Does hive strength predispose honey bees to European foulbrood disease?

BC Blueberries, Project Apis m., Boehringer Ingelheim, Mitacs, Costco Wholesale, Saskatchewan Agriculture Development Fund, Agriculture Funding Consortium, Saskatchewan Beekeepers Development CommissionEuropean Foulbrood (EFB) is a bacterial disease of young honey bee larvae, caused by Melissococcus plutonius infection of the larval midgut. It occurs in times of nutritional stress when insufficient food is supplied to the larvae by the nursing bee population. EFB increases larval mortality, thereby limiting the colony’s growth, which can have consequences on the hive’s pollination services, honey production, and ability to reproduce. Recently, increased incidence of EFB has been observed across North America; however, the underlaying factors predisposing colonies to EFB remain largely unknown

Are honey bees a suitable model for fetal alcohol spectrum disorders?

Fetal alcohol spectrum disorders (FASDs) are a continuum of disorders caused by prenatal exposure to ethanol. They affect an estimated 4% of Canadians. FASDs are associated with a host of complications including, but not limited to, cognitive difficulties, developmental delay, increased mortality, smaller birth weight, smaller brain size, as well as gross and fine motor issues. It has been previously established that fruit flies (Drosophila melanogaster) are a suitable invertebrate model for FASDs. Honey bees (Apis mellifera) share many similarities to Drosophila as a research model, but with the distinct advantage of highly social behaviour, similar to that of humans. In this project we exposed honey bees to incremental, sublethal concentrations of ethanol during larval development and monitored their survival, developmental rate, and weight at adult emergence. We found that larval honey bees exposed to ≥6% ethanol experienced significantly higher mortality, developmental delay, and lower body weight at emergence. Accordingly, these results, in combination with ongoing neurobehavioural analyses of adult bees exposed to ethanol as larvae, suggest that honey bees may be an ideal model for human FASDs

Evaluation of Natural Antagonists for Biological Control of Drosophila suzukii

The polyphagous insect Drosophila suzukii (eponymous: spotted wing drosophila, SWD) is indigenous to Southeast Asia and has been spreading rapidly in North American and European countries since 2008. It became primarily a pest insect of berries, grapes and stone fruits as it lays eggs in ripening fruits leading to rapid fruit collapse and causing high economic losses. Because of its life cycle, chemical control of SWD is very complicated and often impossible. Hence, the evaluation and development of biological control measures are of great importance for conventional and organic fruit growers. As a first approach (Chapter II), biological control agents (BCA) that are already available for Diptera have been tested for their efficacy against SWD. For this purpose, various products of the gram-positive subspecies Bacillus thuringiensis serovar. israelensis (B.t.i.), which is specific for the Diptera, such as mosquitos and blackflies, were applied to SWD larvae and adults. It could be demonstrated in laboratory experiments, that the examined products showed neither an increased mortality after exposure to SWD larvae or adults nor a repellent effect on the oviposition behaviour after application to host fruits. Thus, B.t.i. products could be excluded as possible candidates for SWD control. As shown in Chapter III, Neem oil, an extract from the seeds of the Neem tree Azadirachta indica, was also inefficient against SWD. The extract is mainly applied to larvae of leaf-sucking insects, on which the active ingredient Azadirachtin A has a lethal effect and inhibits ecdysis (moulting). These effects also appeared on SWD larvae, but only at concentrations ten times higher than suggested for target organisms. In addition, no repellent effect to SWD was noted. Another approach to find host-specific antagonists suitable as BCA is to examine natural populations for pathogens that are already associated to the respective species. In Chapter IV, such a pathogen belonging to the phylum Microsporidia is described. Based on comprehensive light and electron microscopic studies as well as molecular analysis of rDNA sequences and phylogenetic studies revealed a new microsporidian species, which was eventually named Tubulinosema suzukii sp. nov. T. suzukii was further tested for its competence as an antagonist of SWD (Chapter V). The median lethal spore concentration (LC50: 6900 spores/μl) and concentration-dependent mortality after exposure of larvae showed moderate to high virulence of T. suzukii to early developmental stages of SWD. Molecular examination of the infection process via RT-qPCR showed that replication of T. suzukii increased especially during the larval and pupal stages of SWD. This resulted in restricted or delayed development of adult SWD. In addition, population-reducing effects were evaluated by experiments on survival rates and on the ability to lay eggs (oviposition). After inoculation of SWD larvae with T. suzukii, hatching rates were significantly reduced (over 70%), and the survival rates of hatched adult flies as well as their reproductive ability (up to 70% less progeny) were severely impaired. These effects were less pronounced when adult SWD were exposed to T. suzukii. Considering the clear effects on viability and egg deposition as well as generally chronic and sublethal impact of microsporidia on its infected hosts, a long-term effect of T. suzukii infection affecting SWD populations seems to be likely. The results of this thesis indicate that application of B.t.i. products or Neem oil do not offer sufficient control options for SWD since they are either ineffective or would require an excessive and therefore uneconomical application rate. On the other hand, a new microsporidian species, T. suzukii, was isolated and characterized. It showed highly promising effects on larval stages of SWD and its finding encourages further evaluations in semi-field trials

Fall Treatment with Fumagillin Contributes to an Overwinter Shift in <i>Vairimorpha</i> Species Prevalence in Honey Bee Colonies in Western Canada

(1) Background: Microsporidiosis (nosemosis) is an intestinal disorder of adult honey bees caused by the microsporidian pathogens Vairimorpha apis and Vairimorpha ceranae. In Canada, fumagillin is an approved antibiotic used to treat this disease. However, the recommended dosage is based on efficacy studies for V. apis, the native pathogen in European honey bees. Since the detection of V. ceranae in Apis mellifera, V. ceranae became more prevalent in managed European honey bees and seems to have replaced V. apis due to yet unknown reasons. (2) Methods: This colony study investigated the efficacy of fumagillin administered in the fall to colonies infected with both V. apis and V. ceranae and its effects on the Vairimorpha species’ prevalence overwinter. Spore loads in control and fumagillin-treated colonies were analysed by microscopy; Vairimorpha species prevalence was determined molecularly and infection and treatment effects on colony productivity were assessed. (3) Results: Fall fumagillin treatment was associated with a temporary reduction in spore load, but there was no difference in spore loads between treated and control colonies the following spring. Interestingly, fumagillin-treated colonies had a significantly greater prevalence of V. ceranae relative to V. apis the following spring, suggesting fumagillin is less effective in controlling V. ceranae

Table_1_Are fungicides a driver of European foulbrood disease in honey bee colonies pollinating blueberries?.XLSX

IntroductionBlueberry producers in Canada depend heavily on pollination services provided by honey bees (Apis mellifera L.). Anecdotal reports indicate an increased incidence of European foulbrood (EFB), a bacterial disease caused by Melissococcus plutonius, is compromising pollination services and colony health. Fungicidal products are commonly used in blueberry production to prevent fungal diseases such as anthracnose and botrytis fruit rot. Pesticide exposure has been implicated in honey bee immunosuppression; however, the effects of commercial fungicidal products, commonly used during blueberry pollination, on honey bee larval susceptibility to EFB have not been investigated.MethodsUsing an in vitro infection model of EFB, we infected first instar honey bee larvae with M. plutonius 2019 BC1, a strain isolated from an EFB outbreak in British Columbia, Canada, and chronically exposed larvae to environmentally relevant concentrations of fungicide products over 6 days. Survival was monitored until pupation or eclosion.ResultsWe found that larvae chronically exposed to one, two, or three fungicidal products [Supra® Captan 80WDG (Captan), low concentration of Kenja™ 400SC (Kenja), Luna® Tranquility (Luna), and/or Switch® 62.5 WG (Switch)], did not significantly reduce survival from EFB relative to infected controls. When larvae were exposed to four fungicide products concurrently, we observed a significant 24.2% decrease in survival from M. plutonius infection (p = 0.0038). Similarly, higher concentrations of Kenja significantly reduced larval survival by 24.7–33.0% from EFB (p DiscussionThese in vitro results suggest that fungicides may contribute to larval susceptibility and response to M. plutonius infections. Further testing of other pesticide combinations is warranted as well as continued surveillance of pesticide residues in blueberry-pollinating colonies.</p

Image_1_Are fungicides a driver of European foulbrood disease in honey bee colonies pollinating blueberries?.JPEG

IntroductionBlueberry producers in Canada depend heavily on pollination services provided by honey bees (Apis mellifera L.). Anecdotal reports indicate an increased incidence of European foulbrood (EFB), a bacterial disease caused by Melissococcus plutonius, is compromising pollination services and colony health. Fungicidal products are commonly used in blueberry production to prevent fungal diseases such as anthracnose and botrytis fruit rot. Pesticide exposure has been implicated in honey bee immunosuppression; however, the effects of commercial fungicidal products, commonly used during blueberry pollination, on honey bee larval susceptibility to EFB have not been investigated.MethodsUsing an in vitro infection model of EFB, we infected first instar honey bee larvae with M. plutonius 2019 BC1, a strain isolated from an EFB outbreak in British Columbia, Canada, and chronically exposed larvae to environmentally relevant concentrations of fungicide products over 6 days. Survival was monitored until pupation or eclosion.ResultsWe found that larvae chronically exposed to one, two, or three fungicidal products [Supra® Captan 80WDG (Captan), low concentration of Kenja™ 400SC (Kenja), Luna® Tranquility (Luna), and/or Switch® 62.5 WG (Switch)], did not significantly reduce survival from EFB relative to infected controls. When larvae were exposed to four fungicide products concurrently, we observed a significant 24.2% decrease in survival from M. plutonius infection (p = 0.0038). Similarly, higher concentrations of Kenja significantly reduced larval survival by 24.7–33.0% from EFB (p DiscussionThese in vitro results suggest that fungicides may contribute to larval susceptibility and response to M. plutonius infections. Further testing of other pesticide combinations is warranted as well as continued surveillance of pesticide residues in blueberry-pollinating colonies.</p

Image_2_Are fungicides a driver of European foulbrood disease in honey bee colonies pollinating blueberries?.TIF

IntroductionBlueberry producers in Canada depend heavily on pollination services provided by honey bees (Apis mellifera L.). Anecdotal reports indicate an increased incidence of European foulbrood (EFB), a bacterial disease caused by Melissococcus plutonius, is compromising pollination services and colony health. Fungicidal products are commonly used in blueberry production to prevent fungal diseases such as anthracnose and botrytis fruit rot. Pesticide exposure has been implicated in honey bee immunosuppression; however, the effects of commercial fungicidal products, commonly used during blueberry pollination, on honey bee larval susceptibility to EFB have not been investigated.MethodsUsing an in vitro infection model of EFB, we infected first instar honey bee larvae with M. plutonius 2019 BC1, a strain isolated from an EFB outbreak in British Columbia, Canada, and chronically exposed larvae to environmentally relevant concentrations of fungicide products over 6 days. Survival was monitored until pupation or eclosion.ResultsWe found that larvae chronically exposed to one, two, or three fungicidal products [Supra® Captan 80WDG (Captan), low concentration of Kenja™ 400SC (Kenja), Luna® Tranquility (Luna), and/or Switch® 62.5 WG (Switch)], did not significantly reduce survival from EFB relative to infected controls. When larvae were exposed to four fungicide products concurrently, we observed a significant 24.2% decrease in survival from M. plutonius infection (p = 0.0038). Similarly, higher concentrations of Kenja significantly reduced larval survival by 24.7–33.0% from EFB (p DiscussionThese in vitro results suggest that fungicides may contribute to larval susceptibility and response to M. plutonius infections. Further testing of other pesticide combinations is warranted as well as continued surveillance of pesticide residues in blueberry-pollinating colonies.</p