Bee Health Research (National Honey Board Production Research)
2006 Research Projects
Environmental and Genetic Traits of Bees that Resist Disease and Increase Productivity
Jay Evans and Jeff Pettis
USDA-ARS Bee Research Laboratory
“Selective screening for honey bee bacterial symbionts that inhibit a key bacterial pathogen, paenibacillus larvae.” Journal of Apicultural Research. 44:168-171.
Abstract
Insects harbor diverse bacterial symbionts and it is increasingly evident that many of these symbionts play important facultative roles as mutualists. While honey bees possess a diverse microbial flora, the impacts of most of these species on honey bee health remains unresolved. Here, in vitro inhibition assays were used to identify bacteria isolated from larval honey bees that inhibit the gram-positive bacterium Paenibacillus larvae larvae, the primary pathogen of bees. Among the diverse bacteria cultured from larval bees, strains placed in the genera Stenotrophomonas, Acitenobacter, Brevibacillus and Bacillus showed the most consistent inhibition of this widespread pathogen. These species were present in approximately 10% of the larvae from an age class that is susceptible to P. l. larvae. Accordingly, symbiotic bacteria including those described here are plausible antagonists toward this important pathogen. The results suggest a tradeoff between the maintenance of potentially beneficial bacterial symbionts versus mechanisms at the individual or colony level to reduce infection by pathogens.“Antagonistic interactions between honey bee bacterial symbionts and implications for disease,” BMC Ecology 6:4
Background
Honey bees, Apis mellifera, face many parasites and pathogens and consequently rely on a diverse set of individual and group-level defenses to prevent disease. One route by which honey bees and other insects might combat disease is through the shielding effects of their microbial symbionts. Bees carry a diverse assemblage of bacteria, very few of which appear to be pathogenic. Here we explore the inhibitory effects of these resident bacteria against the primary bacterial pathogen of honey bees, Paenibacillus larvae.
Results
Here we isolate, culture, and describe by 16S rRNA and protein-coding gene sequences 61 bacterial isolates from honey bee larvae, reflecting a total of 43 distinct bacterial taxa. We culture these bacteria alongside the primary larval pathogen of honey bees, Paenibacillus larvae, and show that many of these isolates severely inhibit the growth of this pathogen. Accordingly, symbiotic bacteria including those described here are plausible natural antagonists toward this widespread pathogen.
Conclusion
The results suggest a tradeoff in social insect colonies between the maintenance of potentially beneficial bacterial symbionts and deterrence at the individual and colony level of pathogenic species. They also provide a novel mechanism for recently described social components behind disease resistance in insect colonies, and point toward a potential control strategy for an important bee disease.
2006 Research Projects
Varroa mite control using mineral oil and essential oils in honey bee colonies
Jeff Pettis
USDA-ARS Bee Research Laboratory
Researcher’s Summary
To examine the effects of mineral oil and essential oils our laboratory conducted field experiments; three in Florida and one in Beltsville, Maryland. The Florida studies involved testing two application methods for mineral oil and essential oils; the Maryland study involved only mineral oil. The Florida studies determined that the essential oil formulations did not affect brood or honey production but our data on Varroa control were inconclusive. Direct application of mineral oil or in combination with essential oils did not inhibit the re-use of these combs for brood rearing. The Maryland study focused on the direct application of mineral oil to the top bars of hives over four weeks and demonstrated that mineral oil alone could reduce Varroa populations by 33% but were not different from the water treated controls. Thus the addition of any liquid, oil or water, reduced mite population equally; again with no adverse effects on brood production or queens. We did not achieve our goal of a viable mite control recommendation with any of our treatment regimes, low mite populations made it impossible to draw definitive conclusions. We can say that the treatments did not adversely affect brood or honey production and no queen loss was noted.
2006 Research Projects
Co-encapsulation of attractants to Improve Biocontrol of Varroa in Honey Bee Hives
Kelly Cartwright
Agricultural Research Initiatives, Inc.
Researcher’s Summary
Experiments were conducted both in the field and in the laboratory to assess the potential of using a proprietary microencapsulation system to improve biological control of Varroa mite(s) by Metarhizium anisopliae. In preliminary field tests, with a limited number of hives (a total of 3 hives per treatment) and a lack of spacing opportunity between treatment groups, no significant differences were detected between control treatments and those treatments containing the microcapsule system even though the mite infestation levels were adequate. In these same tests, Apiguard or M. anisopliae alone reduced mite levels initially but, as alluded to, no significant differences were noted at the end of the 45 day experimental period. The formulated material handled well and applied in a similar way to commercial applications.
Two laboratory experiments were performed for preliminary assessments of the microcapsule system to influence direction patterns of mites based on attractants present. There was a large degree of variability between experiments. In one experiment, the vast majority of mites moved towards the attractants and subsequent M. anisopliae. As a result, the majority of mites died in this test. In a second test, however, this was not as consistent nor obvious. Overall, the microcapsules did not seem to influence mite patterns though some degree of mite behavior may be affected simply by the attractants themselves.
Overall, suitable attractants and/or masking compounds remain a worthwhile research effort. These experiments were preliminary and exploratory in nature into a microcapsule system that has not been evaluated prior to this effort. Hopefully, some of the work contained in this project has laid additional groundwork to research already conducted (or being conducted) work in this area. The significance of the Varroa problem will continue to justify research into unusual areas of work in attempts to better control this ectoparasitic mite.
2006 Research Projects
Investigating Bacillus thuringienses CRYIII toxin for the biological control of Small Hive Beetle
Audrey Berry
Mississippi State University
Investigating Bacillus thuringienses CRYIII toxin for the biological control of Small Hive Beetle (Aethina tumida)
Abstract from final report
Laboratory assays were conducted on small hive beetles (Aethina tumida Murray) to determine the toxicity of a Bacillus thuringiensis ssp. tenebrionis (Btt) formulated insecticide and the Cry3Bb1 insecticidal protein to larvae. Small hive beetle larvae were fed four labeled rates of Novodor® FC and two rates of the purified protein then observed for mortality in the larval, pupal, and adult life stages. All treatment groups were run simultaneously with a positive control. Dead larvae from Novodor® treatment groups corresponding to 2 and 4 quarts per acre were examined for Btt infection by making smears and slides of the corpses. While Btt was viable in all deceased larvae, it was not abundant enough to be considered the cause of death. Furthermore, other microorganisms were recovered from both treatment and control groups that may have contributed to mortality in both groups. There was no significant difference in larval or adult weights or emergence in control and treatment groups, and mortality in Novodor® treatment groups did not exceed 20%. Cry3Bb1 groups were fed 50 or 100 ppm purified protein and run simultaneously with a negative control. Mortality in the 100 ppm group reached 27%, while the control and 50 ppm groups both experienced a 7% loss. Larval weights did not differ significantly and adult weights could not be estimated. Results from this study show the Cry3Aa and Cry3Bb1 Btt toxins to be non-lethal to small hive beetles.
2006 Research Projects
Is Propolis Effective Against American Foulbrood and Varroa Destructor?
Marla Spivak
University of Minnesota
Findings showed that Propolis was not toxic to bees, but not effective against AFB. Propolis did show promise in treating for Varroa mites. NHB provided funding for a follow-up study in 2007.
2006 Research Projects
Honey Industry
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