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HomeBeeKeepingOrganic management with Varroa - The Apiarist

Organic management with Varroa – The Apiarist

Synopsis : Honey bees have been eradicated on Santa Cruz Island following the introduction of Varroa. This offers some helpful classes for beekeepers on the significance of controlling Varroa.


Honey bees aren’t native to North America. They have been first launched in March 1622 at Jamestown, Virginia. The bees did nicely and unfold west, following the settlers. They lastly arrived on the west coast, in Santa Clara, California, 231 years later in 1853. Of a dozen hives ordered by Christopher Shelton, a Santa Clara botanist and rancher, just one survived the journey from New York by way of Panama.

Shelton barely had an opportunity to get pleasure from his bees as he was sadly killed when the steamboat Jenny Lind exploded in mid-April 1853.

Explosion on the steamboat Jenny Lind close to San Francisco, California

His bees survived and three hives derived from the unique inventory have been auctioned for $110 every. This was over 20 occasions the worth of hives on the east coast at the moment and equal to over $4200 right this moment .

Californian Channel Islands map

Bees have been in demand they usually continued to unfold – each as feral swarms and as farmers established apiaries to assist pollination and for honey manufacturing. Having reached the California coast they have been then unfold to the close by islands. Bees have been transported to Santa Cruz, the biggest of the eight Channel Islands close to Los Angeles, within the 1880’s. They flourished, however didn’t unfold to the opposite Channel Islands.

Discipline station, nature reserves, pigs and bees

Santa Cruz Island is 250 sq. kilometres in space and lies ~35 km south of Santa Barbara. It is among the 4 Northern Channel islands. There’s a lengthy central valley mendacity roughly east-west and the rocky mountainous land reaches 740 m. It has a marine temperate local weather; the typical high and low temperatures are 9°C and 21°C respectively and it receives about 0.5 m of rain a yr. It’s a good surroundings for bees.

From the 1880’s to 1960’s Santa Cruz Island was farmed – primarily for wine and wool, and from the 1940’s for cattle – however, after interval of college geology subject journeys and the institution of a subject station on the island, in 1973 it turned a part of the College of California’s Pure Reserve System (UC NRS).

Within the late 1970’s the Stanton household offered their ranching enterprise on the island to The Nature Conservancy who subsequently purchased extra land on the japanese finish of the island.

Santa Cruz Island is now collectively owned by The Nature Conservancy, Nationwide Parks Service, UC NRS and the Santa Cruz Island Basis and far of the island is used for scientific analysis and training.

However what in regards to the bees?

Good query.

As a nature reserve and analysis station, the presence of non-native species causes a possible drawback. Why go to all of the expense of managing a distant island analysis centre if all the identical species are current as on the mainland?

The Nature Conservancy due to this fact initiated a programme of eradicating non-native species. It took 14 months to remove the feral pigs, utilizing a mix of trapping, helicopter-based capturing and the discharge of sterilised radio-tagged pigs to find the stragglers .

However eliminating the bees took a bit longer …

Save the bees, or not

Why eliminate the bees? Certainly they weren’t doing any hurt?

The introduction of any non-native species upsets the steadiness (if there’s ever steadiness) within the ecosystem. The launched species competes straight or not directly with these native to the world and may result in native extinctions.

Jonathan Rosen has described how honey bee swarms, by occupying tree cavities beforehand used for nesting, most likely performed a serious position within the extinction of the Carolina parakeet.

Pining for the fjords … a stuffed Carolina parakeet (nailed to its perch)

Competitors between honey bees and native pollinators has been nicely studied. It isn’t all the time detrimental, but it surely actually could be. Moreover, it’s most likely extra prone to be detrimental in a small, remoted, island ecosystem. For instance, research confirmed that the presence of honey bees dramatically lowered visitation of native pollinator to manzanita blossoms on Santa Cruz Island.

As a part of the bigger programme of non-native plant and animal eradication on Santa Cruz Island plans have been drawn up within the late 1980’s to remove European honey bees. The anticipated advantages have been to:

  • remove competitors with native bee species (and presumably different non-bee pollinators, although these hardly ever get a point out 🙁 )
  • scale back pollination of weed species (a few of which have been additionally non-native to Santa Cruz Island)
  • facilitate restoration of native plant species that have been reliant on native bee pollination
  • present a ‘subject laboratory’ free from ‘unique’ honey bees through which comparative research of native pollinators can be attainable

Killer bees

After the plans to eradicate Apis mellifera have been authorized an extra potential profit turned obvious.

There have been rising issues in regards to the unfold of Africanised honey bees which had lately reached Santa Barbara County. Though there was fairly compelling proof that swarms couldn’t cross from the mainland (e.g. not one of the different Northern Channel Islands had been colonised by bees) there have been issues that the Santa Ana winds may assist blow drones from the mainland.

Had these drones arrived they could mate with the non-native however however native queens ensuing within the unfold of the dominant genes for defensiveness and absconding. The ensuing swarmy, aggressive Africanised bees would trigger issues for guests and scientists engaged on the island (as they’ve for guests to Joshua Tree Nationwide Park).

Aerial view of Santa Cruz Island

Though the introgression of African honey bee genes was used as additional justification for the eradication it’s not clear whether or not drones may truly cross 30-40 km of open sea .

As an apart, there’s a present undertaking – the amusingly named Sport of Drones – working on the Isles of Scilly investigating whether or not drones can cross the ocean between St Agnes, Tresco, Bryher, St Mary’s and St Martin’s. These are, at most, 11 km aside (northern most tip of St Martin’s to most southerly level of St Agnes) however the person islands are solely separated by 1-2 km. I might be stunned if drones couldn’t cross that distance (at the very least with a powerful following wind).

Killing bees

Adrian Wenner and colleagues set about exterminating the honey bees on Santa Cruz Island (Wenner et al., 2009). The method began in 1988 and led to 2007, and was divided into 4 phases:

  1. 1988-1993 – location and elimination of feral colonies
  2. 1994-1997 – organic management and colony demise
  3. 1998-2004 – monitoring residual honey bee exercise
  4. 2005-2007 – affirmation of the absence of honey bees

None of that is ’beekeeping’ – truly it’s the precise reverse – so I don’t intend to dwell in a lot element on the work that was performed. Nonetheless, the ’94-’97 part consists of some sobering classes for beekeepers that are value discussing.

By the tip of part 1 the crew had recognized the existence (if not the situation) of at the very least 200 colonies and eradicated 153 of them.

Keep in mind, none of those have been managed colonies in hives. They have been all feral colonies occupying pure cavities in bushes or rocks and so on. Every colony was discovered utilizing painstaking bee lining strategies much like these described in Thomas Seeley’s e book Following the Wild Bees.

As soon as situated, nests have been destroyed with methyl chloroform and the cavity sealed to stop it being reoccupied.

Some colonies couldn’t be accessed; in these circumstances acephate-laced sucrose-honey syrup baits have been used. This organophosphate has delayed toxicity for bees, permitting foragers to return to the colony which sooner or later dies. This strategy had been partially profitable in eliminating Africanised bees on the mainland (Williams et al., 1989), however baits wanted to be be monitored to keep away from killing the opposite bugs they attracted.

The scientists additionally deployed swarm traps (aka bait hives) and destroyed any swarms that moved in.

Collectively these interventions lowered honey bee numbers considerably – as monitored by common observations at pollen- or nectar-rich crops – however didn’t eradicate them.

Let there be mite

Heavy rains in January ’93 washed out roads on Santa Cruz Island, thereby severely limiting journey across the island. As well as, the earlier removing of cattle had resulted within the near-uncontrolled progress of fennel which now shaped dense, impenetrable thickets.

Bee lining turned unattainable and the scientists needed to invent extra devious methods to remove the residual feral colonies.

The strategy they selected concerned the introduction of Varroa.

Varroa was first detected within the USA in 1987 (in Florida) and have become widespread over the subsequent 5-8 years. Up till 1994 the honey bees on Santa Cruz Island have been freed from the ectoparasitic mite.

It was probably that they might have remained that manner … there was no beekeeping on Santa Cruz Island and the situation was too distant for bees to cross from the mainland (see above).

Varroa was already recognized to have a devastating affect on the well being of honey bee colonies (Kraus and Web page, 1995). It was additionally recognized that, aside from its native host Apis cerana (the Japanese honey bee), Varroa didn’t parasitise different bee or wasp species (Kevan et al., 1991).

These two details – host specificity and injury inflicted – instructed that Varroa could possibly be used for organic management (‘biocontrol’) on Santa Cruz Island.

Organic management

Organic management or biocontrol is a technique of controlling pests utilizing pure mechanisms corresponding to predation or parasitism.

The pest could possibly be any residing factor – from animals to bacterial plant illnesses – current the place it’s undesirable.

On Santa Cruz Island the pest was the honey bee.

In different research (coated in a earlier submit entitled Extra from the fungi ) biocontrol of Varroa has been investigated.

Management of the pest entails the introduction or utility of a organic management agent. The important thing necessities of the latter have already been highlighted – specificity and injury.

Organic management works nicely when the specificity is excessive and the injury is due to this fact tightly focused. It may be an abject failure – or worse, it will probably injury the ecosystem – if the specificity is low and/or the injury is widespread.

The cane toad was launched to Australia to regulate infestations of buck cane beetle (a pest of sugar cane). Cane toads have been launched in 1935 and quickly unfold. Sadly, cane toads can’t bounce very excessive and so singularly failed to regulate the buck cane beetle which tends to keep excessive up the cane stems.

Feminine cane toad (not leaping)

Nevertheless it will get worse; cane toads have a really catholic weight-reduction plan and so outcompeted different amphibians. They launched international illnesses to the native frogs and toads and – due to the poisons secreted from their pores and skin – harmed or killed predators that tried to eat them.


Vertebrates are often poor organic management brokers as they are typically generalist feeders i.e. no specificity.

However Varroa is particular and so the injury it causes is targeted. The probability of ecosystem injury was thought of low and so the mite was launched to the island.

Introduction of Varroa

In late 1993 Adrian Wenner caught 85 foraging bees and, to every one, added a single Varroa mite. The bees have been then launched and presumably flew again to their colonies … taking the hitchhiking mite with them.

Grownup mites – the darkish crimson ones you see littering the Varroa tray after you deal with with Apivar – are mated females.

As a consequence of their incestuous life-style a single mite is enough to provoke a brand new infestation.

The mated grownup feminine mite parasitises a honey bee pupa and produces a sequence of younger; the primary is male, the rest are feminine. You’re most likely studying this earlier than the 9 pm watershed so I’ll depart it to your lurid creativeness to work out what occurs subsequent (or you’ll be able to learn all of the sordid particulars in Know your enemy).

The presence of honey bees – decided by profitable swarm trapping or subject statement at probably websites – was then usually monitored over the subsequent 4 years.

Swarm numbers remained largely unchanged till 1996 after which dramatically decreased.

Numbers of recent swarms on Santa Cruz Island 1991 – 2005. Varroa introduction indicated.

It’s value noting that in ’94-’96 over 70 swarms have been present in pure websites or bait hives. There will need to have been a big variety of established colonies in 1993 to provide this variety of swarms.

However, from 1997 all of it stopped … solely a single swarm was subsequently discovered, in a pure cavity in 2002.

Monitoring and affirmation of eradication

From 1998 to 2004 the scientists continued to actively monitor the island for honey bees, specializing in 19 areas wealthy in pure forage. Though honey bees have been discovered – in lowering numbers – there have been too few to aim bee lining to find their colonies.

On the websites being monitored, bees have been detected 9, 7, 4, 2 and 1 occasions respectively within the 5 years from 2000 to 2004. After that, regardless of continued monitoring, no extra honey bees have been detected.

The ultimate part of the undertaking (’05-’07) confirmed the absence of honey bees on Santa Cruz Island.

While, as a scientist, I’m a agency believer that ’absence of proof doesn’t imply proof of absence’, as a beekeeper I’m nicely conscious that if there aren’t any scout bees, no swarms and no foragers (after I search in probably locations) then there aren’t any honey bee colonies.

Classes for beekeepers

I wouldn’t have recounted this sorry story – at the very least from a beekeeping perspective – except I believed there have been some helpful classes for beekeepers.

There are (at the very least) three.

The primary pertains to Varroa resistance, the second to Varroa transmission within the surroundings and the final to ‘protected’ ranges of Varroa. All require some ‘arm waving guesstimates’ , however have grounding in different scientific research.

Varroa resistance

There wasn’t any.

At a really conservative estimate there have been at the very least 20 colonies remaining on Santa Cruz Island in 1995. I say ‘conservative’ as a result of that assumes every colony generated two swarms that season (see graph above). In research of different pure colonies solely about 75% swarm yearly, which means the precise variety of colonies may have been over 50.

The numbers – 20 or 50 – matter as they’re each a lot greater than the variety of colonies most beekeepers handle (which, primarily based upon BBKA quoted statistics, is about 5).

Whether or not it was 20 or 50, they have been all eradicated following the introduction of 85 mites. Colonies didn’t turn into proof against Varroa.

This all took a couple of years, however – inferring from the swarm numbers above – the overwhelming majority of colonies have been killed in simply two years, 1994 and 1995. This timing would match with quite a few different research of colony demise because of mites.

Wenner estimates that solely 3 colonies survived till 2001.

Leaving small numbers of colonies untreated with an expectation that resistance – and even tolerance (which is each extra probably and never essentially useful) – will come up is a futile train.

I’ve mentioned this earlier than … it’s a numbers sport, and a handful of colonies isn’t sufficient.

Varroa unfold

Wenner doesn’t elaborate on the place the foragers have been captured earlier than he added the mites. If I used to be going to aim this I’d have chosen a number of websites across the island to make sure as many feral colonies as attainable acquired mites … allow us to assume that’s what he did.

Nonetheless, with 85 mites piggybacking on returning employees, and someplace between (my guesstimated) 20 to 50 colonies, I feel it’s extremely probably that at the very least some colonies acquired none of this ’founding’ mite inhabitants.

But virtually all of the colonies died inside two years, and people who didn’t subsequently died with no additional intervention from the scientists. We don’t know what killed off the final surviving colonies however — and I do know I’m sticking my neck out right here – I guess it was the mites.

That is compelling proof for the unfold of Varroa all through the island surroundings, a course of that happens because of the actions of drifting and robbing.

If a neighbouring apiary to yours has mites some will find yourself in your hives … except you’re separated by a number of kilometres .

The transmission of mites within the surroundings is an excellent motive to follow coordinated Varroa management.

One mite is all it takes

However, simply as I’ve argued that some colonies could have acquired none of the founding mites, I’m equally positive that others may have acquired very small numbers of mites, maybe only one.

And one mite is all it takes.

With out distinctive beekeeping expertise, resistance within the bee inhabitants or rational Varroa management there isn’t any protected stage of mites in a colony.

The extra you forestall mites getting into the colony within the first place, and the extra of these which are current you eradicate, the higher it’s in your bees.

Right here endeth the lesson 😉

Be aware

It’s value noting that island populations do provide alternatives for the event of Varroa resistant (or tolerant) traits … when you begin with sufficient colonies. Fries et al., (2006) describes the traits of the 13 surviving colonies on Gotland after leaving about 180 colonies untreated for a number of years. I’ve talked about this beforehand and can return to it once more to cowl some associated current research.


Fries, I., Imdorf, A. and Rosenkranz, P. (2006) ‘Survival of mite infested (Varroa destructor) honey bee (Apis mellifera) colonies in a Nordic local weather’, Apidologie, 37(5), pp. 564–570. Accessible at:

Kevan, P.G., Laverty, T.M. and Denmark, H.A. (1990) ‘Affiliation of Varroa Jacobsoni with Organisms aside from Honeybees and Implications for its Dispersal’, Bee World, 71(3), pp. 119–121. Accessible at:

Kraus, B. and Web page, R.E. (1995) ‘Impact of Varroa jacobsoni (Mesostigmata: Varroidae) on feral Apis mellifera (Hymenoptera: Apidae) in California’, Environmental Entomology, 24(6), pp. 1473–1480. Accessible at:

Wenner, A.M., Thorp, R.W., and Barthell, J.F. (2009) ‘Organic management and eradication of feral honey bee colonies on Santa Cruz Island, California: A abstract’, Proceedings of the seventh California Islands Symposium, pp. 327–335. Accessible as a PDF.

Williams, J.L., Danka, R.G. and Rinderer, T.E. (1989) ‘Baiting system for selective abatement of undesirable honey bees’, Apidologie, 20(2), pp. 175–179. Accessible at:




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