Jeff Pettis

Colony losses, managed colony population decline, and Colony Collapse Disorder in the United States

Apis mellifera, CCD, Colony Collapse Disorder, Israeli acute paralysis virus, Nosema ceranae, pesticides, Varroa destructor, nutrition, stress Journal of Apicultural Research 49(1): 134-136 (2010)

Morphological, molecular, and phylogenetic characterization of Nosema ceranae, a microsporidian parasite isolated from the European honey bee, Apis mellifera.

ABSTRACT. Nosema ceranae, a microsporidian parasite originally described from Apis cerana, has been found to infect Apis melllifera and is highly pathogenic to its new host. In the present study, data on the ultrastructure of N. ceranae, presence of N. ceranae‐specific nucleic acid in host tissues, and phylogenetic relationships with other microsporidia species are described. The ultrastructural features indicate that N. ceranae possesses all of the characteristics of the genus Nosema. Spores of N. ceranae measured approximately 4.4 × 2.2 μm on fresh smears. The number of coils of the polar filament inside spores was 18–21. Polymerase chain reaction (PCR) signals specific for N. ceranae were detected not only in the primary infection site, the midgut, but also in the tissues of hypopharyngeal glands, salivary glands, Malpighian tubules, and fat body. The detection rate and intensity of PCR signals in the fat body were relatively low compared with other examined tissues. Maximum parsimony analysis of the small subunit rRNA gene sequences showed that N. ceranae appeared to be more closely related to the wasp parasite, Nosema vespula, than to N. apis, a parasite infecting the same host.

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.

Genomic survey of the ectoparasitic mite Varroa destructor, a major pest of the honey bee Apis mellifera

BackgroundThe ectoparasitic mite Varroa destructor has emerged as the primary pest of domestic honey bees (Apis mellifera). Here we present an initial survey of the V. destructor genome carried out to advance our understanding of Varroa biology and to identify new avenues for mite control. This sequence survey provides immediate resources for molecular and population-genetic analyses of Varroa-Apis interactions and defines the challenges ahead for a comprehensive Varroa genome project.ResultsThe genome size was estimated by flow cytometry to be 565 Mbp, larger than most sequenced insects but modest relative to some other Acari. Genomic DNA pooled from ~1,000 mites was sequenced to 4.3× coverage with 454 pyrosequencing. The 2.4 Gbp of sequencing reads were assembled into 184,094 contigs with an N50 of 2,262 bp, totaling 294 Mbp of sequence after filtering. Genic sequences with homology to other eukaryotic genomes were identified on 13,031 of these contigs, totaling 31.3 Mbp. Alignment of protein sequence blocks conserved among V. destructor and four other arthropod genomes indicated a higher level of sequence divergence within this mite lineage relative to the tick Ixodes scapularis. A number of microbes potentially associated with V. destructor were identified in the sequence survey, including ~300 Kbp of sequence deriving from one or more bacterial species of the Actinomycetales. The presence of this bacterium was confirmed in individual mites by PCR assay, but varied significantly by age and sex of mites. Fragments of a novel virus related to the Baculoviridae were also identified in the survey. The rate of single nucleotide polymorphisms (SNPs) in the pooled mites was estimated to be 6.2 × 10-5per bp, a low rate consistent with the historical demography and life history of the species.ConclusionsThis survey has provided general tools for the research community and novel directions for investigating the biology and control of Varroa mites. Ongoing development of Varroa genomic resources will be a boon for comparative genomics of under-represented arthropods, and will further enhance the honey bee and its associated pathogens as a model system for studying host-pathogen interactions.

Virus infections in Brazilian honey bees

This work describes the first molecular-genetic evidence for viruses in Brazilian honey bee samples. Three different bee viruses, Acute bee paralysis virus (ABPV), Black queen cell virus (BQCV), and Deformed wing virus (DWV) were identified during a screening of RNAs from 1920 individual adult bees collected in a region of southeastern Brazil that has recently shown unusual bee declines. ABPV was detected in 27.1% of colony samples, while BQCV and DWV were found in 37% and 20.3%, respectively. These levels are substantially lower than the frequencies found for these viruses in surveys from other parts of the world. We also developed and validated a multiplex RT-PCR assay for the simultaneous detection of ABPV, BQCV, and DWV in Brazil.

Effects of Bt corn pollen on honey bees: emphasis on protocol development*

Laboratory feeding studies showed no effects on the weight and survival of honey bees feeding on Cry1 Ab-expressing sweet corn pollen for 35 days. In field studies, colonies foraging in sweet corn plots and fed Bt pollen cakes for 28 days showed no adverse effects on bee weight, foraging activity, and colony performance. Brood development was not affected by exposure to Bt pollen but significantly reduced by the positive insecticide control. The number of foragers returning with pollen loads, pollen load weight, and forager weight were the most consistent endpoints as indicators of foraging activity. Using variances of measured endpoints, experimental designs required to detect a range of effect sizes at 80% statistical power were determined. Discussed are methods to ensure exposure to pollen, duration of exposure, positive controls, and appropriate endpoints to consider in planning laboratory and field studies to evaluate the non-target effects of transgenic pollen.ZusammenfassungDer Kontakt mit Pollen von CryIAb-exprimierenden Maispflanzen, die Gene des Bodenbakteriums Bacillus thuringiensis (Bt) enthalten, kann direkte oder indirekte Auswirkungen auf Honigbienen haben. Wir führten Labor- und Feldstudien durch, um mögliche Effekte von Pollen von Bt-Süssmais auf verschiedene Indikatoren der Fitness und Volksleistung von Honigbienen zu erfassen. Die Laborstudien Hessen keine Effekte auf das Lebendgewicht und die Überlebensraten von Bienen erkennen, die Bt-Pollen aufgenommen hatten (Abb. 1, 2). Der Zusatz von Honig erhöhte die Aufnahme von Pollen unter Laborbedingungen. Auch in den Feldstudien war weder nach Aufnahme von Pollen in Bt-Süssmaisparzellen noch nach Verzehr von Bt-Pollenkuchen über 28 Tage hinweg eine negative Auswirkung auf das Gewicht der Bienen, ihr Sammelverhalten oder auf die Kolonieleistung zu erkennen. Die beständigsten Endpunktindikatoren für das Sammelverhalten waren der Prozentsatz der mit Pollenhöschen zurückkehrenden Sammlerinnnen, das Gewicht der Pollenhöschen und das Gewicht der Sammlerinnen. Eine Reduktion in diesen Endpunkten um 40 % im Vergleich zu den Kontrollen hätte bei den in dieser Feldstudien zugrundegelegten Wiederholungen mit einer Wahrscheinlichkeit von 80 % erkennbar sein müssen (Abb. 3). Die Völksgrösse und die Messungen der Pollen- und Honigvorräte waren hingegen mit ziemlichen Schwankungen verbunden und lieferten weniger verlässliche Indikatoren für die Völksleistung. Unter den dieser Studie zugrundegelegten Wiederholungen wären nur Unterschiede von über 75 % in den entsprechenden Pollen- und Honigvorräten mit einer Wahrscheinlichkeit von 80 % zu erkennen gewesen. Der Kontakt mit Bt-Pollen zeigte keine Effekte auf die Brutentwicklung. Diese war jedoch in den positiven Kontrollen mit Insektizidkontakt (Imidacloprid) signifikant reduziert (Abb. 4). Angesichts der Unterschiede in der Brutnestgrösse sollten Experimente, die die Beurteilung von Auswirkungen auf die Brut zum Ziel haben, mit mindestens vier Völkern in jeder der sechs Replikaparzellen durchgeführt werden, wenn ein Unterschied von 50 % im Vergleich zu Kontrollen erkennbar sein soll (Abb. 5). Wir diskutieren Methoden, die dazu beitragen sollen den Kontakt mit Pollen, die Kontaktdauer, die positiven Kontrollen, sowie die angemessenen Endpunkte abzusichern. Diese sollten für die Planung von Labor- und Feldstudien zu Auswirkungen von transgenem Pollen auf Nicht-Zielorganismen von Nutzen sein.

Association of novel mutations in a sodium channel gene with fluvalinate resistance in the mite, Varroa destructor

SUMMARY Varroa (Varroa destructor) has recently become resistant to Apistan, a pyrethroid pesticide with tau-fluvalinate as its active ingredient. In many insect pests, resistance to pyrethroid insecticides is due to reduced target-site (sodium channel) sensitivity to pyrethroids in the nervous system, a phenomenon called knockdown resistance (kdr). A number of studies showed that kdr and kdr-type resistance is a result of point mutations in the para family of sodium channel genes. To investigate the molecular mechanism of resistance to fluvalinate in varroa, we have cloned and sequenced a large cDNA fragment corresponding to segment 3 of domain II (IIS3) to segment 6 of domain IV (IVS6) of a para-homologous sodium channel gene (VmNa) from susceptible and resistant mite populations. The deduced amino acid sequence from this cDNA shares 71%, 60%, and 50% identity with the corresponding region of the para-homologous protein of the Southern cattle tick, Boophilus microplus, Drosophila melanogaster Para, and rat brain type II sodium channel α-subunit, respectively. Sequence analysis revealed that four amino acid changes, F758L in IIIS6, L826P in the linker connecting domains III and IV, I982V in IVS5 and M1055I in IVS6, were correlated with fluvalinate resistance in both Florida and Michigan populations. Interestingly, the kdr or super-kdr (which confers much higher level resistance than kdr) mutation previously identified in insects was not detected in the resistant mites. These results support the emerging notion that distinct sodium channel gene mutations are selected in different insects and arachnids in response to pyrethroid selection.

Comparisons of pollen substitute diets for honey bees : consumption rates by colonies and effects on brood and adult populations

Summary Commercially available pollen substitute diets for honey bees (Apis mellifera L.) were evaluated for consumption and colony growth (brood and adult populations) and compared with pollen cake and high fructose corn syrup (HFCS). Two trials were conducted; the first for 3 months during the fall and winter and a second for 2 months in the summer. Three diets were tested in Trial 1 (Diet-1, Diet-2, and Diet-3 (liquid and patty form)) and Diet-2 and Diet-3 (patty) in Trial 2. In both Trials, Diet-2 and Diet-3 patty were consumed at rates that were comparable to pollen cake. Colonies consumed significantly less Diet-1 than the other diets. There was a significant relationship between the amount of diet consumed and the change in brood area and adult population size in both Trials. Colonies fed Diet-3 patty produced significantly more brood than those fed pollen cake or any other diet in Trial 1. The lowest brood production occurred in colonies fed Diet-1 or HFCS. Adult populations in colonies fed Diet-3 liquid or patty did not differ from those fed pollen cake, and were significantly larger than colonies fed Diet-1 or Diet-2. In Trial 1, when some pollen was being collected by colonies, Diet-2 and Diet-3 did not differ from pollen cake in brood or adult population growth.

Standard methods for small hive beetle research

Summary Small hive beetles, Aethina tumida, are parasites and scavengers of honey bee and other social bee colonies native to sub-Saharan Africa, where they are a minor pest only. In contrast, the beetles can be harmful parasites of European honey bee subspecies. Very rapidly after A. tumida established populations outside of its endemic range, the devastating effect of this beetle under suitable climatic conditions prompted an active research effort to better understand and control this invasive species. Over a decade, A. tumida has spread almost over the entire USA and across the east coast of Australia. Although comparatively few researchers have worked with this organism, a diversity of research methods emerged using sets of diverse techniques to achieve the same goal. The diversity of methods made the results difficult to compare, thus hindering our understanding of this parasite. Here, we provide easy-to-use protocols for the collection, identification, diagnosis, rearing, and for experimental essays of A. tumida. We hope that these methods will be embraced as standards by the community when designing and performing research on A. tumida.

Linking measures of colony and individual honey bee health to survival among apiaries exposed to varying agricultural land use

We previously characterized and quantified the influence of land use on survival and productivity of colonies positioned in six apiaries and found that colonies in apiaries surrounded by more land in uncultivated forage experienced greater annual survival, and generally more honey production. Here, detailed metrics of honey bee health were assessed over three years in colonies positioned in the same six apiaries. The colonies were located in North Dakota during the summer months and were transported to California for almond pollination every winter. Our aim was to identify relationships among measures of colony and individual bee health that impacted and predicted overwintering survival of colonies. We tested the hypothesis that colonies in apiaries surrounded by more favorable land use conditions would experience improved health. We modeled colony and individual bee health indices at a critical time point (autumn, prior to overwintering) and related them to eventual spring survival for California almond pollination. Colony measures that predicted overwintering apiary survival included the amount of pollen collected, brood production, and Varroa destructor mite levels. At the individual bee level, expression of vitellogenin, defensin1, and lysozyme2 were important markers of overwinter survival. This study is a novel first step toward identifying pertinent physiological responses in honey bees that result from their positioning near varying landscape features in intensive agricultural environments.