculture would depend on how much of California they colonize and on how well beekeepers and cities adapt.

The 2015 San Diego study adds a detail that surprises many people: because so many wild colonies are Africanized, “a large fraction of foraging workers in both urban and rural San Diego County are feral.” The bee on your backyard lemon tree may well come from a wild colony, not a beekeeper’s hive.

Beekeepers are part of the solution. UC Riverside says well-maintained European hives “provide the best defense against AHB, by providing competition, and genetic dilution since new AHB queens may mate with EHB males.” That’s why extension experts encourage responsible beekeeping rather than fear of all honey bees.

How to tell if California bees are Africanized

UC Riverside says Africanized bees “look nearly identical” to the European honey bees California has long had. They can be distinguished only “by measurements under a microscope, and by analysis of their DNA.” The California Department of Food and Agriculture identifies Africanized bees as they enter new areas, but once an area is well colonized, UC Riverside says “it is assumed that all honey bees not under the care of a beekeeper should be treated as Africanized.”

UC Riverside also gives a quick field check: honey bees are about 3/4 inch long, brownish, and a little fuzzy. “Less fuzzy insects with bright yellow and black markings, or with grey paper nests are probably wasps, not bees.” See our guide on how to identify Africanized bees.

Where killer bees nest in California

UC Riverside says Africanized colonies “nest in places European bees did not, including small cavities near the ground like water meter boxes or overturned flower pots.” They swarm more often, too, so colonies are likely to be more common. For a full list of nest sites and warning signs, see Killer Bee Nest: Where Africanized Bees Build.

Deaths from killer bees in California

UC Riverside’s table of U.S. Africanized bee deaths records one in California: an 83-year-old man in Long Beach in September 1999, stung about 50 times. Like most recorded deaths, it involved an older person. The UC review in California Agriculture noted that through 1995, the state had only one stinging incident from an Africanized colony, and it wasn’t fatal.

The risk is real but concentrated. UC Riverside says the danger is greatest for “people allergic to stings, or with limited capacity to escape (the young, old, and handicapped), and to confined livestock or pets.”

How Californians can stay safe

UC Riverside’s advice is short and practical:

• Bee-proof your home. Look for cracks and holes that lead to wall voids. Screen or caulk them, or fill the cavity with insulation. Clean up tires, pots, and other debris.
• Be alert. Look before disturbing vegetation. “Many bees coming and going from a single spot (not just many bees at flowers) may indicate a nest.”
• Get help. Contact trained, equipped bee removal personnel if you find a colony. “Don’t try to remove them alone.”
• If attacked, run for shelter. Get to a car or building and stay there even if some bees follow you in. Don’t jump into water.
• Remove stingers fast. UC Riverside says it doesn’t matter how you remove them, as long as you do it quickly.

Read the full escape plan in What to Do If Killer Bees Attack.

Frequently asked questions

When did killer bees come to California?

October 1994, at Chuckwalla Valley State Prison west of Blythe in Riverside County, according to UC Davis and UC Riverside.

Are there killer bees in Northern California?

Yes. A 2018 UC Davis study found Africanized bees as far north as Napa and Sacramento, and in all sampled counties south of there.

Are there killer bees in Los Angeles and San Diego?

Yes. UC Riverside reported finds across Los Angeles and San Diego counties by 1999. A 2015 study found about 70% of feral hives in San Diego County carried the African type.

Are beekeepers’ hives in California Africanized?

Mostly not. The 2015 San Diego study found the African type in only 13% of managed hives. UC Riverside says well-kept European hives are “the best defense” against Africanized bees.

Who removes killer bees in California?

Trained and equipped bee removal professionals or pest control operators. UC Riverside says not to try removing a colony alone.

Have killer bees reached the San Francisco Bay Area?

Researchers say yes. The 2018 UC Davis study notes that an earlier small-scale study found Africanized honey bees in the Bay Area, “far north of their last recorded distribution,” and its own sampling found them in Bay Area counties including Santa Clara, Contra Costa, and Alameda. They were rare there, though: only about 2% to 4% of the bees sampled in those counties were Africanized, compared with about 28% in Santa Barbara County.

Sources

• UC Riverside Department of Entomology, “Africanized Honeybees”
• UC Davis News, “Africanized Bees L.A.-Bound, May Be Northern Limit” (1994)
• California Agriculture, “Africanized bees, 1990–1995: Initial rapid invasion has slowed in the U.S.”
• Kono Y, Kohn JR (2015), “Range and Frequency of Africanized Honey Bees in California (USA),” PLOS ONE
• Lin W, McBroome J, Rehman M, Johnson BR (2018), “Africanized bees extend their distribution in California,” PLOS ONE