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.

In the past two decades, the parasitic mite Varroa destructor has become harder to control with synthetic acaricide chemicals due to genetic resistance. We determined the efficacy of the natural chemical oxalic acid (OA) in killing phoretic mites on adult worker bees under field conditions in southern England. We compared three OA application methods (trickling, spraying, and sublimation) at three or four (sublimation) doses, using 110 broodless colonies in early January 2013. Treatment efficacy was assessed by extracting mites from samples of c. 270 worker bees collected immediately before and 10 days after treatment. All three methods could give high varroa mortality, c. 93-95%, using 2.25 g OA per colony. However, sublimation was superior as it gave higher mortality at lower doses (.56 or 1.125 g per colony: trickling 20, 57% mortality; spraying 25, 86%; sublimation 81, 97%.). Sublimation using 2.25 g of OA also resulted in 3 and 12 times less worker bee mortality in the 10 days after application than either trickling or spraying, respectively, and lower colony mortality four months later in mid spring. Colonies treated via sublimation also had greater brood area four months later than colonies treated via trickling, spraying, or control colonies. A second trial in December 2013 treated 89 broodless colonies with 2.25 g OA via sublimation to confirm the previous results. Varroa mortality was 97.6% and 87 (98%) of the colonies survived until spring. This confirms that applying OA via sublimation in broodless honey bee colonies in winter is a highly effective way of controlling V. destructor and causes no harm to the colonies.Hacia el control integrado de varroa: comparació n de mé todos de aplicació n y dosis de ácido oxálico en la mortalidad de ácaros foré ticos de Varroa destructor y sus abejas hosperadoras En los últimos años el ácaro parásito Varroa destructor se ha hecho más difícil de controlar debido a la resistencia a los acaricidas sintéticos utilizados. Se determinó la eficacia del ácido oxálico matando ácaros foréticos en abejas obreras adultas en condiciones de campo en el sur de Inglaterra. Se compararon tres métodos ya utilizados por los apicultores (goteo y pulverizació n de una solució n de sacarosa y ácido oxálico, y sublimació n) en tres o cuatro dosis en un experimento con 110 colonias sin cría, a principios de enero de 2013. La mortalidad de los ácaros se determinó mediante la extracció n de ácaros a partir de muestras de cerca de 270 abejas obreras recogidas inmediatamente antes y 10 días después del tratamiento. Los tres métodos podrían dar una alta mortalidad de Varroa, c. 93-95%, utilizando 2,25 g de ácido oxálico por colonia. Sin embargo, la sublimació n dio mayor mortalidad en dosis más bajas (0,56 o 1,125g por colonia: goteo 20, 57%; pulverizació n 25, 86%; sublimació n 81, 97%.). La sublimació n utilizando 2,25 g de ácido oxálico dio lugar a 3 y 12 veces menos mortalidad de abejas obreras en los 10 días después de la aplicació n que con goteo o aspersió n, respectivamente. La sublim...

Since 2013, the European Commission has restricted the use of three neonicotinoid insecticides as seed dressings on bee-attractive crops. Such crops represent an important source of forage for bees, which is often scarce in agro-ecosystems. However, this benefit has often been overlooked in the design of previous field studies, leaving the net impact of neonicotinoid treated crops on bees relatively unknown. Here, we determine the combined benefit (forage) and cost (insecticide) of oilseed rape grown from thiamethoxam-treated seeds on Bombus terrestris and Apis mellifera colonies. In April 2014, 36 colonies per species were located adjacent to three large oilseed rape fields (12 colonies per field). Another 36 were in three nearby locations in the same agro-ecosystem, but several kilometers distant from any oilseed rape fields. We found that Bombus colony growth and reproduction were unaffected by location (distant versus adjacent) following the two month flowering period. Apis colony and queen survival were unaffected. However, there was a small, but significant, negative relationship between honey and pollen neonicotinoid contamination and Apis colony weight gain. We hypothesize that any sublethal effects of neonicotinoid seed dressings on Bombus colonies are potentially offset by the additional foraging resources provided. A better understanding of the ecological and agronomic factors underlying neonicotinoid residues is needed to inform evidence-based policy.

1. One of the major challenges faced by pollinators worldwide is the reduction in their food supply, nectar, and pollen. Given the considerable seasonal variation in the abundance of both floral resources and flower-visiting insects, conservation initiatives aiming to help pollinators through floral resource supplementation could increase their impacts by targeting periods when the foraging conditions are most difficult. Direct assessment of foraging conditions, however, is extremely labour-intensive. 2. Here, we compared eight practical measures expected to reflect the foraging difficulty for nectar in the environment. Five measures involved Apis melliferaan indicator species for the flower-visitor guild due to its generalist, energetically optimal, and longdistance foraging habit. These included (i) visitation at feeders with a range of sucrose concentrations, (ii) guarding and (iii) fighting levels at hive entrances, (iv) rates of hive weight changes, and (v) foraging distances encoded in waggle dances. The other measures were (vi-viii) counts of flower-visiting insects in relation to the rate of nectar sugar secretion in three plant species attractive to flower-visiting insects. 3. There was considerable, although not complete agreement among the eight measures. Eleven of 28 pairwise correlations were statistically significant. Guarding and fighting correlated with most (five) other measures. We conclude that seven of the eight measures could be potentially useful in gauging seasonal patterns in local foraging conditions, which could help guide targeted conservation initiatives. Assessment of guarding and fighting levels at A. mellifera hive entrances is recommended, as these correlated significantly with most other measures and are easy to obtain in practice.

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