New research indicates that bumble bees have higher levels of disease pathogens when their habitats have low-quality landscape, fewer flowers, a lack of spring flowers, low quality nesting opportunities, and when they live in areas with a high number of commercial or managed honeybee hives.

The study is one of the first to use data from a broad geographic scale in evaluating the relative role of landscape features on the distribution and loads of key pathogens and parasites in wild bees.

According to the researchers, the study examined how various environmental and landscape characteristics influence infectious disease prevalence and bee health, and the results can be used by those who manage and support the conservation of bee species that provide pollination services in agricultural and natural ecosystems.

In this unrelated 2:20-minute video by Inspiring Ideas we see what they refer to as tired bumble bees falling asleep in flowers... are they sleeping? We'll leave that to you to decide but these are some great images of bumblebees and flowers.



Lead author Darin J McNeil, post-doctoral fellow in the Insect Biodiversity Center in Penn State’s College of Agricultural Sciences, explains that the decline in managed and wild bee populations around the world recently can be attributed to extensive degradation of and loss of habitat and a lack of nest sites and flowers. This then contributes to loss of diversity and abundance of wild bees.

Further, he reminds us that bee health is known to be undermined by pesticide exposure and poor nutrition. This increases susceptibility to disease since bee immunity is weakened, which opens the door to rising levels of novel bee pathogens in honeybees and bumblebees.  

Bees are likelier to be nutritionally challenged and nutrient deprived in landscapes with fewer flowering plants. Poor nutrition deprives the immune response and increases the parasite and pathogen loads.

Co-author Heather M. Hines is an associate profession of biology and entomology. She explains that there are many interacting factors in disease virulence and prevalence, and it can be challenging to predict in wild bee populations. The composition of a bee community is likely to be a big influence on the loads and incidence of a particular parasite or pathogen in that bee population. There are often higher loads of pathogens, viruses and parasites, in wild bumblebees that live in the presence of honeybee colonies, where there are more pathogens that are transmitted to native bees.

This study focused on the researchers screening for the three pathogens known to infect bees: black queen cell virus, deformed wing virus and Vairimorpha, a microsporidian parasite, and for expression of a gene that regulates immunity.

To measure pathogen loads, the research team collected and analyzed bumble bee workers from the common eastern bumble bee, or Bombus impatiens, the most abundant bumble bee species across Pennsylvania in a variety of habitats at peak bumblebee time (late June to mid-July) in 2018 and 2019. Geographic location played a role.

Using statistical analysis techniques, their findings indicate that the highest pathogen loads were in bumble bees with the lowest quality landscapes, the main drivers being spring florals and nesting habitat, while exposure to honeybee apiaries increased pathogens, and a positive relationship was found between rainfall and Vairimorpha loads. 

The results of this study highlight the need to create high-quality landscapes and maintain good ones that have abundant floral and nesting resources, according to McNeil. This will support healthy wild bee populations.  

The findings also focus on the value of investing in spring floral resources because this is often overlooked in favor of garden plantings for pollinators that are aimed more at mid-summer forage.

Researchers hope to incorporate these findings into Beescape – an online tool for people across the USA to evaluate the quality of their landscape. They recommend that everyone reads up on best practices to create forage and habitat for bees in their geographical area, for urban, agricultural and natural landscapes.

There is much more to this study, so if you would like to read this research in more depth, the findings can be found in Scientific Reports.