RECENT HONEYBEE SCIENTIFIC PUBLICATIONS By the SNGTV* Honeybee Commission & other contributors Number 6 – March, 2020

Number – main topic that can motivate you to read the article
(First author et al ; Year ; Scientific Journal ; Impact Factor)
1- Control strategies for Varroa jacobsoni and Tropilaelaps mercedeseae: the
example of Pupua New Guinea
(Roberts et al 2020 ; Experimental and Applied Acarology ; IF 1.76)
2- Carriage of pathogen agents in Varroa-free territories: the example of
Australia (Brettell et al 2020 ; Journal of Invertebrate Pathology ; IF 2.10)
3- Effect of wind on foraging behaviour
(Hennessy et al 2020 ; Animal Behaviour ; IF 2.67)
4- Infrared thermography could help in the detection of nests of Vespa velutina, the Asian hornet
(Lioy et al 2020 ; Frontiers in Ecology and Evolution ; IF 2.71)
5- Role of probiotics to better withstand the exposure to pesticides?
(Chmiel et al 2020 ; Insect Science ; IF 2.69)
6- A malnourished larva is a larva more susceptible to the infection to
Paenibacillus larvae (Molinié et al 2020 ; Journal of Apicultural Research ; IF 1.75)
7- Glyphosate Herbicide is not harmless on worker larvae when exposed to
chronic exposure at very low dose
(Vázquez et al 2020 ; Environmental Pollution ; IF 5.71)
8- Nosema, with or without pesticide, disrupts the intestinal microbiota
(Paris et al 2020 ; Journal of Invertebrate Pathology ; IF 2.10)
9- An integrated management strategy to reduce cases of American foulbrood
(Locke et al 2019 ; Preventive Veterinary Medicine ; IF 2.30)
10- Propolis would be effective in reducing the carriage of Nosema ceranae
spores (Mura et al 2020 ; Insect ; IF 2.14)
International Press Review by SNGTV Honeybee commission 2
1- Control strategies for Varroa jacobsoni and Tropilaelaps mercedeseae: the example of
Pupua New Guinea
Roberts, J.M.K., Schouten, C.N., Sengere, R.W., Jave, J., Lloyd, D., 2020. Effectiveness of control strategies for Varroa jacobsoni and Tropilaelaps
mercedesae in Papua New Guinea. Experimental and Applied Acarology.
Abstract: Apiculture in the Pacific island country of Papua New Guinea (PNG) is under significant
pressure from emerging parasitic mites, Varroa jacobsoni and Tropilaelaps mercedesae. Although
numerous mite control products exist, beekeepers in PNG have limited resources and access to
these products and their effectiveness under local conditions is untested. Here we determined
the effectiveness of two brood manipulation strategies—queen caging and queen removal—for
managing V. jacobsoni and T. mercedesae in comparison to the chemical miticide Bayvarol®. Our
results found Bayvarol was the most effective control strategy for V. jacobsoni, maintaining high
efficacy (> 90%) over 4 months with significantly reduced levels of V. jacobsoni compared to
untreated control hives. In contrast, T. mercedesae were significantly reduced by the brood
manipulation strategies over 2 months, but not significantly by Bayvarol compared to the
controls. These results highlight that a combination of strategies is likely needed to effectively
manage both mite pests in PNG. We discuss how these findings are relevant to informing best
practice for honey bee biosecurity and how these strategies can be implemented to improve the
effectiveness of mite management for PNG beekeepers.
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2. Carriage of pathogen agents in Varroa-free territories: the example of Australia
Brettell, L.E., Riegler, M., O’Brien, C., Cook, J.M., 2020. Occurrence of honey bee-associated pathogens in Varroa-free pollinator communities.
Journal of Invertebrate Pathology 107344.
Abstract : Australia remains the last significant land mass free of Varroa, a parasitic mite which
has caused dramatic honey bee (Apis mellifera) colony losses across the globe, due to its
association with the pathogenic deformed wing virus (DWV). As such, Australia continues to
maintain relatively healthy honey bee populations, despite recent work showing apiaries harbor a
surprisingly high prevalence of microbial pathogens. We sought to determine the prevalence of
these microbial pathogens in honey bees and native pollinators actively co-foraging on mass
flowering crops and to understand the extent to which they may be shared between taxa. We
found high prevalences of black queen cell virus (BQCV) and sacbrood virus (SBV) in the honey
bees (88% and 41% respectively), and correspondingly, these were the most common honey bee
pathogens detected in native pollinator taxa, albeit at much lower prevalence; the maximum
prevalence for any pathogen in a native pollinator group was 24% (BQCV in Halictidae spp.).
The viral pathogens Israeli acute paralysis virus and Lake Sinai viruses 1 and 2, and the fungal
parasites Nosema apis and Nosema ceranae, were only rarely detected. Phylogenetic analyses of
the most common pathogens revealed similar strains circulating between species. Our data
suggest that, in Australian orchards, pathogen prevalence in honey bees is a good predictor of
pathogen prevalence in native pollinators, which raises concerns about how the viral landscape
may change in native taxa if, or when, Varroa arrives.
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International Press Review by SNGTV Honeybee commission 3
3. Effect of wind on foraging behaviour
Hennessy, G., Harris, C., Eaton, C., Wright, P., Jackson, E., Goulson, D., Ratnieks, F.F.L.W., 2020. Gone with the wind: effects of wind on honey bee
visit rate and foraging behaviour. Animal Behaviour 161, 23–31.
Abstract: Wind is an important yet understudied environmental influence on foraging behaviour.
We investigated the direct and indirect effects of wind on foraging worker honey bees, Apis
mellifera. Bees were trained to an array of artificial flowers providing nectar rewards in a location
sheltered from natural wind. To examine the direct effect, fans produced four different wind
speeds between 0 and 3 m/s at three different flower spacings: 5 cm (flowers touching) and 10
cm and 20 cm (flowers not touching). To examine the indirect effect of wind moving flowers,
flowers were moved 10 cm at three frequencies between 50 and 110 cycles/min at zero wind
speed. We recorded the number of successful flower visits, time spent flying, search time on a
flower and hesitancy to take off. Bees visited significantly fewer flowers with increasing wind
speed which was caused by a significant increase in hesitancy to take off. This difference in
flower visits between wind speeds was highest at the 20 cm spacing. Flower movement had no
effect on foraging rate; however, there was a significant positive relationship between flower
movement and the total time spent flying. This was counterbalanced by a significant reduction in
time spent searching for the nectary after landing on a flower at the higher flower frequencies.
Our results suggest that it is the direct effect of wind on hesitancy to take off that has the
greatest effect on honey bee foraging rate.
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4. Infrared thermography could help in the detection of nests of Vespa velutina, the Asian
Lioy, S., Bianchi, E., Biglia, A., Bessone, M., Laurino, D., Porporato, M., 2020. Viability of thermal imaging in detecting nests of the invasive hornet
Vespa velutina. Insect Science 1744-7917.12760.
Abstract : Vespa velutina is an invasive hornet species that is colonising Europe, generating
considerable impacts on honey bees, beekeeping and biodiversity. Control and early warning
strategies for this species are mainly based on monitoring plans and procedures of nest detection
and destruction. Technological tools (harmonic radar, radio-telemetry) have been developed to
increase the probabilities of nest detection in new outbreaks. Since hornets are able to regulate
nest temperature, thermography may represent an additional technique that may be used, both
alone or in support to other techniques. In this study, the viability of thermal imaging in detecting
nests of V. velutina was evaluated in controlled conditions. The influence of different
environmental and operative variables (time of the day, presence/absence of leaves covering the
nest, distance between the nest and the operator) were tested on three nests detected during
August 2018 in Italy. All the nests were detectable by thermal imaging, but environmental and
operative variables affect their detectability. The temperature difference between the nests and the
surrounding reaches its maximum before sunrise and without a tree canopy covering the nests.
Although nests were visible in some cases from 30 m, the detectability was higher at shorter
distances, even if this variable may also depend on infrared camera resolution. An increase in the
environmental temperature also generates a decrease of nest detectability. Although some
limitations could occur, these results show the applicability of thermography in detecting V.
velutina nests before the beginning of the reproductive phase, and consequently its potentiality in
control strategies.
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International Press Review by SNGTV Honeybee commission 4
5. Role of probiotics to better withstand the exposure to pesticides?
Chmiel, J.A., Daisley, B.A., Pitek, A.P., Thompson, G.J., Reid, G., 2020. Understanding the Effects of Sublethal Pesticide Exposure on Honey Bees: A
Role for Probiotics as Mediators of Environmental Stress. Frontiers in Ecology and Evolution. 8, 22.
Abstract: Managed populations of the European honey bee (Apis mellifera) support the
production of a global food supply. This important role in modern agriculture has rendered
honey bees vulnerable to the noxious effects of anthropogenic stressors such as pesticides.
Although the deleterious outcomes of lethal pesticide exposure on honey bee health and
performance are apparent, the ominous role of sublethal pesticide exposure is an emerging
concern as well. Here, we use a data harvesting approach to better understand the toxicological
effects of pesticide exposure across the honey bee life cycle. Through compiling adult- and larvalspecific median lethal dose (LD50) values from 93 published data sources, LD50 estimates for
insecticides, herbicides, acaricides, and fungicides are highly variable across studies, especially
for herbicides and fungicides, which are underrepresented in the meta-data set. Alongside major
discrepancies in these reported values, further examination of the compiled data suggested that
LD50 may not be an ideal metric for honey bee risk assessment. We also discuss how sublethal
effects of pesticide exposure, which are not typically measured in LD50 studies, can diminish
honey bee reproduction, immunity, cognition, and overall physiological functioning, leading to
suboptimal honey bee performance and population reduction. In consideration of actionable
solutions to mitigate the effects of sublethal pesticide exposure, we have identified the potential
for probiotic supplementation as a promising strategy that can be easily incorporated alongside
current agricultural infrastructure and apicultural management practices. Probiotic
supplementation is regularly employed in apiculture but the potential for evidence-based
targeted approaches has not yet been fully explored within a formal toxicological context. We
discuss the benefits, practical considerations, and limitations for the use and delivery of
probiotics to hives. Ultimately, by subverting the sublethal effects of pesticides we can help
improve the long-term survival of these critical pollinators.
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6. A malnourished larva is a larva more susceptible to the infection to Paenibacillus larvae
Moliné, M. de la P., Fernández, N.J., Damiani, N., Churio, M.S., Gende, L.B., 2020. The effect of diet on Apis mellifera larval susceptibility to
Paenibacillus larvae. Journal of Apicultural Research 1–8.
Abstract : Honey bees are threatened by changes in food resources. American Foulbrood (AFB),
caused by Paenibacillus larvae, affects Apis mellifera larvae which progressively become more
resistant to the disease with age. It has been suggested that nutritional limitations could result in
increased susceptibility upon exposure to pathogens. This research, conducted on laboratoryreared honey bee larvae, aimed to analyze the effects of diet quality on the susceptibility of Apis
mellifera larvae to P. larvae infections. The values of the lethal dose that killed 50% of the
inoculated larvae (LD50) were determined for five strains of P. larvae (ERIC I). Virulence ranged
from 2 spores/ll for the N15 strain to 906 spores/ll for the Miramar strain. Different groups of
larvae infected with half of the LD50 doses of P. larvae strains were fed Aupinel diet (with daily
increases of glucose, fructose, yeast extract and royal jelly) and four different modifications
thereof. The results show that the absence of a diet component tends to cause an increase in
mortality associated with the infection, depending on the virulence of the strain and the
component suppressed. Glucose and fructose suppression, and mainly royal jelly deprivation,
affect larval susceptibility to AFB and their survival.
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International Press Review by SNGTV Honeybee commission 5
7. Glyphosate Herbicide is not harmless on worker larvae when exposed to chronic exposure
at very low dose
Vázquez, D.E., Latorre-Estivalis, J.M., Ons, S., Farina, W.M., 2020. Chronic exposure to glyphosate induces transcriptional changes in honey bee
larva: A toxicogenomic study. Environmental Pollution 261, 114148.
Abstract: The honey bee Apis mellifera is the most abundant managed pollinator in diverse crops
worldwide. Consequently, it is exposed to a plethora of environmental stressors, among which
are the agrochemicals. In agroecosystems, the herbicide glyphosate (GLY) is one of the most
applied. In laboratory assessments, GLY affects the honey bee larval development by delaying its
moulting, among other negative effects. However, it is still unknown how GLY affects larval
physiology when there are no observable signs of toxicity. We carried out a longitudinal
experimental design using the in vitro rearing procedure. Larvae were fed with food containing
or not a sub-lethal dose of GLY in chronic exposure (120 h). Individuals without observable signs
of toxicity were sampled and their gene expression profile was analyzed with a transcriptomic
approach to compare between treatments. Even though 29% of larvae were asymptomatic in the
exposed group, they showed transcriptional changes in several genes after the GLY chronic
intake. A total of 19 transcripts were found to be differentially expressed in the RNA-Seq
experiment, mainly linked with defensive response and intermediary metabolism processes.
Furthermore, the enriched functional categories in the transcriptome of the exposed
asymptomatic larvae were linked with enzymes with catalytic and redox activity. Our results
suggest an enhanced catabolism and oxidative metabolism in honey bee larvae as a
consequence of the sub-lethal exposure to GLY, even in the absence of observable symptoms.
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8. Nosema, with or without pesticide, disrupts the intestinal microbiota
Paris, L., Peghaire, E., Moné, A., Diogon, M., Debroas, D., Delbac, F., El Alaoui, H., 2020. Honeybee gut microbiota dysbiosis in pesticide/parasite
co-exposures is mainly induced by Nosema ceranae. Journal of Invertebrate Pathology 107348
Abstract : Honeybees ensure a key ecosystem service by pollinating many agricultural crops and
wild plants. However, in the past few decades, managed bee colonies have been declining in
Europe and North America. Researchers have emphasized both parasites and pesticides as the
most important factors. Infection by the parasite Nosema ceranae and exposure to pesticides
can contribute to gut dysbiosis, impacting the honeybee physiology. Here, we examined and
quantified the effects of N. ceranae, the neonicotinoid thiamethoxam, the phenylpyrazole
fipronil and the carboxamide boscalid, alone and in combination, on the honeybee gut
microbiota. Chronic exposures to fipronil and thiamethoxam alone or combined with N. ceranae
infection significantly decreased honeybee survival whereas the fungicide boscalid had no effect
on uninfected bees. Interestingly, increased mortality was observed in N. ceranae-infected bees
after exposure to boscalid, with synergistic negative effects. Regarding gut microbiota
composition, co-exposure to the parasite and each pesticide led to decreased abundance of
Alphaproteobacteria, and increased abundance of Gammaproteobacteria. The parasite also
induced an increase of bacterial alpha-diversity (species richness). Our findings demonstrated
that exposure of honeybees to N. ceranae and/or pesticides play a significant role in colony
health and is associated with the establishment of a dysbiotic gut microbiota.
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International Press Review by SNGTV Honeybee commission 6
9. An integrated management strategy to reduce cases of American foulbrood
Locke, B., Low, M., Forsgren, E., 2019. An integrated management strategy to prevent outbreaks and eliminate infection pressure of American
foulbrood disease in a commercial beekeeping operation. Preventive Veterinary Medicine 167, 48–52.
Abstract: The bacterial disease American Foulbrood (AFB), caused by the Gram-positive
bacterium Paenibacillus larvae, is considered the most contagious and destructive infectious
disease affecting honeybees world-wide. The resilient nature of P. larvae bacterial spores
presents a difficult problem for the control of AFB. Burning clinically symptomatic colonies is
widely considered the only workable strategy to prevent further spread of the disease. Antibiotic
use is banned in EU countries, and although used commonly in the U.S. and Canada, it only
masks symptoms and does not prevent the further spread of the disease. Not surprisingly, there
is an increased demand for chemical-free strategies to prevent and control of AFB. The aim of
this study was to implement a management program with a long-term perspective to reduce
infection pressure and eliminate AFB outbreaks. The study was conducted within a commercial
beekeeping operation in central Sweden that has previously experienced reoccurring AFB
outbreaks. For 5 years, P. larvae were cultured from adult bee samples taken in the fall. The
following spring, any identified sub-clinically infected colonies were shaken onto new material
and quarantined from the rest of the beekeeping operation. After the first year clinical symptoms
were not again observed, and during the 5 years of the study the proportion of apiaries
harbouring P. larvae spores decreased from 74% to 4%. A multinomial regression analysis also
clearly demonstrated that the proportion of infected colonies with the highest levels of spore
counts disproportionately declined so that by the end of the study the only remaining infected
apiaries were in the lowest spore count category (the three higher spore count categories having
been eradicated). These results demonstrate the importance of management practices on AFB
disease epidemiology. Early detection of subclinical spore prevelance and quarantine
management as presented here can provide an effective sustainable chemical-free preventive
solution to reduce both the incidence of AFB outbreaks and continued transmission risk at a
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International Press Review by SNGTV Honeybee commission 7
10. Propolis would be effective in reducing the carriage of Nosema ceranae spores
Mura, A., Pusceddu, M., Theodorou, P., Angioni, A., Floris, I., Paxton, R.J., Satta, A., 2020. Propolis Consumption Reduces Nosema ceranae
Infection of European Honey Bees (Apis mellifera). Insects 11, 124.
Abstract: Nosema ceranae is a widespread obligate intracellular parasite of the ventriculus of
many species of honey bee (Apis), including the Western honey bee Apis mellifera, in which it
may lead to colony death. It can be controlled in A. mellifera by feeding the antibiotic fumagillin
to a colony, though this product is toxic to humans and its use has now been banned in many
countries, so in beekeeping, there exists a need for alternative and safe products effective
against N. ceranae. Honeybees produce propolis from resinous substances collected from plants
and use it to protect their nest from parasites and pathogens; propolis is thought to decrease the
microbial load of the hive. We hypothesized that propolis might also reduce N. ceranae infection
of individual bees and that they might consume propolis as a form of self-medication. To test
these hypotheses, we evaluated the effects of an ethanolic extract of propolis administered
orally on the longevity and spore load of experimentally N. ceranae-infected worker bees and
also tested whether infected bees were more attracted to, and consumed a greater proportion
of, a diet containing propolis in comparison to uninfected bees. Propolis extracts and ethanol
(solvent control) increased the lifespan of N. ceranae-infected bees, but only propolis extract
significantly reduced spore load. Our propolis extract primarily contained derivatives of caffeic
acid, ferulic acid, ellagic acid and quercetin. Choice, scan sampling and food consumption tests
did not reveal any preference of N. ceranae-infected bees for commercial candy containing
propolis. Our research supports the hypothesis that propolis represents an effective and safe
product to control N. ceranae but worker bees seem not to use it to self-medicate when infected
with this pathogen.