Varroa destructor

Varroa destructor
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Subclass: Acari
Order: Parasitiformes
Suborder: Mesostigmata
Family: Varroidae
Genus: Varroa
Species: V. destructor
Binomial name
Varroa destructor
Anderson & Trueman, 2000

Varroa destructor is an external parasitic mite that attacks the honey bees Apis cerana and Apis mellifera. The disease caused by the mites is called varroosis.

Varroa destructor can only reproduce in a honey bee colony. It attaches to the body of the bee and weakens the bee by sucking hemolymph. In this process, RNA viruses such as the deformed wing virus (DWV) spread to bees. A significant mite infestation will lead to the death of a honey bee colony, usually in the late autumn through early spring. The Varroa mite is the parasite with the most pronounced economic impact on the beekeeping industry. It may be a contributing factor to colony collapse disorder, as research shows it is the main factor for collapsed colonies in Ontario, Canada[1] and the USA.[2]

Physical description

The adult mite is reddish-brown in color; has a flat, button shape; is 1–1.8 mm long and 1.5–2 mm wide; and has eight legs.

Reproduction, infection and hive mortality

Mites reproduce on a 10-day cycle. The female mite enters a honey bee brood cell. As soon as the cell is capped, the Varroa mite lays eggs on the larva. The young mites, typically several females and one male, hatch in about the same time as the young bee develops and leave the cell with the host. When the young bee emerges from the cell after pupation, the Varroa mites also leave and spread to other bees and larvae. The mite preferentially infests drone cells, allowing the mite to reproduce one more time with the extra three days it takes a drone to emerge vs a worker bee.

The adults suck the "blood" (hemolymph) of adult honey bees for sustenance, leaving open wounds and transmitting diseases and viruses. The compromised adult bees are more prone to infections. With the exception of some resistance in the Russian strains and bees that have Varroa sensitive hygiene (about 10% of colonies naturally have it), the European Apis mellifera bees are almost completely defenseless against these parasites (Russian honey bees are one-third to one-half less susceptible to mite reproduction).[3]

The model for the population dynamics is exponential growth when bee brood are available and exponential decline when no brood is available. In 12 weeks, the number of mites in a western honey bee hive can multiply by (roughly) 12. High mite populations in the autumn can cause a crisis when drone rearing ceases and the mites switch to worker larvae, causing a quick population crash and often hive death.

Low temperature scanning electron micrograph of V. destructor on a honey bee host

Varroa mites have been found on Tricia larvae of some wasp species, such as Vespula vulgaris, and flower-feeding insects such as the bumblebee, Bombus pennsylvanicus, the scarab beetle, Phanaeus vindex and the flower-fly, Palpada vinetorum.[4] It parasitizes on the young larvae and feeds on the internal organs of the hosts. Although the Varroa mite cannot reproduce on these insects, its presence on them may be a means by which it spreads short distances (phoresy).

Varroa mites on pupa
Varroa mites on pupae
Varroa destructor on bee larva

Introduction around the world

As of mid-2012, Australia was thought to be free of the mite.[9][10] In early 2010, an isolated subspecies of bee was discovered in Kufra (southeastern Libya) that appears to be free of the mite.[11] The Hawaiian islands of Maui, Kauai, Molokai, and Lanai are all free of the mite.

Identification

Until recently, V. destructor was thought to be a closely related mite species called Varroa jacobsoni. Both species parasitize the Asian honey bee, Apis cerana. However, the species originally described as V. jacobsoni by Anthonie Cornelis Oudemans in 1904 is not the same species that also attacks Apis mellifera. The jump to A. mellifera probably first took place in the Philippines in the early 1960s where imported A. mellifera came into close contact with infected A. cerana. Until 2000, scientists had not identified V. destructor as a separate species. This late identification in 2000 by Anderson and Trueman corrected some previous confusion and mislabeling in the scientific literature.[12]

Varroosis

The infection and subsequent parasitic disease caused by varroa mites is called varroosis. Sometimes, the incorrect names varroatosis or varroasis are used. A parasitic disease name must be formed from the taxonomic name of the parasite and the suffix -osis[13] as provided in the Standardised Nomenclature by the World Association for the Advancement of Veterinary Parasitology.[14] For example, the World Organisation for Animal Health (OIE) uses the name varroosis in the OIE Terrestrial Manual.[15]

Treatments have met with limited success. First, the bees were medicated with fluvalinate, which had about 95% mite falls. However, the last 5% became resistant to it, and later, almost immune. Fluvalinate was followed by coumaphos.

Control or preventive measures and treatment

Honeybee coated with oxalic acid to protect from mites

Chemical measures

Varroa mites can be treated with commercially available miticides. Miticides must be applied carefully to minimize the contamination of honey that might be consumed by humans. Proper use of miticides also slows the development of resistance by the mites.

Synthetic chemicals

Naturally occurring chemicals

Physical, mechanical, behavioral methods

Varroa mites can also be controlled through nonchemical means. Most of these controls are intended to reduce the mite population to a manageable level, not to eliminate the mites completely.

Genetic engineering

Researchers have been able to use RNA interference to knock out genes in the Varroa mite. There have also been efforts to breed for changes in the honey bees. Two strains have been developed in the United States that can detect damaged pupae under cappings and remove them before the infestation spreads further.[22][23] Another strain is under development that can more easily recognize adult phoretic varroa so they can be groomed and removed from the hive.

See also

References

  1. ↑ Ernesto Guzmán-Novoa, Leslie Eccles, Yireli Calvete, Janine Mcgowan, Paul G. Kelly & Adriana Correa-Benítez (2009). "Varroa destructor is the main culprit for the death and reduced populations of overwintered honey bee (Apis mellifera) colonies in Ontario, Canada" (PDF). Apidologie 41 (4): 443–450. doi:10.1051/apido/2009076.
  2. ↑ Welsh, Jennifer (7 June 2012) Mites and Virus Team Up to Wipe Out Beehives Live Science, Retrieved 11 June 2012
  3. ↑ J. Raloff (August 8, 1998). "Russian queens bee-little mites' impact" 154 (6). Science News: 84.
  4. ↑ Peter G. Kevan, Terence M. Laverty & Harold A. Denmark (1990). "Association of Varroa jacobsoni with organisms other than honeybees and implications for its dispersal". Bee World 71 (3): 119–121.
  5. ↑ Helen M. Thompson, Michael A. Brown, Richard F. Ball & Medwin H. Bew (2002). "First report of Varroa destructor resistance to pyrethroids in the UK" (PDF). Apidologie 33 (4): 357–366. doi:10.1051/apido:2002027.
  6. ↑ "Varroa Mite, Varroa destructor". MAF Biosecurity New Zealand. June 30, 2009. Retrieved February 24, 2011.
  7. ↑ Nina Wu (April 25, 2007). "Bee mites have spread on Oahu". Honolulu Star-Bulletin. Retrieved February 24, 2011.
  8. ↑ "Varroa Mite Information". State of Hawaii. 2013. Retrieved December 9, 2013.
  9. ↑ Holland, Malcolm (June 26, 2012). "Varroa mites could devastate our honeybee industry". The Sydney Morning Herald. Retrieved June 26, 2012.
  10. ↑ Jopson, Debra (August 18, 2010). "It's a bee nuisance – and food growers are more than a mite scared". The Sydney Morning Herald. Retrieved June 20, 2012.
  11. ↑ "Honigbienenart in der Sahara entdeckt" [Honey bee species discovered in the Sahara] (in German). Die Zeit. July 2010. Retrieved February 24, 2011.
  12. ↑ D. L. Anderson & J. W. H. Trueman (2000). "Varroa jacobsoni (Acari: Varroidae) is more than one species". Experimental and Applied Acarology 24 (3): 165–189. doi:10.1023/A:1006456720416. PMID 11108385.
  13. ↑ Kassai T., 2006, Nomenclature for parasitic diseases: cohabitation with inconsistency for how long and why?, Veterinary Parasitology, 138, 169–178, http://www.waavp.org/files/Nomenclature%20for%20parasitic%20diseases.pdf
  14. ↑ http://www.waavp.org/node/43
  15. ↑ http://www.oie.int/fileadmin/Home/eng/Health_standards/tahm/2.02.07_VARROOSIS.pdf
  16. ↑ Mark Ward (March 8, 2006). "Almond farmers seek healthy bees". BBC News. Retrieved May 2, 2009.
  17. ↑ Natalia Damiani, Liesel B. Gende, Pedro Bailac, Jorge A. Marcangeli & Martín J. Eguaras (2009). "Acaricidal and insecticidal activity of essential oils on Varroa destructor (Acari: Varroidae) and Apis mellifera (Hymenoptera: Apidae)". Parasitology Research 106 (1): 145–152. doi:10.1007/s00436-009-1639-y. PMID 19795133.
  18. ↑ Northeast Beekeeper Vol 1 #1 Jan 2004)
  19. 1 2 John R. Harbo (2000). "Heating Adult Honey Bees to Remove Varroa jacobsoni" (PDF). Journal of Apicultural Research 39 (3-4): 181–183.
  20. 1 2 http://www.reuters.com/article/2015/05/28/us-czech-bees-idUSKBN0OD20S20150528
  21. ↑ US application 2014134920
  22. ↑ "A Sustainable Approach to Controlling Honey Bee Diseases and Varroa Mites". SARE. Retrieved 2008-11-18.
  23. ↑ Victoria Gill (December 22, 2010). "Genetic weapon developed against honeybee-killer". BBC News. Retrieved February 24, 2011.

Further reading

External links

Wikispecies has information related to: Varroa destructor
Wikimedia Commons has media related to Varroa destructor.
This article is issued from Wikipedia - version of the Thursday, March 17, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.