Location:2012 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:
This is the final report for the project 6204-21000-010-00D which terminated on 9/30/12. To better facilitate the overall research efforts involving honey bees, the program is being realigned with work to be incorporated into other existing research programs in Beltsville, MD; Baton Rouge, LA; and Tucson, AZ. In the duration of this Project most objectives were fully met and very good progress has been made on objective 1C (Effects of pesticides on forages). A number of different stress factors, including diseases, parasites, and chemicals, work synergistically to weaken honey bee health and may have played a major role in the loss of bee populations in recent years. Acute exposure to a range of pesticides has been shown to be detrimental to adult honey bee health. However, there is no clear data on the effects of chronic exposure of bees to sub-lethal concentrations of in-hive pesticides. To address this problem, we investigated chronic effects of Coumaphos and Fluvalinate embedded in wax lining of larval rearing cells on honey bee development and physiology. Compared to controls (no pesticides in wax), exposure to sub-lethal doses of pesticides significantly suppressed larval weight and increased developmental time. Additionally, Weslaco scientists have found that basal metabolic rate is significantly increased when 'low', but not 'high', concentrations of both Coumaphos and Fluvalinate are topically applied to young adult bees. Findings support the hypothesis that exposure to sub-lethal concentrations of pesticides can have significant negative effects on larval development and adult physiology. We have also investigated effects of bee diseases nosemosis and chalkbrood on bee health. Using microarray analysis, we examined the impacts of Nosema infection on honey bee gene expression and showed significant changes in the expression profile of genes affecting metabolic and nutritional status of bees. Furthermore, using transcriptome analysis we uncovered complex mechanisms employed by the fungal bee pathogen Ascosphaera apis during invasion of bee larvae. 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 develop new approaches to disease control. To develop control for Varroa destructor, Weslaco scientists conducted field trials using Pfizer-developed active ingredient. Data generated in these trials will be submitted to the EPA.
1. Chronic effect of chemicals on honey bee health. Weslaco, Texas, scientists investigated the effects of sub-lethal concentrations of pesticides on honey bee health. Data showed that chronic exposure of bee larvae reared in vitro in wax-lined cells spiked with Coumaphos and Fluvalinate resulted in reduced weight and increased developmental time of larvae. Additionally, scientists have found that basal metabolic rate is significantly increased when 'low', but not 'high', concentrations of sub-lethal concentrations of these pesticides are topically applied to young adult bees. Findings support the hypothesis that exposure to sub-lethal concentrations of pesticides can have significant negative effects on larval development and adult physiology.
2. Diagnostic tools developed for high-throughput detection and monitoring of honey bee diseases. Weslaco, Texas, scientists developed a new diagnostic tool for detection of Nosema infection in honey bees. This highly specific and sensitive test is based on an antigen capture assay that is designed to detect Nosema spore wall protein. Researchers are pursuing leads to transfer this technology to private industry. Furthermore, in response to increased incidence of fungal diseases in bee colonies, Weslaco scientists developed a simple DNA-based method for detection of chalkbrood disease in bee brood. These new tests allow early detection of bee infections, and therefore provide opportunities for timely colony management to prevent full-blown infection and colony collapse.
3. Development of a biopesticide against Varroa mites. Weslaco, Texas, scientists determined that multiple dust applications of a biopesticide are more effective compared to a single application. Data on biweekly mite fall and density of phoretic mites for experiments with two and three biopesticide applications were compared with similar data from single applications to estimate the effective duration of an application in a bee hive and the cumulative impact of repeated applications on bee colony growth. The proportion of fungus-infected mites recovered from sticky boards remained elevated longer after 2 or 3 applications than after a single application, and hives treated with 3 applications had significantly lower Varroa mite fall on to sticky boards than control hives after treatment. These studies included pre- and post-application Varroa mite fall, proportion infected mites, phoretic mite density, and bee hive growth, and thus provided a detailed understanding of biopesticide impact needed for the continued development of biopesticides as a Varroa control option.
4. Biology of the small hive beetle. Weslaco, Texas, scientists determined growth, development, reproduction, consumption, and competition parameters for small hive beetles, an important new pest of honey bees. Work was aimed at evaluating the relationship of beetle growth, development, reproduction, and longevity with respect to temperature, diet and crowding. Knowledge of these factors is needed for estimating beetle population growth and designing a population model, which can be used to examine beetle ecology and interactions with bees, and to evaluate the efficacy of control strategies. These are the first published estimates of several important life history parameters for a significant invasive bee pest. Parameters include consumption rates by larvae to be used in population modeling, and minimum development temperatures for all life stages needed to generate maps of the potential pest distribution.Aronstein, K.A., Oppert, B.S., Lorenzen, M.D. 2011. RNAi in agriculturally-important arthropods. In: Grabowski, P., editor. RNA Processing. Rijeka, Croatia: InTech. p. 157-180.