Nosema bombi(Microsporidia: Nosematidae) and Trypanosomatid Prevalence in Spring Bumble Bee Queens (Hymenoptera: Apidae:Bombus) in Kansas

Abstract

Several species of bumble bees are declining in the United States; these declining populations often show higher prevalence of Nosema bombi, a microsporidian pathogen. To date, surveys of bumble bee pathogens in the United States have only been conducted on workers and males, yet the health of a population is ultimately dependent on the success of colony-founding queens. We conducted a molecular-diagnostic survey of the prevalence of N. bombi and trypanosomatids, such as Crithidia bombi, in six species of spring queens (n 5 142) collected in 2011 and 2013 at three sites in central Kansas. Nosema bombi was found in 27% of Bombus pensylvanicus and 13% of B. auricomus but was not found in the other species sampled. Trypanosomatids were only found in B. pensylvanicus (9%) during the May 2013 sampling period. The high prevalence of N. bombi in B. pensylvanicus is consistent with other surveys for this pathogen in other castes, but the high prevalence of N. bombi in B. auricomus is a novel finding. Although the conservation status of B. auricomus has not been thoroughly assessed, two recently published surveys showed that B. auricomus were less common in portions of the species' range. Based on those findings and an oft-cited link between N. bombi prevalence and bumble bee species' decline (e.g., B. pensylvanicus) in other studies, our findings suggest B. auricomus populations in Kansas may warrant further scrutiny.

One‐size does not fit all: at‐risk bumble bee habitat management requires species‐specific local and landscape considerations

“…This is because agricultural practises have been implicated in pollinator declines including: use of agrochemicals, tilling, and pathogen spillover from managed bees (Whitehorn et al ., 2012; Rao & Skyrm, 2013; Goulson et al ., 2015; McArt et al ., 2017). Previous studies have reported that B. pensylvanicus populations contain higher parasite loads than other non‐declining bumble bee species (Cordes et al ., 2012; Tripodi et al ., 2014). Managed bees often have higher pathogen loads than wild bees (Murray et al ., 2013), and bumble bees near greenhouses have observed higher pathogen infection rates than bumble bees away from greenhouses (Colla et al ., 2006).…”

Variation in North American bumble bee nest success and colony sizes under captive rearing conditions

“…The fact that they are within the subgenus Pyrobombus , have high rates of nest success, large colony sizes, and, in the case of B. huntii , sizeable gyne production may make them amenable for commercial production. Pyrobombus are pollen storers and have been reported to have lower rates of Vairimorpha bombi infection in wild populations ( Sladen 1912 ; Velthuis and van Doorn 2006 , Cordes et al 2012 , Malfi and Roulston 2014 , Tripodi et al 2014 ). Certain species of Pyrobombus have also been reported to emerge and establish nests early in the season, suggesting that these species have a longer time to persist and produce larger colonies compared with later emerging species ( Hobbs 1967 ).…”