Thursday, February 9, 2012

Varroa Sensitive Hygiene

Varroa mite on queen bee
     The varroa mite is a small mite (approximately 1 mm in diameter) native to Asia and the Asian honey bee (Apis Cerana) which has developed a resistance to the mite enabling it to cope with it's presence. Russian honey bees from the eastern Primorsky territory have also developed a resistance to the mite (The U.S.D.A and Mite Resistant Honey Bees).  Here is a history of the U.S.D.A's Russian Honey Bee Queen Breeding Project (History).


     Over the last 50 years the varroa has spread from country to country having become a major threat in the last decade to both the native and honeybee populations throughout the world.  This blood sucking parasite transmits a number of honey bee diseases (Some of the viruses transmitted by the Varroa Mite).


Worldwide spread of the Varroa mite

     
     Australia remains the only beekeeping nation free of the varroa destructor mite.  In Canada the island portion of Newfoundland remains varroa free.  
     There are many methods of treating your hives for mites (Varroa Mite controls) such as pesticides (Apistan and Checkmite), formic or oxalic acid,  sugar dusting, screened bottom boards and brood breaks.  Mites have shown a resistance to the pesticides and it's suggested that a combination of methods must be applied.
     I believe the future of dealing with varroa will be breeding for varroa sensitive hygienic (VSH) behavior.  In hives with VSH behavior bees, bee pupae infected with mites are detected and removed.  Other VSH behavior traits include: more effective self grooming; group grooming; guard bees removing mites from bees entering the hive (either killing the mites or chasing them from the hive) and bees using their mandibles to kill the mites.  For a more detailed description of breeding for mite resistance check out ScientificBeekeeping


     
     In the picture above the bees are chewing on a mite infested bee larvae.   It is important to remember that Asian honey bees (Apis cerana), African honey bees (Apis mellifera scutellata), Africanized honey bees (hybrid European and African) and a strain of Russian honey bees are effectively resistant (VSH behavior) to the varroa mite.  Most bee breeders are breeding for VSH traits including  Glenn Apiaries  which sells VSH queens.
     The video below shows bees displaying some VSH traits such as aggressive grooming and biting. 




     This year  I will be checking my mite test boards for signs of the varroa being bitten (missing legs).  A screened bottom board is a valuable tool for any beekeeper with mites. The screened bottom board allows removed mites to fall out of the hive and as a bonus increases much needed circulation but the alcohol wash or sugar shake will give you a more accurate mite measurement (Mite Monitoring Methods).
     For further information on hygienic behaviour in honey bees go to the Hygienic Behaviour section of our Beekeepers' Library.


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