Nicholas J. Balfour

Landscape Scale Study of the Net Effect of Proximity to a Neonicotinoid-Treated Crop on Bee Colony Health

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.

Using the waggle dance to determine the spatial ecology of honey bees during commercial crop pollination

Managed honey bees play an important role in global crop pollination. Maximizing their potential is likely to be of increasing importance to the human food supply. We explored the potential of waggle dance data to determine the spatial ecology of honey bees sited in a crop under commercial pollination. Over two springs, we video recorded and then decoded 834 waggle dances from colonies located in two apple and pear farms in Kent, U.K. We also obtained pollen samples from returning foragers and quantified the insects visiting apple and pear flowers. The vast majority (84%) of dances were for locations outside of the orchards in which our colonies were located. Accounting for the distance of orchards and oilseed rape fields from the study colonies, the amount of foraging per hectare in oilseed rape fields was greater than in orchards. The results of the present study indicate that maximizing the pollination services of managed honey bee colonies requires an landscape level approach that takes into account farm and foraging scale, as well as competing floral sources. The data also suggest that oilseed rape is a significant competitor to apple and pear flowers for honey bee visits.

Gut microbiota composition is associated with environmental landscape in honey bees.

Abstract There is growing recognition that the gut microbial community regulates a wide variety of important functions in its animal hosts, including host health. However, the complex interactions between gut microbes and environment are still unclear. Honey bees are ecologically and economically important pollinators that host a core gut microbial community that is thought to be constant across populations. Here, we examined whether the composition of the gut microbial community of honey bees is affected by the environmental landscape the bees are exposed to. We placed honey bee colonies reared under identical conditions in two main landscape types for 6 weeks: either oilseed rape farmland or agricultural farmland distant to fields of flowering oilseed rape. The gut bacterial communities of adult bees from the colonies were then characterized and compared based on amplicon sequencing of the 16S rRNA gene. While previous studies have delineated a characteristic core set of bacteria inhabiting the honey bee gut, our results suggest that the broad environment that bees are exposed to has some influence on the relative abundance of some members of that microbial community. This includes known dominant taxa thought to have functions in nutrition and health. Our results provide evidence for an influence of landscape exposure on honey bee microbial community and highlight the potential effect of exposure to different environmental parameters, such as forage type and neonicotinoid pesticides, on key honey bee gut bacteria. This work emphasizes the complexity of the relationship between the host, its gut bacteria, and the environment and identifies target microbial taxa for functional analyses.

Quality versus quantity: foraging decisions in the honeybee (Apis mellifera scutellata) feeding on wildflower nectar and fruit juice

Abstract Foraging animals must often decide among resources which vary in quality and quantity. Nectar is a resource that exists along a continuum of quality in terms of sugar concentration and is the primary energy source for bees. Alternative sugar sources exist, including fruit juice, which generally has lower energetic value than nectar. We observed many honeybees (Apis mellifera scutellata) foraging on juice from fallen guava (Psidium guajava) fruit near others foraging on nectar. To investigate whether fruit and nectar offered contrasting benefits of quality and quantity, we compared honeybee foraging performance on P. guajava fruit versus two wildflowers growing within 50 m, Richardia brasiliensis and Tridax procumbens. Bees gained weight significantly faster on fruit, 2.72 mg/min, than on either flower (0.17 and 0.12 mg/min, respectively). However, the crop sugar concentration of fruit foragers was significantly lower than for either flower (12.4% vs. 37.0% and 22.7%, respectively). Fruit foragers also spent the most time handling and the least time flying, suggesting that fruit juice was energetically inexpensive to collect. We interpret honeybee foraging decisions in the context of existing foraging models and consider how nest‐patch distance may be a key factor for central place foragers choosing between resources of contrasting quality and quantity. We also discuss how dilute solutions, such as fruit juice, can help maintain colony sugar–water balance. These results show the benefits of feeding on resources with contrasting quality and quantity and that even low‐quality resources have value.

[Review] Have suitable experimental designs been used to determine the effects of neonicotinoid insecticides on bee colony performance in the field?

Laboratory studies have shown than neonicotinoid insecticides can cause sub-lethal effects on bees. Field studies are needed to determine whether these effects also occur when bees forage on flowering crops grown from neonicotinoid-treated seeds. However, for many reasons the results of field experiments may be inconsistent. For example, neonicotinoid residues in crop nectar and pollen and the availability of alternative nectar and pollen sources vary. In addition to these practical difficulties, different field experiment designs, especially different controls, address different questions. Most field studies on neonicotinoids have compared the performance of colonies adjacent to a bee-attractive crop grown from treated seeds with control colonies adjacent to the same crop grown from untreated seeds. This makes it possible to determine the cost, C, of any insecticide residues but not the overall effect of the crop, B – C, which includes any benefits, B, of the additional pollen and nectar. An alternative and rarely used design, only 1 of the 12 field studies reviewed, determines the overall effect of the crop by siting control colonies out of foraging range of the crop but in the same landscape. This design may be more relevant because bee-attractive crops, such as oilseed rape, are normally grown as alternatives to arable crops that do not provide bee forage, such as wheat and barley. As a result, it is possible that B – C > 0 (or B – C = 0) even if C > 0. The challenges and merits of alternative experimental designs are discussed in relation to practical considerations and policy making. Determinación de los efectos de los insecticidas neonicotinoides en el rendimiento de las colonias de abejas en el campo: ¿qué prueban los diferentes diseños experimentales? Estudios de laboratorio han demostrado que los insecticidas neonicotinoides pueden causar efectos subletales en las abejas. Se necesitan estudios de campo para determinar si estos efectos también se producen cuando las abejas se alimentan de los cultivos en flor que crecen a partir de semillas tratadas con neonicotinoides. Sin embargo, por muchas razones los resultados de los experimentos de campo pueden ser inconsistentes. Por ejemplo, los residuos de neonicotinoides en el néctar y el polen de los cultivos y la disponibilidad de fuentes alternativas de néctar y polen varían. Además de estas dificultades prácticas, diferentes diseños de experimentos de campo, especialmente diferentes controles, abordan diferentes cuestiones. La mayoría de los estudios de campo sobre los neonicotinoides han comparado el rendimiento de las colonias adyacentes a un cultivo atractivo para las abejas cultivado a partir de semillas tratadas con colonias de control adyacentes al mismo cultivo cultivado a partir de semillas no tratadas. Esto permite determinar el coste, C, de cualquier residuo de insecticida, pero no el efecto global del cultivo, B–C, que incluye cualquier beneficio, B, del polen y néctar adicionales. Un diseño alternativo y raramente utilizado, sólo en 1 de los 12 estudios de campo revisados, determina el efecto general del cultivo al situar las colonias de control fuera del rango de alimentación del cultivo pero en el mismo paisaje. Este diseño puede ser más relevante porque los cultivos atractivos para las abejas, como la colza, se cultivan normalmente como alternativas a los cultivos herbáceos que no proporcionan forraje a las abejas, como el trigo y la cebada. Como resultado, es posible que B−C > 0 (o B−C = 0) incluso si C > 0. Los desafíos y los méritos de los diseños experimentales alternativos se discuten en relación con las consideraciones prácticas y la formulación de políticas.