Towards integrated control of varroa: effect of variation in hygienic behaviour among honey bee colonies on mite population increase and deformed wing virus incidence

Abstract

SummaryHygienic behaviour in the honey bee, Apis mellifera, is the uncapping and removal of dead, diseased or infected brood from sealed cells by worker bees. We determined the effect of hygienic behaviour on varroa population growth and incidence of deformed wing virus (DWV), which can be transmitted by varroa. We treated 42 broodless honey bee colonies with oxalic acid in early January 2013 to reduce varroa populations to low levels, which we quantified by extracting mites from a sample of worker bees. We quantified varroa levels, again when the colonies were broodless, 48 weeks later. During the summer the hygienic behaviour in each colony was quantified four times using the Freeze Killed Brood (FKB) removal assay, and ranged from 27.5 % to 100 %. Varroa population increased greatly over the season, and there was a significant negative correlation between varroa increase and FKB removal. This was entirely due to fully hygienic colonies with >95 % FKB having only 43 % of the varroa build up of the less hygienic colonies. None of the 14 colonies with >80 % FKB removal had overt symptoms of DWV, whilst 36 % of the less hygienic colonies did. Higher levels of FKB removal also correlated significantly with lower numbers of DWV RNA copies in worker bees, but not in varroa mites. On average, fully hygienic colonies had c. 10,000 times less viral RNA than less hygienic colonies. Hacia el control integrado de varroa: efecto de la variación en el comportamiento higiénico entre colonias de abejas de la miel con aumento de la población de ácaros y de la incidencia de virus de las alas deformadas ResumenEl comportamiento higiénico en la abeja de la miel, Apis mellifera, se basa en el desoperculado y la eliminación de la cría muerta, enferma o infectada a de las celdas selladas por las abejas obreras. Se determinó el efecto del comportamiento higiénico en el crecimiento de la población de varroa y la incidencia del virus de las alas deformadas (VAD), que puede ser transmitido por la varroa. Se han tratado 42 colonias de abejas de la miel sin larvas con ácido oxálico a principios de enero de 2013 para reducir las poblaciones de varroa a niveles bajos, lo que fue cuantificado mediante la extracción de los ácaros de una muestra de las abejas obreras. Se cuantificaron los niveles de varroa, de nuevo cuando las colonias no tenían cría, 48 semanas después. Durante el verano, el comportamiento higiénico en cada colonia se cuantificó cuatro veces utilizando el ensayo de congelar la cría para matarla (BCM), y este varió entre el 27,5% y el 100%. La población de Varroa aumentó considerablemente durante la temporada, y se observó una correlación negativa significativa entre el aumento de la varroasis y la 556 Toufailia et al.

Towards integrated control of varroa: 2)comparing application methods and doses of oxalic acid on the mortality of phoreticVarroa destructormites and their honey bee hosts

“…Depending on varroa population increase, the level of mite kill from OA sublimation may be sufficient for annual treatment in a winter broodless period without the use of additional control measures in combination with hygienic behavior. This seems to be the case in the study location (Al Toufailia, Amiri, Scandian, Kryger, & Ratnieks, 2014), especially for colonies that are also hygienic. If this is not the case then additional varroa control methods may be necessary.…”

Hygienic behaviour in Brazilian stingless bees

“…Their overall appearance was similar to that of honey bee workers with overt symptoms of deformed wing virus (DWV) (Al Toufailia et al, 2014). However, cDNA generated from RNA extracted from pooled samples of workers from both the diseased colony and healthy S. depilis colonies did not amplify for primers of DWV-F2 (strain A) and DWV-R2a (strain B) (McMahon et al, 2015).…”

“…Worker honey bees showing hygienic behaviour detect and uncap cells containing dead and infected brood, and remove the contents from the colony (Rothenbuhler, 1964a,b). Hygienic behaviour has been shown to help control varroa mites, deformed wing virus (DWV), chalkbrood, and American foulbrood (Al Toufailia et al, 2014; Spivak and Gilliam, 1998a,b; Wilson-Rich et al, 2009). Hygienic behaviour is not learned, rather, it is an instinctive heritable trait controlled by multiple genetic loci (Jones and Rothenbuhler, 1964; Momot and Rothenbuhler, 1971; Rothenbuhler, 1964a,b; Wilson-Rich et al, 2009).…”

Selection for resistance to Varroa destructor under commercial beekeeping conditions

“…For example, recent studies indicate that tolerance to the deformed wing virus may be under genetic control (Khongphinitbunjongaet et al, 2015;Locke, Forsgren, & de Miranda, 2014). Al Toufailia Amiri, Scandian, Kryger, and Ratnieks (2014) found that worker bees from colonies that were more than 95% hygienic had significantly fewer mites and lower levels of RNA copies of DWV. The ideal situation for beekeepers would be a mite-resistant bee that is both tolerant to the damage caused by the mites and the diseases they vector.…”