Rusty-Patched Bumble Bee: A Beloved Bumble Bee That Needs Our Help!
The rusty patched-bumble bee (RPBB), Bombus affinis (Fig 1), is one of the 21 bumble bee species in the Eastern/Midwestern region out of 48 bumble bee species documented in the United States. RPBB used to be widespread throughout the region but has declined recently to small pockets in a few states, including Wisconsin (Fig 2). RPBB holds a special place for us here as Wisconsin represents one of the bigger areas where they are found as well as where suitable habitat for this species is present (Fig 3).

RRBB is not the only species of bumble bees (e.g., Cameron et al. 2011), bees overall (e.g., Potts et al. 2010), and insects in general (e.g., Hallman et al. 2017), that have been reported in sharp declines over the last decades. This overall trend in bee declines has, at least in some way, contributed to RPBB becoming the poster child for bee conservation efforts. In 2017, RPBB became the first bee species to be placed on the Endangered Species Act by the U.S. Fish and Wildlife Service as it was reported to have declined by almost 90% since the late 1990s in addition to its rapidly shrinking range. RPBB’s drastic decline has been attributed to a combination of factors, including pathogens, exposure to pesticides, habitat loss and degradation, competition and disease introduction from commercial bees, and climate change.

RPBB, like other bumble bee species, lives in colonies formed by solitary queens that emerge from overwintering sites in early spring. At this time of year (April/May), the bumble bees are bigger than later in the spring and summer as they are the overwintering queens. Bumble bee queens are some of the first bees we see flying around in the spring. The queens require nectar and pollen-producing flowers for food and undisturbed nesting habitat near food sources to survive and start a new nest. Once the queen has provisioned the nest and laid the first brood, the bees that then emerge will take over the foraging for food and taking care of the nest for the rest of the summer. These new bees are worker bumble bees and are smaller than the queen. All the workers and the founding queen will die at the end of the summer and the new queens produced at the end of the summer will mate and find a hiding place to overwinter in.

RPBB (as well as other pollinators) requires high quality foraging resources, nesting sites, overwintering sites, and protection from pesticides, introduced diseases, and landscape disturbances. What can we do? It is important to be good stewards of our land and provide floral resources, minimize soil disturbances to protect nesting sites, and to protect pollinators from harmful pesticides. Tables 1 and 2 taken from the publication Protecting pollinators and improving pollination on Wisconsin cranberry marshes show the relative toxicity of insecticides and fungicides, respectively, to bees. Please note that these tables were put together in 2018 and some products may no longer be registered or allowed by handlers.
It is also very important to think about the residual activity of some of our pesticides when bringing managed bees on the marsh. Some pesticides, such as Lorsban, have fairly long residual activities, and we should think about holding off broad spectrum insecticide applications at the very least 3 days before managed bees arrive on the marsh (Cutler et al 2014). In addition, it is important to remember that native bees, such as RPBB, are present on the marsh throughout the year and spraying less toxic pesticides and in the evening, can help reduce exposure. For more info on how to protect and promote pollinators, refer to the publication Protecting pollinators and improving pollination on Wisconsin cranberry marshes.
Happy growing season!
References:
Cameron SA, Lozier JD, Strange JP, Koch JB, Cordes N, Solter LF, Griswold TL. Patterns of widespread decline in North American bumble bees. Proceedings of the National Academy of Sciences. 2011, 108 (2) 662-667.
Cutler GC, Purdy J, Giesy JP, Solomon KR. Risk to pollinators from the use of chlorpyrifos in the United States. Rev Environ Contam Toxicol. 2014, 231:219‐265.
Hallmann CA, Sorg M, Jongejans E, Siepel H, Hofland N, Schwan H, et al. 2017. More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLoS ONE 12 (10): e0185809
Potts SG, Biesmeijer JC, Kremen C, Neumann P, Schweiger O, Kunin WE. 2010 Global pollinator declines: trends, impacts and drivers. Trends in Ecology and Evolution, 25: 345-353.
This article was posted in Insects and tagged bumble bee, CCMJ, insects, rusty-patched bumble bee, WFN.