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Discussion Starter · #1 ·
http://ucanr.org/repository/CAO/landingpage.cfm?article=ca.v052n02p9&fulltext=yes

peer-reviewed research article

Blessing or curse? Varroa mite impacts Africanized bee spread and beekeeping

authors

Robert E. Page, Department of Entomology


publication information

California Agriculture 52(2):9-13. DOI: 10.3733/ca.v052n02p9. March-April 1998.

abstract


Africanized honey bees were first detected in California in October 1994. Since then, they have established a foothold in the Imperial Valley and have spread toward San Diego and into Palm Springs. However, their spread has been much slower than originally expected. What has slowed them? The best guess is Varroa jacobsoni, an exotic ectoparasite of honey bees recently introduced into North America. The effects of varroa on Africanized honey bees may be both a blessing and a curse; the latter is especially true if Africanized bees become resistant to varroa and commercial honey bees do not.
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In 1990, before varroa became a serious problem, we conducted a study of the feral honey bee population of California. Samples of bees were collected from 208 feral colonies distributed widely in nest sites throughout the state. We failed to find any colonies infested with varroa (Kraus and Page 1995a). In 1993, we reinspected 124 of the original nest sites and the findings were alarming. Around Sacramento — an area with intensive commercial beekeeping — only 25% of the original nest sites still had colonies of bees living in them. All surviving colonies were infested with varroa. Honey bees nest in enclosed cavities that are usually not easily accessible. However, in some cases the inside of an empty nest was exposed and could be inspected. In every case, dead varroa were found in the bottom of the nest — the smoking gun. The surviving colonies were examined again the following spring (1994). Only one remained and it was heavily infested and unlikely to survive.

Regions of California that had smaller populations of commercial hives in 1993 (as a result of less commercial beekeeping) had reduced levels of infestation of varroa and higher survival in the feral bees. It appears that varroa spread through the feral population aided by the activities of commercial beekeeping. We used estimates of reoccupation rates and rates of survival to estimate life expectancy. Estimations of nest site reoccupation rates following the death of a feral colony and rates of survival resulted in an estimate of the life expectancy of a feral colony before and after the arrival of varroa in areas with intensive commercial beekeeping. Prior to varroa's arrival, the life expectancy was 3.5 years; after varroa arrived the life expectancy was only 6 months to a year. In 3 short years, varroa had reduced the feral population to a tiny fraction of what it had been in 1990. As a consequence of varroa, the feral population of California is greatly reduced to about 15% of its original size in areas with extensive commercial beekeeping. Feral bees are therefore expected to have a greatly reduced effect on the gene pool of the invading AHB. Also, a smaller feral population should result in less competition for invading AHB for food and nest site resources. This is especially true if the AHB are relatively resistant to varroa.
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of the feral colonies in some areas of California.

Resistance to varroa?

For many years, reports have been coming from Brazil that AHB are resistant to varroa. These reports have been confounded with results demonstrating that varroa have a less severe effect on all colonies, even European, in tropical versus temperate climates (Moretto et al. 1991). Resistance, however, is plausible because of the greatly reduced effect that varroa have on their natural host, A. cerana, a close relative of our western honey bee. Recent evidence from Brazilian researchers suggests that, like A. cerana, Brazilian AHB have the ability to detect varroa on the bodies of adult workers and remove them (Moretto et al. 1993). This may provide a mechanism for resistance. Varroa were introduced into southern Brazil in 1972, after the spread of AHB, so the proposed resistance may have been selected in Brazil and may not be a characteristic of the spreading population of AHB. Or, AHB may be “preadapted” to be more resistant to varroa than are bees of European origins. The AHB population spreading into California did not encounter varroa until after it had invaded Mexico and Texas.


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"Recent evidence from Brazilian researchers suggests that, like A. cerana, Brazilian AHB have the ability to detect varroa on the bodies of adult workers and remove them (Moretto et al. 1993)"

That's interesting Bees4u.

The reason mites walk around unmolested on honeybees in a hive, is chemical camouflage, ie, they smell the same as the bees. So the other bees around the bee with the mite on it, don't know there is anything there that shouldn't be.

It could be (just a theory), that AHB or at least some of them, smell a bit different to EHB. If that is the case, the AHB would detect the different smell of varroa and deal to them.
 

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Interesting article; however, I keep hearing that A. cerana are able to resist varroa. And yet I have looked for them in recent travels to Japan, Korea, and Vietnam, and my observation is that there are very few bees there.

And as far as varroa not being devastating in the tropics, I can assure you that they have caused severe losses here in tropical Hawaii.
 

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Discussion Starter · #5 ·
http://www.slideshare.net/PaulMcCarty/beekeeping-with-nm-feral-bees-v2

I wish Paul would weight in on this.

He removes ferals. He hives them. He's treatment free.

He is just so well informed on what is going on in New Mexico.

Why pick California? With almond pollination, it's the epicenter of our problems.
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California is not the epicenter. Check out the history of Varroa being found in Florida and how it was found in many states later.
It is not about picking California. It's about what happened to the feral colonies.

Feral colonies in Tucscon Az were also lost to Varroa
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After the above report was written, it was discovered that the strain of varroa in Brazil is different than what we have here in the USA. The varroa here is the Korean strain which is more damaging than that in Brazil.
 

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Heard my name invoked - yes I see bees like this a lot and yes they are mite resistant. I maintain feral colonies for a short while after removal to determine their temperament, then requeen if needed. Some of these bees have differing degrees of African blood. They are definitely mite resistant. I have even seen them chewing mites from each other. Now, as far as it being a Brazilian/AHB thing or just a developing feral trait, I am not certain. Nor am I 100% convinced that the feral bees we see in my region are totally Brazilian in nature. My personal feeling is that the Brazilians are not the majority, except for in the southern desert lowlands, though they are an influence. Our highland bees don't seem to be influenced by the Brazilians, yet they have survived mites. I think they have some African influence, but it may not be Brazilian. Go up a bit further north (albuquerqe) and the ferals are mostly domestic escapees.

I have been told there was a period here where there were no feral bees shortly after the mites arrived. That tells me something is happening that helps them survive and even prosper in most cases. Now, if it is only an African trait or if it has spilled over into other feral bees, I don't know. I do know that the African type bees are much more sensitive to smells. Don't ever breathe on a frame of them!
 
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