Bees are subject to numerous pressures in the modern world. The abundance and diversity of flowers has declined, bees are chronically exposed to cocktails of agrochemicals, and they are simultaneously exposed to novel parasites accidentally spread by humans. Climate change is likely to exacerbate these problems in the future. Stressors do not act in isolation; for example pesticide exposure can impair both detoxification mechanisms and immune responses, rendering bees more susceptible to parasites. It seems certain that chronic exposure to multiple, interacting stressors is driving honey bee colony losses and declines of wild pollinators, but such interactions are not addressed by current regulatory procedures and studying these interactions experimentally poses a major challenge. In the meantime, taking steps to reduce stress on bees would seem prudent; incorporating flower-rich habitat into farmland, reducing pesticide use through adopting more sustainable farming methods, and enforcing effective quarantine measures on bee movements are all practical measures that should be adopted. Effective monitoring of wild pollinator populations is urgently needed to inform management strategies into the future.

https://science.sciencemag.org/content/sci/early/2015/02/25/science.1255957.full.pdf

Bee declines driven by combined stress from parasites, pesticides, and lack of flowers

Summary 1. Neonicotinoids are now the most widely used insecticides in the world. They act systemically, travelling through plant tissues and protecting all parts of the crop, and are widely applied as seed dressings. As neurotoxins with high toxicity to most arthropods, they provide effective pest control and have numerous uses in arable farming and horticulture. 2. However, the prophylactic use of broad-spectrum pesticides goes against the long-established principles of integrated pest management (IPM), leading to environmental concerns. 3. It has recently emerged that neonicotinoids can persist and accumulate in soils. They are water soluble and prone to leaching into waterways. Being systemic, they are found in nectar and pollen of treated crops. Reported levels in soils, waterways, field margin plants and floral resources overlap substantially with concentrations that are sufficient to control pests in crops, and commonly exceed the LC50 (the concentration which kills 50% of individuals) for beneficial organisms. Concentrations in nectar and pollen in crops are sufficient to impact substantially on colony reproduction in bumblebees. 4. Although vertebrates are less susceptible than arthropods, consumption of small numbers of dressed seeds offers a route to direct mortality in birds and mammals. 5. Synthesis and applications. Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non-target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services.

/pdf/review-an-overview-of-the-environmental-risks-posed-by-hj0ee8p6bs.pdf

REVIEW: An overview of the environmental risks posed by neonicotinoid insecticides

Wild and managed pollinators provide a wide range of benefits to society in terms of contributions to food security, farmer and beekeeper livelihoods, social and cultural values, as well as the maintenance of wider biodiversity and ecosystem stability. Pollinators face numerous threats, including changes in land-use and management intensity, climate change, pesticides and genetically modified crops, pollinator management and pathogens, and invasive alien species. There are well-documented declines in some wild and managed pollinators in several regions of the world. However, many effective policy and management responses can be implemented to safeguard pollinators and sustain pollination services.

/pdf/safeguarding-pollinators-and-their-values-to-human-well-2dege9v9a6.pdf

Safeguarding pollinators and their values to human well-being

Growing evidence for declines in bee populations has caused great concern because of the valuable ecosystem services they provide. Neonicotinoid insecticides have been implicated in these declines because they occur at trace levels in the nectar and pollen of crop plants. We exposed colonies of the bumble bee Bombus terrestris in the laboratory to field-realistic levels of the neonicotinoid imidacloprid, then allowed them to develop naturally under field conditions. Treated colonies had a significantly reduced growth rate and suffered an 85% reduction in production of new queens compared with control colonies. Given the scale of use of neonicotinoids, we suggest that they may be having a considerable negative impact on wild bumble bee populations across the developed world.

https://science.sciencemag.org/content/sci/336/6079/351.full.pdf

Neonicotinoid Pesticide Reduces Bumble Bee Colony Growth and Queen Production

Declines in bumble bee species in the past 60 years are well documented in Europe, where they are driven primarily by habitat loss and declines in floral abundance and diversity resulting from agricultural intensification. Impacts of habitat degradation and fragmentation are likely to be compounded by the social nature of bumble bees and their largely monogamous breeding system, which renders their effective population size low. Hence, populations are susceptible to stochastic extinction events and inbreeding. In North America, catastrophic declines of some bumble bee species since the 1990s are probably attributable to the accidental introduction of a nonnative parasite from Europe, a result of global trade in domesticated bumble bee colonies used for pollination of greenhouse crops. Given the importance of bumble bees as pollinators of crops and wildflowers, steps must be taken to prevent further declines. Suggested measures include tight regulation of commercial bumble bee use and targeted use of environmentally comparable schemes to enhance floristic diversity in agricultural landscapes.

/pdf/decline-and-conservation-of-bumble-bees-1thgzzqlml.pdf

Decline and conservation of bumble bees

BACKGROUND: To date, in modern agriculture, biological control strategies are increasingly becoming the preferred pest management approach. However, the success of microbiological control agents (MCAs) largely depends on efficient dissemination into the crop. The pollinator-and-vector technology employs pollinating insects like bees for a better dissemination. In this study, a new dispenser for bumblebee workers of Bombus terrestris L. was developed. Binab-T-vector and Prestop-Mix were used as two typical MCA products for dissemination.



RESULTS: In a first series of experiments in the laboratory for optimisation, the newly developed dispenser was a two-way type dispenser, 20 cm long, with two rectangular compartments and different entrance and exit holes. In addition, the amounts of MCA loaded on the workers were 10 times higher with the new dispenser as compared with the side-by-side passageway (SSP) dispenser. Typically, the highest amounts were recovered from the thorax and legs of the workers. In a second series of experiments under greenhouse conditions with the use of queen-right B. terrestris hives, successful dissemination in strawberry flowers was obtained at different distances from the hive (0–8 m, 8–18 m and 18–21 m), and the workers inoculated the first, second and third flowers that were consecutively visited. In addition, the new dispenser caused no adverse effects on worker foraging intensity, whereas a dramatic reduction was scored with an SSP dispenser. Finally, the data suggested that it is necessary to refill the newly developed dispenser at 3 day intervals.



CONCLUSIONS: The results demonstrated that, with the use of the newly developed dispenser, bumblebee workers carried high amounts of MCA, and this resulted in a successful dissemination of MCA into strawberry flowers. Copyright © 2010 Society of Chemical Industry

Development of a new dispenser for microbiological control agents and evaluation of dissemination by bumblebees in greenhouse strawberries

The entomovector technology (Hokkanen and Menzler-Hokkanen 2007; Mommaerts and Smagghe 2011) utilizes insects as vectors of biological control agents for targeted precision biocontrol towards plant pests and diseases, providing an intriguing example of multitrophic interactions. As the insect vector normally is a pollinator of the crop plant, it adds a further dimension to these interactions. The technology depends on bee management, manipulation of bee behaviour, components of the cropping system, and on the plant-pathogen-vector-antagonist-system. We investigate in this chapter how to exploit and support the natural ecological functions of biocontrol and pollination, and enhance these via innovative management. Recent systematic developments of the entomovector technology are described, with focus on the component technologies such as the dispensers and carrier substances (see Mommaerts and Smagghe 2011; Mommaerts et al. 2011; Hokkanen et al. 2012). With functioning dispensers and improved, new microbiological control agents (MCA) available, excellent results have been obtained, and will be described in two case studies. The first involves open field studies conducted in Finland with honey bees (Apis mellifera Linnaeus (Hymenoptera: Apidae)) as the vector of “Prestop-Mix”, containing Gliocladium catenulatum J1446 (Hypocreales, Bionectriaceae), to control Botrytis cinerea Pers.: Fr. (Helotiales: Sclerotiniaceae) in strawberries, and the second describes the efficiency of bumble bees (Bombus terrestris Linnaeus (Hymenoptera: Apidae)) to vector the commercial product “Prestop-Mix” to control B. cinerea in strawberries in the greenhouse.

Multitrophic Interactions: The Entomovector Technology

In the context of integrated pest management with biological control and reduced pesticide use, dissemination of entomopathogenic fungi with insects has the potency to protect crops and specifically their flowers against pests and diseases. But before implementation of such entomovectoring system, a measurement of risks of the microbial biocontrol agent toward the vectoring insect is crucial. The essential contributions of this project are that 1) exposure of bumble bees, Bombus terrestris (L.) to powder containing 10(7) spores of the commercial biocontrol agent Metarhizium anisopliae strain F52 (Biol020) per gram, was safe; and 2) that when bumble bees had walked through this spore concentration (10(7) spores per gram) in a dispenser, their body carried 9.3 +/- 1 x 10(6) spores/bumble bee, and this was still 2.6 10(6) spores after a flight of 60 s, representing the average time to fly from the dispenser to the crop flowers. 3) In contrast, a 100-fold higher spore concentration (10(9) spores per gram powder) was highly toxic and the acquisition on the bumble bee body was only 2.5 times higher. Based on these data, future studies can start investigating the protection efficacy of this entomovector system with M. anisopliae and bumble bees without harming the vector and with a loading of the vector considered enough to obtain a good inoculation into and protection of the flowers.

https://bioone.org/journals/journal-of-economic-entomology/volume-106/issue-1/EC12332/Safety-and-Acquisition-Potential-of-Metarhizium-anisopliae-in-Entomovectoring-with/10.1603/EC12332.pdf

Safety and Acquisition Potential of Metarhizium anisopliae in Entomovectoring With Bumble Bees, Bombus terrestris

BACKGROUND: Entomovectoring as a plant protection strategy demands the design of an appropriate bioassay to assess the risks of potential side effects of the powder formulations in the dispenser towards the vectoring insect. This study reports on the development of a laboratory miniature-dispenser-based bioassay. This bioassay system was used to investigate the compatibility of five model products, Prestop-Mix, Signum, kaolin, wheat flour and cellulose, with the bumblebee, Bombus terrestris L.



RESULTS: The laboratory one-way miniature-dispenser bioassay showed that the fungicides and the carrier/diluent kaolin caused a worker mortality of > 70% after 5 weeks of exposure, while worker loss with wheat flour and cellulose was no higher than in the blank control (i.e. empty miniature dispenser) (<25%). The laboratory two-way miniature-dispenser bioassay comprised separated passageways and demonstrated that only kaolin was toxic (89 ± 11%). These results were also confirmed in a flight-cage experiment. In addition, a negative effect was observed against reproduction/colony development when nests were exposed to kaolin (P < 0.05) in the two-way miniature-dispenser and flight-cage bioassays.



CONCLUSIONS: In the context of entomovectoring technology, the developed laboratory two-way miniature-dispenser bioassay gives a reliable prediction of the hazards associated with powder products. Additionally, the present data indicate the possibility of using cellulose and kaolin as respective negative and positive control carriers/diluents in future risk assessment experiments. Overall, the results show that, apart from kaolin, the tested fungicides and carriers/diluents are safe to be used with B. terrestris. Copyright © 2011 Society of Chemical Industry

Miniature-dispenser-based bioassay to evaluate the compatibility of powder formulations used in an entomovectoring approach.

Bumblebees are important pollinators in natural and agricultural ecosystems. The latter results in the frequent exposure of bumblebees to pesticides. We report here on a new bioassay that uses primary cultures of neurons derived from adult bumblebee workers to evaluate possible side-effects of the neonicotinoid pesticide imidacloprid. Mushroom bodies (MBs) from the brains of bumblebee workers were dissected and dissociated to produce cultures of Kenyon cells (KCs). Cultured KCs typically extend branched, dendrite-like processes called neurites, with substantial growth evident 24-48 h after culture initiation. Exposure of cultured KCs obtained from newly eclosed adult workers to 2.5 parts per billion (ppb) imidacloprid, an environmentally relevant concentration of pesticide, did not have a detectable effect on neurite outgrowth. By contrast, in cultures prepared from newly eclosed adult bumblebees, inhibitory effects of imidacloprid were evident when the medium contained 25 ppb imidacloprid, and no growth was observed at 2,500 ppb. The KCs of older workers (13-day-old nurses and foragers) appeared to be more sensitive to imidacloprid than newly eclosed adults, as strong effects on KCs obtained from older nurses and foragers were also evident at 2.5 ppb imidacloprid. In conclusion, primary cultures using KCs of bumblebee worker brains offer a tool to assess sublethal effects of neurotoxic pesticides in vitro. Such studies also have the potential to contribute to the understanding of mechanisms of plasticity in the adult bumblebee brain.

Veerle Mommaerts

Papers

Development of a new dispenser for microbiological control agents and evaluation of dissemination by bumblebees in greenhouse strawberries

Multitrophic Interactions: The Entomovector Technology

Safety and Acquisition Potential of Metarhizium anisopliae in Entomovectoring With Bumble Bees, Bombus terrestris

Miniature-dispenser-based bioassay to evaluate the compatibility of powder formulations used in an entomovectoring approach.

Use of primary cultures of kenyon cells from bumblebee brains to assess pesticide side effects