A Country Abuzz with Pollinators

Published February 6, 2024

Over the past several years, the population of important pollinators has declined in the United States and internationally. Pollinators play a key role in agriculture since the majority of native plants require pollination by bees or other pollinating animals.

While much of this public focus has been on honey bees, bumble bees—native to the U.S and crucial pollinators of a multitude of native wild plants and crops—are also dwindling. The loss of bumble bees can have important consequences given their role as effective pollinators of native plants and a variety of crops including strawberries, tomatoes, and sweet peppers. Given their role in providing pollination services, bumble bees are the most popular species to breed commercially for the pollination of greenhouse crops in the U.S. When bumble bees forage for pollen, they engage in a form of pollination referred to as “buzz pollination.” Buzz pollinators grip flowers and vibrate their bodies, shaking the pollen loose from the flower. This makes it easier for bumble bees to collect pollen for them to snack on and feed their developing young (brood), but it has the added benefit of fertilizing flowers. While bumble bees are effective pollinators of greenhouse crops and some other commercial crops (e.g., blueberries, cranberries), breeding bumble bees commercially comes with potential risks.

The pollen used for commercial bumble bee rearing is often collected from honey bee colonies maintained by beekeepers. Unfortunately, this pollen may introduce contaminants, including pathogens, into commercially reared bumble bee colonies. Since the bumble bees in these colonies have the potential to encounter wild bees when deployed for pollination, these contaminants may have detrimental effects on both commercial bumble bee colonies and wild bee populations.

EPA researcher David Lehmann contributed to the development of a white paper recommending the development and implementation of a clean stock certification program to mitigate disease risk in commercial bumble bee production, which will in turn help reduce disease stressors on wild pollinator populations. The clean stock certification program was developed by the North American Pollinator Protection Campaign with input from several groups, including researchers at EPA. The program outlines several ways the commercial bumble bee rearing industry can reduce the spread of pathogens that have the potential to contribute to the decline of some populations of bumble bees, such as adopting disease and pest control measures. The NAPPC white paper also provides a list of priority actions that can be taken by the commercial bumble bee rearing industry, including outlining standards for a clean stock program, addressing shipment recording and tracking, and mitigating impacts to at-risk species.

Suggested best management practices for rearing facilities include:

Screening stock for pathogens,
Quarantining new stock prior to introduction into the rearing facility,
Implementing production controls to promote sanitary rearing conditions,
Treating or removing infected stock from the facility,
And identifying causative agents of disease and tracing disease outbreaks.

By implementing these measures and practices, bumble bee rearing facilities can lessen the risk of pathogen spread between commercial colonies and wild populations. Furthermore, a clean stock program could also help ensure the health of commercial bumble bee breeding stock, reducing the need to collect additional breeding stock from the wild and in-turn reduce the depletion of wild populations.

In addition to promoting the health of bumble bee populations through the development of the clean stock paper, EPA researchers also directly investigated the effects of acetamiprid, a neonicotinoid insecticide, on bumble bee survival and reproduction under laboratory conditions. Researchers used a microcolony model, which is where bumble bee workers are separated and confined without a true queen bee, prompting them to establish a worker as a false queen who lays unfertilized eggs which develop into males (drones). These drones tend to brood and build nest structures, performing similar tasks as worker bees in regular colonies. This makes the microcolony model an effective one to use for studies. Using this model, scientists at EPA performed studies introducing acetamiprid into the microcolonies and concluded that the pesticide significantly affects microcolony growth, development, and reproduction. However, this only occurred when the microcolonies were exposed to concentrations of the pesticide substantially higher than expected environmental concentrations that would be achieved when following label rates.

Developing models that predict bee colony behavior and programs that aim to lessen threats in commercial populations are important steps in understanding the causes of bee population decline and ways to reduce them. These initiatives hold promise not only for the preservation of diverse bee species but also for the broader implications on ecosystem and public health, given the integral role pollinators play in ecosystem services and sustaining our food supplies. As we move forward, continued support and implementation of such measures are crucial to ensuring the well-being of these vital contributors to our ecosystems and agriculture.

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A Country Abuzz with Pollinators

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