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United States Department of Agriculture

Agricultural Research Service

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2011 Annual Report

1a. Objectives (from AD-416)
1) Develop improved understanding of factors weakening hive vigor and foraging efficiency, and provide economically sound integrated pest management (IPM) approaches to lessen the effects of these factors. Improve IPM tactics for control of key pests of honey bees, including Varroa mites, and the small hive beetle. Develop IPM strategies to lessen pesticide/antibiotic use in managed honey bee colonies, biorational compounds, and sustainable agricultural practices/IPM tactics for use in crop production that will lessen bee exposure to pesticides. 1A) Develop IPM tools and methodologies for control of key pests, and miticide resistance management programs to preserve useful chemical options. 1B) Determine the impact of the small hive beetle on colony development and longevity, and develop management systems for controlling the beetle in hives, including use of antifeedants for protection of protein supplements from small hive beetle damage. Develop effective control programs for management of small hive beetle in bee hives, with the goal to prevent contamination of bee products. 1C) Determine impacts of pesticides on foragers, both acute lethal effects and sub-lethal effects on bee behavior due to chronic exposure, and develop methods to mitigate bee losses due to pesticides, including management strategies for minimizing exposure of bees to pesticides in the field. 2) Use molecular approaches to investigate the physiological basis for bee immune responses to fungal pathogens such as chalkbrood, and develop strategies for controlling natural honey bee diseases. Identify molecular bases for honey bee physiological responses to chalkbrood. Identify and assess the role of genes that could potentially be involved in the anti-fungal activity.

1b. Approach (from AD-416)
Objective will be achieved through development of a combination of different IPM tactics (e.g., soft pesticides, acaricide rotation program, traps, lures) for control of pests, parasites, and diseases of the honey bee, and protection of hive products. It will also involve molecular studies to better understand the genetic basis of insect resistance to the fungal pathogen Ascosphaera apis, the causative agent of chalkbrood disease in honey bees. We will conduct a genome–wide screening of the honey bee immune cDNAs and will monitor the expression profile of larval genes by direct comparison of immune vs. pre-immune cDNAs. We will then utilize qRT-PCR approach to monitor expression profiles of the selected genes, identified through the genomic screens of bee's cDNAs, to better understand the correlation between changes in the level of gene transcripts and the progression of the disease.

3. Progress Report
Progress on this new project focused on two major problems: 1) the need for improved management of honey bee colonies; and 2) improved health of managed bees. Diseases, parasites, and other stress factors working synergistically weaken honey bee health and may play a major role in the loss of bee populations in recent years. Among a large number of bee diseases, nosemosis and chalkbrood have been on the rise. Using a microarray approach, we examined the impacts of Nosema infection on the expression of the honey bee gene expression profile, showing significant changes in the expression profile of genes affecting metabolic and nutritional status. To improve control of Nosema ceranae in bee colonies, scientists at Weslaco, TX, tested a new active ingredient showing a reduction of spore counts in affected bee colonies. We also investigated mechanisms employed by this same fungal pathogen. Data analysis captured a significant number of differentially expressed genes related to fungal reproduction and host invasion. Data produced in this study presents a unique opportunity to improve our understanding of the highly complex nature of host-pathogen interactions and to ultimately develop new approaches to disease control. A number of studies were conducted to develop control for honey bee pests, including Varroa mites and Small Hive Beetles (SHB). To develop control of the SHB in honey bee colonies, we conducted studies on the aspects of SHB biology and ecology, including determining food consumption rates, the effects of competition on larval growth and subsequent development, and the depth of soil required for pupation. To develop control for Varroa destructor, the most devastating parasite of honey bees, we are conducting a large field experiment using a newly developed active ingredient. This phase of the project involves validating the data generated in our previous experiments and developing a reliable delivery mechanism. A new delivery device must be inexpensive to manufacture, must reliably provide an acceptable daily dose during two honey bee brood cycles, and will self-degrade at the end of a treatment. To fine-tune this delivery method, we have already tested this device in small-scale trials (25-30 colonies). In additional experiments, we have tested two different formulations and delivery methods of amitraz against Varroa mites. 1) An amitraz strip product (Apivar); and 2) as the registered product Mitaban. Tests using Mitaban demonstrated that it is efficacious for varroa mite control in honey bee colonies.

4. Accomplishments
1. Honey bee responses to fungal diseases. Using a genome-wide approach, ARS researchers at Weslaco, Texas, identified a large set of genes in the honey bee fungal pathogen Ascosphaera apis. Data analysis revealed key components responsible for pathogen reproduction and host invasion. A wide variety of molecules found in this study are well-known target sites of the anti-fungal drugs currently used in treatments of animal diseases, and thus can be tested against A. apis, the chalkbrood fungus. Results of this study in combination with our previous data support the theory that activation of disease defenses in the honey bee negatively affects most of the bees' biological functions, including the nutritional status and response to pesticide poisoning. This research will lead to development of new management strategies in support of healthy bee colonies.

2. Detection of diseases in beehives. Scientists at Weslaco, Texas, developed a new diagnostic tool for the detection of Nosema infection in honey bee samples. This new highly specific sensitive test, based on an antigen capture assay that detects Nosema spore wall protein, is capable of detecting Nosema-infected bees. Following the development of a reliable field diagnostic tool, scientists are now using the same antibody-based approach to develop a high-throughput laboratory test (ELISA) for the detection of Nosema in bee hives. Furthermore, in response to the increased incidence of fungal diseases in bee colonies, Weslaco scientists developed a simple DNA-based method for detecting chalkbrood, A. apis fungus, disease in bee brood. This test will allow detection of the fungus prior to clinical signs of the disease. Chalkbrood disease has recently become more prevalent in managed hives. Research indicates that high level of stress in the intense management environment may affect bees’ immune responses, making them more vulnerable to diseases.

3. Genes associated with Nosema infection determined by microarrays. In 2010, researchers at Weslaco, Texas, verified the infection status of bees infected with Nosema using DNA and microarray approaches. Microarray analyses revealed that Nosema infection alters bee biological processes regulating nutrition and behavioral maturation as expected, but Nosema infection surprisingly does not appear to significantly alter immune gene expression in midgut and fat body tissues up to 7 days post-infection. We will continue to examine impacts of infection by characterizing gene expression in immune-related tissues up to 2 weeks post-infection in bees infected with Nosema. These studies identify host response to Nosema infection and may lead to downstream applications in commercial management, improving the strength of the honey bee colonies.

4. Supplemental protein feedings offset impact of Nosema ceranae infection. Previous work by researchers at Weslaco, Texas, demonstrated that the negative impact of Nosema infection can be offset to a large degree with pollen substitute feedings. From October 2010 to January 2011, we compared the performance of heavily infected colonies fed eight commercial or beekeeper-prepared diets. Colony strength and brood nest sizes differed significantly, and performance was similar to that observed during a 2010 experiment with colonies having only mild infections. Improving nutritional status of bees will help to improve colony strength and will ultimately reduce the amount of the antimicrobial drugs used to control bee diseases.

Review Publications
Aronstein, K.A., Saldivar, E., Webster, T.C. 2011. Evaluation of Nosema ceranae spore-specific polyclonal antibodies. Journal of Apicultural Research. 50(2):145-151.

Meikle, W.G., Patt, J.M. 2011. The effects of temperature, diet, and other factors on development, survivorship, and oviposition of Aethina tumida (Coleoptera: Nitidulidae). Journal of Economic Entomology. 104(3):753-763.

Kanga, L.H., Adamczyk Jr, J.J., Patt, J.M., Cascino, J. 2010. Development of a user-friendly delivery method for the fungus Metarhizium anisopliac to control the ectoparasitic mite Varroa destructor in honey bee, Apis mellifera, colonies. Experimental and Applied Acarology. 52:327-342.

Last Modified: 05/26/2017
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