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Title: VARROA-INFESTED CELLS THAT ARE NOT REMOVED BY BEES WITH VARROA-SENSITIVE HYGIENE

Author
item HARBO, JOHN - RETIRED ARS
item Harris, Jeffrey

Submitted to: American Bee Research Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 1/9/2006
Publication Date: 5/1/2006
Citation: Harbo, J.R., Harris, J.W. 2006. Varroa-infested cells that are not removed by bees with varroa-sensitive hygiene. American Bee Journal 146(5):447-448

Interpretive Summary:

Technical Abstract: The mite-resistance trait called suppression of mite reproduction (SMR) can be explained by a form of hygienic behavior that we call varroa sensitive hygiene (VSH). With VSH, adult honey bees remove worker-bee pupae from brood cells infested with Varroa destructor. Objectives were (1) to define which brood cells are removed by bees and which are not and (2) to describe the most effective way to measure VSH. We produced 35 colonies that ranged from having 0 to 100% expression of VSH. The nearly continuous distribution of colony phenotypes from low to high suggests that most or all of the genes for VSH are additive, differing from the recessive genes that control hygiene for resistance to American foulbrood (Rothenbuhler, Am. Zool. 4:111-123). We measured both the removal of infested cells and the frequency of nonreproducing mites in all colonies. An increase in the rate of removal of infested cells was strongly related to a decrease in all categories of reproductive mites, even mites that produced eggs too late to mature. However, removal rates were not related to the number of mites that produced no progeny. This selective removal of egg-laying mites creates an increase in the proportion of mites that lay no eggs. Therefore, the simplest way to measure VSH is to measure the frequency of mites that lay no eggs. For example, a population of mites typically has those that enter cells but do not lay eggs. The average frequency of these nonreproducing mites is about 12%. When examining worker cells that are >7 days postcapping, a colony that has 12% of the mites with no eggs has had little or no removal of infested cells and probably has none of the genes that express VSH. When 45, 70, or 100% of the infested cells have mites that lay no eggs, the colony has about 50, 75 or 100%, respectively, of the genes that express VSH.