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Research Project: Longitudinal Studies to Determine the Causes of Honey Bee Loss

Location: Invasive Species and Pollinator Health

2021 Annual Report

Pollinators, such as honey bees and other insects, are critical components of both natural ecosystems and agroecosystems, ensuring the production of many agronomic crops. Objective 1: Employing long-term, longitudinal studies of honey bee survivorship under current management conditions for honey bees used as pollinators and honey producers, elucidate honey bee forage needs and causes of mortality to serve as the basis for best management practices for pollination of specialty crops such as almond. [NP305, Component 2, Problem Statements 2A, 2B, 2C]

Honey bees are the main pollinators of crops in the United States and worldwide. Losses of honey bees due to a variety of factors are unsustainable at the current levels of over 30 percent. To mitigate these losses, it is necessary to determine their causal factors; however, long-term baseline data for colony survivorship is not available that can be used to parse the relative importance of suspected factors. It is therefore crucial to develop such a methodology, particularly as part of long-term longitudinal studies of spatial and temporal changes in bee populations exposed to a number of abiotic and biotic stresses and management practices. These longitudinal studies may incorporate research on pesticide, pathogen/pest, and nutrition/forage or other bee health effects, using hives that are stationary as well as those that follow pollination service migratory routes. The proposed longitudinal studies support ARS National Program on Production (NP305) Action Plan research objectives; Component 2: Bee Health; Problem Statements 2A: Bee Management—Improving Bee Nutrition and Performance, 2B: Bee Health—Mitigating the Impacts of Pathogens, Pests, and Pesticides, and 2C: Maximizing Bee Pollination and Quantifying Bee Forage Requirements of the Action Plan.

Progress Report
This is the final report for bridging project 2030-21000-053-00D, which replaced expired project 2030-21000-001-00D, “Longitudinal Studies to Determine the Causes of Honey Bee Loss.” This bridging project has been replaced by new project 2030-21000-055-00D, “Conduct Longitudinal Studies on Colony Performance and Explore Near-term Effects of Nutritional and Agrochemical Stressors on Honey Bee Health.” For additional information, see the new project’s report. In support of Objective 1, cooperator apiaries have been identified and experimental colonies have been set up in each apiary. Colony monitoring is being standardized. We are generating datasheets and training a technician who will assist in the monitoring process. Monitoring of colonies will continue through the year. Automated temperature monitoring sensors deployed in each of the experimental hives will record hive temperature data periodically and upload recorded data to computers. An experiment was completed assessing the effects of insect growth regulators (IGRs) on queen egg production, changes in worker physiology and egg hatching rates. Samples and data collected from this experiment were analyzed, and a manuscript was published. An experiment assessing the effects of sublethal developmental exposure to insect growth disruptors (IGDs) on worker behavior was performed and a manuscript is in preparation. In addition, in support of Agreement # 2030-21000-053-02S, experiments designed to determine the impact of nutrition, specifically dietary phytochemicals on the expression of hypopharyngeal glands (HPGs) in newly emerged worker bees, were completed. Data collected were analyzed to show that supplementation with p-coumaric acid improved HPG expression. A manuscript is under preparation.

1. The establishment of the Long Term Honey Bee Research (LTHBR) system in California. Beekeepers experience high overwintering honey bee colony losses, while the demand for colonies to meet pollination services in almond orchards continues to grow exponentially. ARS researchers in Davis, California, have established a Long Term Honey Bee Research (LTHBR) system to provide insights for improving colony survivorship. Establishing the LTHBR system in California allows for researchers to record long-term data on colony performance and related biotic and abiotic factors that determine hive health. Experimental colonies have been set up in stakeholder apiaries and automated temperature monitoring sensors are in place within colonies to periodically collect and store abiotic parameters. Data from the LTHBR will shed light on the influence of climate change (e.g., drought and temperature) on honey bee health and pollination services, as well as enable the development of relevant management strategies.

2. Insect growth regulators may affect honey bee embryos following maternal exposure. Honey bee pollinators may be exposed to insect growth disrupting pesticides while foraging, which can be lethal to immature bees. ARS researchers in Davis, California, have demonstrated that insect growth regulators may affect honey bee embryos following maternal exposure. Using a specialized cage design to quantitatively assess honey bee queen egg production rates under exposure to insect growth disruptors (IGDs), ARS researchers demonstrated that IGD pesticides can affect egg hatching rates without affecting queen egg laying rates or queen survival. These results provide evidence that sublethal effects of a commonly used insecticide can have long-term consequences on honey bee colony performance. Understanding these sublethal effects will enable the development of management recommendations for improved risk mitigation strategies to protect pollinators, while increasing crop yields.

Review Publications
Fine, J.D., Corby-Harris, V.L. 2021. Beyond brood: the potential impacts of insect growth disruptors on the long-term health and performance of honey bee colonies. Apidologie. 52:580-595.
O'Brien, C., Seshadri, A.H. 2020. If you build it, they will come – agroecosystem based management practices to support pollinators. Annals of the Entomological Society of America. 114(3):322-328.