Diana Sammataro

Varroa destructor : research avenues towards sustainable control

Summary Pollination by honey bees plays a key role in the functioning of ecosystems and optimisation of agricultural yields. Severe honey bee colony losses worldwide have raised concerns about the sustainability of these pollination services. In many cases, bee mortality appears to be the product of many interacting factors, but there is a growing consensus that the ectoparasitic mite Varroa destructor plays the role of the major predisposing liability. We argue that the fight against this mite should be a priority for future honey bee health research. We highlight the lack of efficient control methods currently available against the parasite and discuss the need for new approaches. Gaps in our knowledge of the biology and epidemiology of the mite are identified and a research road map towards sustainable control is drawn. Innovative and challenging approaches are suggested in order to stimulate research efforts and ensure that honey bees will be able to sustainably fulfil their role in the ecosystem.

The resistance of varroa mites (Acari: Varroidae) to acaricides and the presence of esterase

Abstract Varroa mites (Varroa destructor Anderson and Trueman, 2000) are becoming resistant to acaricide treatments via metabolic and/or target site desensitivity. Results of a survey of mites from the Carl Hayden AZ lab and from cooperators in five locations (Arizona, California, Florida, Maine, North Dakota) showed that some mites were susceptible to all three acaricides (Amitraz, Coumaphos, Fluvalinate) in the spring of 2003, but by fall most mites were resistant. Mites were resistant to all chemicals, even from beekeepers that do not treat colonies with acaricides. We used esterase native activity gels to test for the presence of specific esterases which might be involved in pesticide resistance in varroa. All mites tested had positive bands for esterase, even those exhibiting susceptibility to some acaricides. Based on the differences between the esterase activity gel profile of the susceptible and cross-resistant V. destructor, it is possible that an esterase-mediated resistance mechanism is operative in the population of the mites we analyzed. However, a combination of other resistance mechanisms may be present which make the esterase activity gel method unreliable for use in identifying varroa mites with multiple resistance.

Formation of hydroxymethylfurfural in domestic high-fructose corn syrup and its toxicity to the honey bee (Apis mellifera).

In the United States, high-fructose corn syrup (HFCS) has become a sucrose replacement for honey bees and has widespread use as a sweetener in many processed foods and beverages for human consumption. It is utilized by commercial beekeepers as a food for honey bees for several reasons: to promote brood production, after bees have been moved for commercial pollination, and when field-gathered nectar sources are scarce. Hydroxymethylfurfural (HMF) is a heat-formed contaminant and is the most noted toxin to honey bees. Currently, there are no rapid field tests that would alert beekeepers of dangerous levels of HMF in HFCS or honey. In this study, the initial levels and the rates of formation of HMF at four temperatures were evaluated in U.S.-available HFCS samples. Different HFCS brands were analyzed and compared for acidity and metal ions by inductively coupled plasma mass spectroscopy. Levels of HMF in eight HFCS products were evaluated over 35 days, and the data were fit to polynomial and exponential equations, with excellent correlations. The data can be used by beekeepers to predict HMF formation on storage. Caged bee studies were conducted to evaluate the HMF dose-response effect on bee mortality. Finally, commercial bases such as lime, potash, and caustic soda were added to neutralize hydronium ion in HMF samples, and the rates of HMF formation were compared at 45 degrees C.

Carbohydrate Composition of High-Fructose Corn Syrups (HFCS) Used for Bee Feeding: Effect on Honey Composition

In this study, the carbohydrate composition of high-fructose corn syrups (HFCS) from commercial manufacturers as well as from beekeepers was characterized by GC-MS. Sucrose syrups (SS) were also included in this work for comparison. Fructosyl-fructoses and some unknown carbohydrates, which could correspond to fructosyl-glucoses, have been detected in HFCS for the first time, whereas SS were mainly characterized by the high contents of sucrose. Hydroxymethylfurfural (HMF) content of samples supplied by beekeepers was much more variable; the mean level of HMF was 64.61 ppm (+/-16.92 ppm, 95% CI ranging from 26.91 to 102.31 ppm). Syrups were used to feed caged bees and the resulting honeys produced were analyzed in order to determine their influence in carbohydrate composition. Fructosyl-fructoses were mainly detected in honeys from bees fed with HFCS, but not from those honeys coming from free-flying bees or bees fed with SS.

Mating frequencies of Africanized honey bees in the south western USA

Summary Emerging evidence suggests that there are significant adaptive advantages conferred to genetically diverse honey bee colonies through multiple matings with queens. We determined the intracolony genetic diversity of Africanized honey bee (AHB) colonies from a feral population in the south western USA. A total of 1,253 worker offspring were genotyped from 20 feral colonies (all but three of African mitotype), four managed AHB, three managed European honey bee (EHB), and four control colonies (headed by EHB queens instrumentally inseminated with one, two, five, or ten drones, respectively) using eight microsatellite markers. The 17 feral AHB queens mated with an average of 20.0 ± 6.53 (range 10–32) drones, resulting in effective paternity frequencies of 20.0 ± 8.46 (range 10.56–37.53), which is one of the highest mating numbers recorded within the species. Though Africanized honey bee colonies are among the most genetically diverse Apis mellifera yet recorded, their queen mating frequencies are within the expected range of the species overall, including African honey bees in their native range. The factors responsible for these findings are discussed.

Challenges for developing pathogen-based biopesticides against Varroa destructor (Mesostigmata: Varroidae)

Control of the major pest of apiculture, the ectoparasitic mite Varroa destructor using pathogen-based biopesticides would resolve many of the problems experienced with other forms of control, such as chemical control, hive manipulation, or selection of resistant honeybee strains. Several research groups have developed and tested fungus-based biopesticides in laboratory and field experiments, with varying results. While biopesticides have many desirable qualities, including much lower risk of honey contamination and of pest resistance, future research needs to focus on: (1) identification of the sub-population(s) of V. destructor affected by biopesticides and the duration and impact of the application on mite population dynamics; (2) development of an effective, easily applied formulation, and (3) evaluation of possible side or sublethal effects on bees themselves. Biopesticides need to be evaluated on the field (colony) level in addition to the laboratory level. Researchers should consider providing data that can be easily used to evaluate effect, such as mite drop counts onto sticky boards coupled with assessments of phoretic mite density or brood cell mite density. Exploration for naturally occurring pathogens should be conducted in the native range of V. destructor in Asia.

Comparison of Productivity of Colonies of Honey Bees, Apis mellifera, Supplemented with Sucrose or High Fructose Corn Syrup

Abstract Honey bee colony feeding trials were conducted to determine whether differential effects of carbohydrate feeding (sucrose syrup (SS) vs. high fructose corn syrup, or HFCS) could be measured between colonies fed exclusively on these syrups. In one experiment, there was a significant difference in mean wax production between the treatment groups and a significant interaction between time and treatment for the colonies confined in a flight arena. On average, the colonies supplied with SS built 7916.7 cm2 ± 1015.25 cm2 honeycomb, while the colonies supplied with HFCS built 4571.63 cm2 ± 786.45 cm2. The mean mass of bees supplied with HFCS was 4.65 kg (± 0.97 kg), while those supplied with sucrose had a mean of 8.27 kg (± 1.26). There was no significant difference between treatment groups in terms of brood rearing. Differences in brood production were complicated due to possible nutritional deficiencies experienced by both treatment groups. In the second experiment, colonies supplemented with SS through the winter months at a remote field site exhibited increased spring brood production when compared to colonies fed with HFCS. The differences in adult bee populations were significant, having an overall average of 10.0 ± 1.3 frames of bees fed the sucrose syrup between November 2008 and April 2009, compared to 7.5 ± 1.6 frames of bees fed exclusively on HFCS. For commercial queen beekeepers, feeding the right supplementary carbohydrates could be especially important, given the findings of this study.

An easy dissection technique for finding the tracheal mite, Acarapis woodi (Rennie) (Acari: Tarsonemidae), in honey bees, with video link.

Abstract Since the introduction of varroa mites (Varroa destructor Anderson and Trueman, 2000), the impact of tracheal mites on bees has been largely overshadowed or ignored. Tracheal mites are still present in bees, and may be responsible for some unexplained colony losses. If they cause bee mortality, it is important to be able to identify their presence and at what levels. This paper illustrates a quick and easy technique for dissecting bees for tracheal mites. Hopefully, the video link will be a useful training tool for researchers, beekeepers or regulatory personnel who need to test bees for the mites presence. Tracheal mites are still present in some areas and can be introduced through the sale of bee packages or purchased queens. The presence or absence of these mites can also help determine or eliminate the cause of unexplained colony losses, especially in overwintered colonies.

Feeding essential oils and 2-heptanone in sugar syrup and liquid protein diets to honey bees (Apis mellifera L.) as potential Varroa mite (Varroa destructor) controls

Summary Essential oils were fed to honey bees to determine whether the components were absorbed into bee larvae. The oils were added in either sucrose syrup (origanum and 2-heptanone) or in a liquid protein diet (origanum oil, cinnamon oil, thymol, and 2-heptanone), because sugar and protein sources are differentially utilized in food fed to larvae of different ages. The volatiles emitted by isolated larvae from oil-supplemented colonies were sampled at three different ages (Day 4, Day 6 and Day 9) by Solid Phase Micro-Extraction (SPME) and analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). The only oil volatiles recovered in larvae were the origanum oil components carvacrol and thymol; neither 2-heptanone nor the cinnamon oil components were detected in any larvae. For larvae from colonies fed oil- supplemented sugar syrup, carvacrol volatiles were emitted at higher amounts in younger larvae (Day 4) than in older larvae (Day 9). In contrast, carvacrol and thymol volatiles were detected only in older larvae (Day 6 and Day 9) in colonies reared on oil-supplemented liquid protein diet. Carvacrol was also detected in the cocoons of Day 9 larvae from colonies fed oil-supplemented liquid protein diet, but not oil-supplemented sugar syrup diet. We believe that the age-related differences in oil incorporation by bee larvae reflect the relative importance of supplemental sugars and protein as food sources for bee larvae of these ages. Supplementation in a liquid protein diet represents a more efficacious route for the incorporation of origanum oils in fifth instar bee larvae targeted for invasion by Varroa destructor mites.

The salivary glands of adult female Varroa destructor (Acari: Varroidae), an ectoparasite of the honey bee, Apis mellifera (Hymenoptera: Apidae)

ABSTRACT Varroa destructor Anderson and Trueman 2000, an ectoparasite of honey bees, causes huge economic losses to apiculture annually. Its role as a vector of diseases is thought to involve the salivary glands as the terminal organs of transmission. The salivary glands are paired, oval, non-acinar organs, closely attached to the base of the gnathosoma and enveloped in a sheath of unknown embryological origin. Ultrastructurally, they are characterized by the surrounding sheath, and cells that have a strong presence of rough endoplasmic reticulum, irregular-shaped nuclei, and secretory spheres surrounded by an otherwise electron-lucent cytosol. Secretory spheres are sparse in most peripheral cells and heavily converged about the apical membranes of interior cells. Interior cells are positioned radially about the internal duct cells. The internal ducal lumen is narrow and brush-bordered. The membranes between the ducal lumen and the gland cell cytoplasm are fused and ruptured, allowing the salivary spheres to pass into the interior duct for secretion through the exterior duct. Bacterial biofilms are associated with the spheres and the rupture. Virus particles and endosymbionts are also present in the glands. The external duct remains uncharacterized, but the assumption that its embryonic origin is the same as that of the internal duct and surrounding gland cells is questioned.