Sub-lethal pesticide exposure interferes with honey bee memory of learnt colours

Neonicotinoid pesticide use has increased around the world despite accumulating evidence of their potential detrimental sub-lethal effects on the behaviour and physiology of bees, and its contribution to the global decline in bee health. Whilst flower colour is considered as one of the most important signals for foraging honey bees (Apis mellifera), the effects of pesticides on colour vision and memory retention in a natural setting remain unknown. We trained free flying honey bee foragers by presenting artificial yellow flower feeder, to an unscented artificial flower patch with 6 different flower colours to investigate if sub-lethal levels of imidacloprid would disrupt the acquired association made between the yellow flower colour from the feeder and food reward. We found that for doses higher than 4 % of LD50 value, the foraging honey bees no longer preferentially visited the yellow flowers within the flower patch and instead, we suspect, reverted back to baseline foraging preferences, with a complete loss of the yellow preference. Our honey bee colour vision modelling indicates that discriminating the yellow colour from the rest should have been easy cognitive task. Pesticide exposure also resulted in a significant increase in Lop1, UVop, and Blop, and a decrease in CaMKII and CREB gene expression. Our results suggest that memory loss is the most plausible mechanism to explain the alteration of bee foraging colour preference. Across bees, colour vision is highly conserved and is essential for efficient pollination services. Therefore, our findings have important implications for ecosystem health and agricultural services world-wide.

Honey Bee Pathogen Prevalence and Interactions within the Marmara Region of Turkey

Beekeeping has yet to reach its full potential in terms of productivity in Turkey where it has a relatively large role in the economy. Poor colony health is suspected to be the reason for this, but comprehensive disease monitoring programs are lacking to support this notion. We sampled a total of 115 colonies across five different apiaries throughout the Marmara region of Turkey and screened for all of the major bee pathogens using PCR and RNA-seq methods. We found that Varroa mites are more prevalent in comparison to Nosema infections. The pathogens ABPV, DWV, KV, and VDV1 are near 100% prevalent and are the most abundant across all locations, which are known to be vectored by the Varroa mite. We therefore suspect that controlling Varroa mites will be key for improving bee health in Turkey moving forward. We also documented significant interactions between DWV, KV, and VDV1, which may explain how the more virulent strain of the virus becomes abundant. ABPV had a positive interaction with VDV1, thereby possibly facilitating this more virulent viral strain, but a negative interaction with Nosema ceranae. Therefore, these complex pathogen interactions should be taken into consideration in the future to improve bee health.

Decreased efficiency of pollen collection due to Sulfoxaflor exposure leads to a reduction in the size of bumble bee workers in late European summer

Bumble bees (Bombus terrestris) are important pollinators of wild and crop plants. Despite their importance in the process of fruit and seed production on crop sites, their activity may be impaired due to exposure to pesticides. This species has a yearly life cycle and colony success may rely on effective foraging of workers on ruderal plants late in summer when most crops are no longer flowering. In the current study, we investigated the effect of chronic exposure to Sulfoxaflor on aspects of the foraging behavior of bumble bees and whether Sulfoxaflor influences the body size of workers of B. terrestris in a crop landscape. We found that 2 weeks of continuous exposure to Sulfoxaflor influenced workers’ foraging dynamics and collection of resources. However, there was no evidence that the 5 ppb dose of the pesticide impacted the ability of bees to handle flowers with different traits. Workers from colonies exposed to Sulfoxaflor were smaller. The effect on worker size may be explained as a consequence of the reduced pollen income per unit of worker foraging. Thus, if the effects of Sulfoxaflor applied directly to crops had the same effect as that observed on commercial bumble bees after our chronic exposure, it might negatively impact colony success due to the impact on pollen collection and the reduction in the size of workers.

The development of the solitary bee Osmia bicornis is affected by some insecticide agrochemicals at environmentally relevant concentrations

Solitary bees provide essential pollination services for many arable crops, but are prone to global decline. Agricultural intensification, which is connected with pesticide usage, is among major threats to bees and, thus, to the food security and ecosystem stability. As it may not be possible to cease pesticide usage currently because of the growing demand for food, it is crucial to understand the pesticide toxicities to bees for better protection of pollinator populations. The majority of studies have focused on social bees, and those on solitary bees studied effects of adult exposure, whereas these bees are also likely to be exposed as larvae via the consumption of contaminated pollen. Here, the effects of three commonly used insecticide-based plant protection products on the development of the solitary bee, Osmia bicornis (red mason bee), were studied by exposing larvae to insecticide-contaminated multifloral pollen. The tested insecticides were: Dursban480EC, containing the organophosphate chlorpyrifos (CHP), Sherpa100EC, containing the pyrethroid cypermethrin (CYP), and Mospilan20SP with the neonicotinoid acetamiprid (ACT). When compared to the control larvae fed with uncontaminated-pollen, both CHP and CYP significantly reduced the O. bicornis larval survival and their body mass at all tested concentrations. In contrast, ACT did not affect either larval survival or body mass, but the length of larval stage to cocoon formation was significantly shortened compared to controls. None of studied insecticides affected the mass of cocooned individuals. However, at least 80% of individuals exposed to any of the tested insecticides died before reaching the adult stage, whereas 43% of the controls emerged successfully after overwintering. Although no clear monotonic dose-response relationships were found, our study showed that at least some insecticide formulations affect the development of O. bicornis even at concentrations actually found in pollen in the field, indicating an urgent need for revising current pesticide usage recommendations.