Annotated Bibliography of Select Research Articles Regarding Pesticide Impacts to Pollinators
Research Released Since May 2015
This is not a comprehensive bibliography of pesticide articles. The emphasis is on studies on neonicotinoids as well as other pesticides that demonstrate novel concerns.
Arce, A.N., T.I. David, E.L. Randall, A. Ramos Rodrigues, T.J. Colgan, Y. Wurm, and R.J. Gill. 2016. Journal of Applied Ecology. doi: 10.1111/1365-2664.12792.
Impact of controlled neonicotinoid exposure on bumblebees in a realistic field setting.
This field study found that after a five week exposure to field realistic levels of clothianidin (5 ppb) bumble bee colonies had fewer adult workers, drones and gynes compared to untreated colonies. The researchers did not find a difference in colony mass between the treated and untreated colonies. By measuring foraging and pollen collection through multiple methods, the researchers were also able to identify subtle changes to the pattern of foraging activity.
Botias, C., A. David, E. M. Hill, and D. Goulson. 2016. Science of the Total Environment. doi:10.1016/j.scitotenv.2016.05.065.
Contamination of wild plants near neonicotinoid seed-treated crops, and implications for non-target insects.
A companion to David et al. (2016), this study analyzed samples of foliage of oilseed rape grown from coated seed, as well as plants growing in the field margins (1–2 meters from crops). The maximum detected residues were compared to lethal doses of relevant insect species. While residue levels were variable, some levels overlapped with lethal concentrations. Furthermore, 52% of foliage samples from field margins had at least one neonicotinoid, and 46.3% of foliage samples had detectable levels of two or more neonicotinoids. Other findings of note include that imidacloprid hadn’t been used in at least 3 years but it was still found in 20% of the field margin foliage tested. Providing insight into how different plants uptake neonicotinoids, researchers noted that pesticide concentrations were higher in annuals than perennials. Similarly, concentrations were significantly higher in herbaceous plants than woody.
Brandt, A., A. Gorenflo, R. Siede, M. Meixner, and R. Buchler. 2016. Journal of Insect Physiology. 86:40–47.
The neonicotinoids thiacloprid, imidacloprid, and clothianidin affect the immunocompetence of honey bees (Apis mellifera L.).
Building on existing research associating pesticide use with a reduction in honey bee immune system function, this study measured the impact of three neonicotinoids, clothianidin, imidacloprid and thiacloprid, on three distinct immune defense mechanisms. The study found that both imidacloprid and thiacloprid weakened individual bee’s immune responses at field realistic doses of 1 ug/L and 200 ug/L respectively. Clothianidin only impacted the immune parameters at levels higher than the researchers considered to be field relevant (50–200 ug/L). The results of this study suggest that field-realistic sublethal exposures levels of imidacloprid and thiacloprid can affect the immunocompetence of individual honey bees. These effects could reduce the capacity of honey bees to resist disease and survive attacks from parasites.
David, A., C. Botias, A. Abdul-Sada, E. Nicholls, E. L. Rotheray, E. M. Hill, and D. Goulson. 2016. Environment International. doi:10.1016/j.envint.2015.12.011.
Widespread contamination of wildflower and bee-collected pollen with complex mixtures of neonicotinoids and fungicides commonly applied to crops.
This study evaluated contamination of wildflowers located within 1 to 2 meters of agricultural fields where oilseed rape was grown. Focusing on the contamination of neonicotinoid insecticides and fungicides the authors found that both flowering crops and adjacent wildflowers were “heavily” contaminated with a broad range of pesticides. The frequency, range, and mean concentration of pesticides were generally lower in the wildflowers, although the highest single detection was from wildflower pollen. By also collecting and analyzing the pollen gathered by foraging bees, the authors further concluded that the contamination from both wildflowers and the crop contributed to bee exposures.
Forister, M. L., B. Cousens, J. G. Harrison, K. Anderson, J. H. Thorne, D. Waetjen, C. C. Nice, M. D. Parsia, M. L. Hladik, R. Meese, H. van Vliet, and A. M. Shapiro. 2016. Biology Letters. 12:20160475.
Increasing neonicotinoid use and the declining butterfly fauna of lowland California.
This correlational study related the presence or absence of 67 butterfly species at four lowland Northern California sites to the use of five neonicotinoid insecticides as well as the four most widely used non-neonicotinoid insecticides. The study also accounted for summer temperatures and land conversion. In part, the study was undertaken to better understand the dramatic decline in the numbers of butterfly species observed at these sites since the late 1990s.
Researchers found a negative relationship between neonicotinoid use, which began in the region in 1995, and annual variation in butterfly species observations. At the level of individual species, the strongest negative associations with neonicotinoid use were for species that were smaller bodied with fewer generations per year. Land conversion had an equally strong negative association to neonicotinoid use, but was not concomitant with the post-1990s decline in the number of butterfly species.
This study, which is one of a few correlational studies, uses a broad approach to document negative effects of neonicotinoids beyond narrow spatial and temporal windows. This approach provides insights to understand the spillover effects of pesticide use on populations of non-target species as well as indirect effects on insectivorous species such as birds and bats.
Gilburn, A. S., N. Bunnefeld, J. McVean Wilson, M. S. Botham, T. M. Brereton, R. Fox, and D. Goulson. 2015. PeerJ. doi:10.771.17/peerj.1402.
Are neonicotinoid insecticides driving declines of widespread butterflies?
This study, from the United Kingdom, related butterfly population levels from 1984 to 2012 to various factors including summer temperatures, spring rainfall, and neonicotinoid use. The researchers found a strong negative association between increasing neonicotinoid use and the decline of 15 of the 17 resident butterfly species studied. As the butterfly declines were not only in agricultural fields the researcher suggested that these chemicals could be moving off-site with water and transported to surrounding habitats. This study is a correlation study and does not confirm causality. While the association found is very strong, researchers cautioned that neonicotinoids could be a proxy for another factor and that further study was warranted. Of the factors evaluated the only other association, which was positive, was between summer temperatures and butterflies.
Hladik, M. L., M. Vandever, and K. L. Smalling. 2015. Science of the Total Environment. 542:469–477.
Exposure of native bees foraging in an agricultural landscape to current-use pesticides.
The U.S. Geological Survey released the first ever study evaluating pesticide exposures to native bees. The study was conducted in mixed use agricultural areas of Colorado. In total, 18 pesticides, and one pesticide breakdown product, were detected in the 54 samples of wild bees collected. Seventy percent of the bee samples contained pesticides. The most commonly found pesticide was the neonicotinoid thiamethoxam, which is highly toxic to bees. Two other neonicotinoids as well as a variety of other insecticides, fungicides, and herbicides were also commonly found in the bees. Sampling methods precluded collection of dead bees; as such, no exposure levels considered lethal to bees were found. Still, some of the contamination levels found in the bees were high enough to cause sublethal effects. Pesticides were often found jointly in the samples, adding to the potential risk. Forty-eight percent of the samples had two or more pesticides with up to nine pesticides being found in a single sample.
Long, E. Y., and C. H. Krupke. 2016. Nature Communications. doi:10.1038/ncomms116291.
Non-cultivated plants present a season-long route of pesticide exposure for honey bees.
This study found that pollen collected by honey bees in agricultural landscapes were contaminated throughout the growing season with multiple pesticides. Approximately 30 pesticides were found at each of the three sites evaluated (an open meadow, a treated maize field margin, and an untreated maize field margin). The chemical makeup between the sites was similar but residue levels were highest at an agricultural site where treated maize had been planted. The pesticides that were ranked as high risk (when compared to lethal doses) were two pyrethroids used in mosquito abatement and other public health pest management, as well as the neonicotinoids clothianidin and thiamethoxam. These two neonicotinoids still triggered high risk even though the researchers purposefully started the study after coated seeds were planted to exclude the risk from neonicotinoid dust-off caused during planting.
Researchers noted that the toxicity of the pesticides didn’t drive whether there was a high risk. In other words, high toxicity did not always lead to a high risk determination. Researchers also noted that the majority of pollen gathered by the honey bees was from wildflowers (although it is worth noting that the agricultural fields were maize, which is not considered attractive to honey bees).
Mogren, C. L., and J. G. Lundgren. 2016. Scientific Reports. doi:10:1038.srep29608.
Neonicotinoid-contaminated pollinator strips adjacent to cropland reduce honeybee nutritional status.
This study concluded that small areas set aside for pollinator forage within a highly developed agricultural landscape are not sufficiently protected from neonicotinoid contamination when the chemicals are used prophylactically throughout the area. Researchers found that honey bee health was compromised whether their colonies were place in habitat on organic or conventional farms when those farms were within a landscape dominated by conventional agriculture.
Leaf tissue from pollinator strips on organic and conventional farms had similar levels of clothianidin. Bee bread collected from hives at organic farms had lower levels of clothianidin. Still, the levels detected were high enough to harm bee health (as measured by the quantity of glycogen, lipid, and protein in worker bees).
The organic sites were generally 140 m from conventional sites. The range was from 10 m to 380 m. Researchers noted that the distance between clothianidin detections and conventional sites indicates that a pathway other than dust-off is causing the contamination. The authors speculated that water and soil routes warrant more attention.
Xerces staff noted that while honey bees have foraging fidelity, the study design doesn’t appear to control for honey bees foraging outside the designated pollinator habitat. Similar research evaluating effects to solitary native bees with shorter foraging range will further elucidate the potential for bees to be exposed while foraging in designated pollinator habitat.
Sanchez-Bayo, F., D. Goulson, F. Pennacchio, F. Nazzi, K. Goka, and N. Desneux. 2016. Environment International. doi:10.1016/j.envint.2016.01.009.
Are bee diseases linked to pesticides? – A brief review.
The reviewers compiled information on how two key factors in bee decline, disease and pesticides, are interconnected. The review starts with a history of bee diseases and their increasing prevalence. It then provides an overview of existing research related to pesticides and bee diseases. The reviewers concluded that while not all pesticides are linked with bee diseases, both neonicotinoid insecticides and ergosterol inhibiting fungicides significantly contribute to the spread and abundance of honey bee pathogens and parasites. The authors also stated that these same concerns are likely to exist for bumble bees and many other wild insects.
Sgolastra, F., P. Medryzcki, L. Bortolotti, M.T. Renzi, S. Tosi, G. Bogo, D. Teper, C. Porrini, R. Molowny-Horas, and J. Bosch. 2016. Pest Management Science. doi:10.1002/ps.4449.
Synergistic mortality between a neonicotinoid insecticide and an ergosterol-biosynthesis-inhibiting fungicide in three bee species.
The researchers explored synergisms between the neonicotinoid clothianidin and the demethylation inhibitor fungicide propiconazole in three bee species — the European honey bee (Apis mellifera) the buff-tailed bumble bee (Bombus terrestris), and the solitary red mason bee (Osmia bicornis). The three bee species all have different life history traits, which results in exposure to different levels of pesticides in field settings. Authors obtained dose-response curves for clothianidin in each species, and then utilized the oral LD10 both alone and with a non-lethal dose of propiconazole to test for synergistic effects. Propiconazole was administered at 35 mg/mL (7 µg/bee) and clothianidin doses ranged from 2 to 160 mg/L. For the synergism experiments, bees were exposed to four treatments: control, fungicide, neonicotinoid, and combination of the fungicide and neonicotinoid. Osmia bicornis was the most sensitive to clothianidin. Mortality was assessed four hours after the exposure ended, and then every 24 hours for four days. For honey bees, synergistic effects were seen only at 4 and 24 hours and there was high mortality in the controls, which the authors attributed to working with older forager bees. In bumblebees, synergistic effects were seen only 4 hours after exposure. Clothianidin and propiconazole showed synergism at all assessment times for the mason bees. The biochemical mechanism for synergism was likely related to the fungicide inhibiting cytochrome p450-mediated detoxification (essentially halting an insect’s detoxification system). These results suggest the potential for synergism in bees that are exposed to neonicotinoids and fungicides.
Smith, R. G., L. W. Atwood, M. B. Morris, D. A. Mortensen, and R. T. Koidec. 2016. Agriculture, Ecosystems and Environment. 216:269–273.
Evidence for indirect effects of pesticide seed treatments on weed seed banks in maize and soybean.
This study’s findings support the hypothesis that seeds coated with neonicotinoids and fungicides could undermine natural sources of biological weed control.
The study sought to answer whether pesticide seed treatments reduced the abundance of natural enemies (seed predators and pathogens), thus causing larger and less diverse weed seed banks. The results provided some support to this hypothesis. During the two years of study the mean density of germinable weed seeds were 40% and 32% greater in the site where coated seed was planted compared to the control (not statistically significant). Also, the weed seed banks were more diverse both years in the control site. Species richness and evenness of germinable seed bank did not differ between case and control plots. It was interesting to note that while there were no statistically significant difference between the case and control for either weed-seed richness or evenness, the diversity indices (which look at both evenness and richness) did show statistically significant differences. The researchers theorized this is due to subtle but consistent changes in all these parameters. Unfortunately, the researchers did not measure the natural enemy populations.
Stanley, D. A., M. P. Garratt, J. B. Wickens, V. J. Wickens, S. G. Potts, and N. E. Raine. 2015. Nature. doi:10.1038/nature16167.
Neonicotinoid pesticide exposure impairs crop pollination services provided by bumblebees.
This novel research evaluated whether chronic field realistic exposure to a neonicotinoid insecticide (thiamethoxam) affected the pollination service that bumble bees provide in apple orchards. The study found that flowers pollinated by bumble bees exposed to 10 ppb of thiamethoxam produced fruit with significantly fewer seeds (36% less) than those flowers pollinated by bees unexposed to thiamethoxam. The reduced production of seeds indicates reduced pollination services which in turn impacts quality and quantity of fruit production. The researchers found no observable difference in how the individual bees behaved on flowers. However, colonies exposed to the neonicotinoid had lower visitation rates, and collected pollen less often than control colonies.
Stanley, D.A., K.E. Smith, and N.E. Raine. 2015. Scientific Reports. 5:16508. doi: 10.1038/srep16508.
Bumblebee learning and memory is impaired by chronic exposure to a neonicotinoid pesticide.
This study explores the effects of neonicotinoid insecticides on learning and memory in bumble bees. The authors exposed bumblebees to both acute and chronic field-realistic doses of the neonicotinoid thiamethoxam and tested its effect on bumble bees on learning and memory. Bumblebees were tested for olfactory learning performance by evaluating proboscis extension reflex (PER) conditioning. As part of the acute experiment bumble bees were randomly assigned to a control group, or groups that were exposed to 2.4, 10, or 250 ppb of thiamethoxam; in the chronic exposure experiment, bumble bees were assigned to a control group, or to groups that were exposed to 2.4, or 10 ppb of thiamethoxam for 24 days. Acute exposures were intended to simulate a single bee foraging on multiple flowers from a treated crop, and chronic to simulate levels a colony would encounter foraging on a treated crop for 3-4 weeks. Bumble bees were tested for trainability (whether bees learnt the association between odor and reward, or not, over the training period), learning level (how frequently bees showed they had learned the association between odor and reward by extending their proboscis to the trained odor alone), learning speed (the first odor presentation during the training period to which a bee first showed the learned association by proboscis extension), and memory (whether bees remembered the association between odor and reward after a 3-hour break following conditioning).
In the acute exposure experiment, individual bumble bees were fed sugar water containing thiamethoxam and then tested. Bees in the control and 2.4 ppb groups were more trainable than the 250 ppb group, and control bees showed a higher learning level than the 10 and 250 ppb groups. Acute exposure to thiamethoxam did not appear to affect the learning ability or the memory of trainable.
In the chronic exposure experiment, bees were exposed to 2.4 and 10 ppb of thiamethoxam for a period of 24 days. Chronic exposure to thiamethoxam did not appear to affect trainability or learning level, but control groups had a faster learning speed response and better memory retention than treatment groups. . Bees chronically exposed to thiamethoxam (at 2.4 and 10 ppb) took 27-38% more trials to learn than the controls, which could have significant impacts on foraging success and colony performance in the wild. Differences in the rates of learning seen after chronic exposure could mean that exposed bees would need to spend more time re-learning complex flowers or the location of rewarding floral patches. Treated bees (at 2.4 ppb) were less likely to respond to the stimulus after the 3-hour period post-exposure than they were at the end of the trial. The authors recommend that pesticide risk assessments should include chronic and sublethal effects on species beyond honeybees.
The results of this study show that acute exposure to thiamethoxam can affect bumble bee trainability and learning level, and that chronic exposure to thiamethoxam can affect bumble bee learning speed and memory.
Stanley, D.A., A.L. Russell, S.J. Morrison, C. Rogers, and N.E. Raine. 2016. Journal of Applied Ecology. 53:1440-1449.
Investigating the impacts of field-realistic exposure to a neonicotinoid pesticide on bumblebee foraging, homing ability and colony growth.
The authors examined chronic exposure to thiamethoxam and its effect on bumblebee foraging, homing, and corresponding colony growth. RFID tags were used to monitor foraging activity, and the number of bees returning with pollen loads was also recorded. The number of individuals returning with pollen was recorded starting after day 5 of treatments, and homing trials began after 2 weeks of treatment. Exposure to thiamethoxam had no effect on the number of days that bees foraged, the daily number of foraging trips, or the number of bees foraging per colony. However, bumble bees exposed to thiamethoxam did perform significantly longer foraging trips compared to controls (68 vs. 55 min), and returned with pollen less frequently.
In the homing trials, control bees and bees exposed to thiamethoxam were released at 1 km or 2 km distances; researchers recorded the return rate and return time of individual bees. Interestingly, exposed bees had a better return rate than controls at both 1 km and 2 km distances. For the 1 km trials, the volume of sucrose consumed before the trial also contributed to return rate, and return time was best explained by nectar consumption only. The authors provide several theories for the positive effect of thiamethoxam exposure on homing ability: neonicotinoids could excite brain regions involved with navigation, the longer foraging trips of exposed bees could have included more time exploring the landscape than foraging, and potential selective impacts of exposure could leave the most fit individuals to survive through the trial. They also note that temperature and solar radiation can impact homing, and it would be interesting to test for interactive effects with pesticide exposure (Stanley et al. 2016).
While the researchers did not see significant effects on colony growth from treatment, the large confidence intervals suggested that larger sample sizes may be needed to fully address this question; on average the number of bees in control colonies were greater than the number of bees in treatment colonies – though this difference was not statistically significant. Notably this study did not measure the effect of thiamethoxam on the number of reproductive bumble bees (queens and males).
Overall, thiamethoxam exposure made the bumblebees less efficient pollen foragers over their entire foraging career, suggesting that impacts to pollination services could be exacerbated over time. The effects documented in this study were seen at very low exposures (2.4 ppb) while bees also had access to uncontaminated nectar in the field. This suggests that very low levels of thiamethoxam exposure can negatively affect bumble bees.
Straub et al. 2016. Proceedings of the Royal Society of Biology. 283:20160506. doi: 10.1098/rspb.2016.0506.
Neonicotinoid insecticides can serve as inadvertent insect contraceptives.
The researchers examined the effects of two neonicotionoids, thiamethoxam and clothianidin, on male honeybees’ reproductive capacity. Twenty honeybee colonies were established and treated colonies were fed pollen paste containing either 4.5 ppb thiamethoxam or 1.5 ppb clothianidin for 50 days. Once the males emerged, they were examined for abnormalities and the presence of Varroa destructor. Workers and drones were collected from each colony for a total of six hoarding cages of bees (10 drones and 20 workers) per colony. Drones were removed from randomly selected cages (three per colony) once they reached sexual maturity for sperm quantity and viability (proportion of sperm alive) assessments. The researchers found no significant difference in drone body mass between treatment and control groups. However, the median longevity of treated drones was significantly lower than controls with close to 50% difference in survival rates. Sperm quantity in drones was not significantly different, but sperm viability was significantly lower in treatment groups. There were on average approximately 39% less living sperm in treatment groups compared to controls. Declines in drone longevity and sperm viability can affect the success of colonies and the genetic variation within them (Straub et al. 2016). While this research study is not directly related to bumble bees, it indicates that neonicotinoid insecticides, in addition to having lethal and sublethal effects on bees, may be affecting reproductive capacity of males.
Thompson, H. 2015. Integrated Environmental Assessment and Management. doi: 10.1002/ieam.1737.
Extrapolation of acute toxicity across bee species.
This study attempts to determine drivers in sensitivity differences between bee species with a goal of supporting development of higher tier risk assessment and testing strategies.
Thompson, H., M. Coulson, N. Ruddle, S. Wilkins, P. Harrington, S. Harkin. 2016. Pest Management Science. doi: 10.1002/ps.4202.
Monitoring the effects of thiamethoxam applied as a seed treatment to winter oilseed rape on the development of bumblebee (Bombus terrestris) colonies.
Researchers compared bumble bee colonies located in oilseed rape fields planted with thiamethoxam coated seed to bumble bee colonies located in oilseed rape fields grown with untreated seed. The researchers reported that there were no detectable adverse effects on the bumble bee colonies located in oilseed rape fields planted with seed coated with thiamethoxam.
While the results of this study are not to be dismissed, we question whether the extent of the study is sufficient to fully understand impact to bumble bee colonies. Notably, in Figure 2 and Figure 3 of the paper there is a notable increase in activity for both control groups at the end of the season, while this increase in activity is largely absent in the treatment group (transition between week 4 and 5). The treatment groups switch from being the most active colonies in week 4 to the least active colonies in week 5. Since the end of the season is essential for producing viable reproductive members, we question if this may have produced a discernable outcome in colony growth had the experiments continued. This difference was not noted in the text.
It is also notable that this study does not consider the effects of exposure to bumble bee colonies during the essential colony foundation period. As queens search for, and establish, nest sites they are highly susceptible to environmental perturbations. Dust from the planting of coated seed could potentially be released during the time when colonies are being established (see Krupke et al. 2012, Tapparo et al. 2012 ). There is little question that exposure to neonicotinoids during this foundation period, and continued exposure after the crop bloom period, could have profound effects on colony development and is in need of further exploration. The potential effects from exposure to dust from planting is not discussed or considered in the text.
Traynor, K.S., J.S. Pettis, D.R. Tarpy, C.A. Mullin, J.L. Frazier, M. Frazier, and D. vanEngelsdorp. 2016. Scientific Reports. doi: 10.1038/srep33207.
In-hive Pesticide Exposome: Assessing risks to migratory honey bees from in-hive pesticide contamination in the Eastern United States.
This study evaluated pesticide exposure and risk to honey bees in different crop systems along the eastern seaboard. The researchers identified a total of 93 pesticide residues in their samples (13 in bees, 61 in beebread, and 70 in wax). Notably the researchers found that mortality increased with the total number of products found in honey bee wax, indicating that repeated and compounding effects from several chemicals throughout the season may be significant.
This study also found that fungicides with certain modes of action (B.Cyto-Cytoskeleton and motor proteins; C.Resp–Respiration, G.Sterol-Sterol biosynthesis in membranes, M.Multi-Multi-site contact activity) were significantly elevated in colonies that died during the summer season.
Walters, K.F.A. 2016. Insect Conservation and Diversity. doi: 10.11111/icad.12177.
Neonicotinoids, bees and opportunity costs for conservation.
This article attempts to broaden the debate of neonicotinoid role in pollinator decline by taking into account the full range of issues related to pollinator decline, and considering the consequences of regulation on modern agricultural systems.
Woodcock, B. A., N. J. B. Isaac, J. M. Bullock, D. B. Roy, D. G. Garthwaite, A. Crowe and R. F. Pywell. 2016. Nature Communications. doi:10.1038/ncomms12459.
Impacts of neonicotinoid use on long-term population changes in wild bees in England.
This study tested whether commercial use of neonicotinoids on oilseed rape (OSR) crops in England can be linked with bee declines in the wild at a national scale. Laboratory and field tests have demonstrated both lethal and sublethal effects from neonicotinoid exposures. Yet, these studies are unable to determine whether neonicotinoids are linked to bee declines at timescales relevant to population level processes.
Using 18 years of information from a wild bee distribution dataset and relating it to pesticide use survey data, this correlational study was the first to evaluate the long-term impact on wild bee populations from neonicotinoid use in OSR. The researchers found evidence that sublethal impacts of neonicotinoid exposure is linked to large-scale population extinctions for wild bees in England. More specifically, the study demonstrated that exposure to neonicotinoids from use of coated OSR seeds can impact the population persistence of wild bee communities. Still, the reductions have not led to population extinctions on a national scale.
The effects of neonicotinoids are strongest for, but not limited to, species known to forage on OSR. The negative association was 3 times greater for the species that foraged on OSR compared to bee species not known to forage on OSR. The researchers also found a positive association between OSR cover with the distribution of OSR foraging bees. Yet, the benefits of OSR cover do not compensate for the negative effects of neonicotinoid exposure.
Researchers also evaluated the impact of foliar applications of insecticides. Foliar applications of insecticides, including neonicotinoids, had little or no negative consequences on the persistence of wild bee populations. It was hypothesized that the lack of a correlation could be due to management decisions that minimize exposure during foliar applications.
While not studied, the findings suggest that other mass flowering crops (e.g., sunflowers) could similarly provide a route of exposure to neonicotinoids, thus negatively impacting wild bee population persistence. Finally, researchers point out the need for further study on the capacity of bees to recover from the effects of neonicotinoid exposure.
Further information is available in an article on the blog of the Centre for Ecology and Hydrology, at: http://www.ceh.ac.uk/news-and-media/blogs/wild-bees-neonicotinoids-defining-decline.
Woodcock, B.A., M.S. Heard, M.S. Jitlal, M. Rundlof, James M. Bullock, R.F. Shore and R.F. Pywell. 2016. Journal of Applied Ecology. doi: 10.1111/1365-2664.12676.
Replication, effect sizes and identifying the biological impacts of pesticides on bees under field conditions.
This article evaluates the European Food Safety Authority’s current risk assessment processes. The authors suggest that to more accurately assess risk (thus minimizing risks to the environment) pesticide risk assessment may need to include field trials of greater than 1 year of exposure to species and populations. Authors argued that such field trials provide key validation under real-world conditions.
Wu-Smart, J. and M. Spivak. 2016. Scientific Reports. doi: 10.1038/srep32108.
Sub-lethal effects of dietary neonicotinoid insecticide exposure on honey bee queen fecundity and colony development.
Researchers undertook this study to expand understanding of the effects imidacloprid has on honey bee queens. They found adverse effects to the queen’s egg laying and locomotor skills at the lowest dose (10 ppb). Some of the effects were less evident as colony size increased. Thus researchers concluded that larger colony sizes may act as a buffer to pesticide exposure (Wu-Smart & Spivak 2016).