Last week we reviewed some key aspects of fall varroa mite management, with emphasis on making sure we are using treatment products responsibly and when our sampling indicates that treatment is warranted. Continuing on the topic of fall pest and disease management, this week we will explore some recent studies investigating seasonal trends of Nosema with consideration of the shift in Nosema species prevalence. Fall presents an opportune time to perform Nosema sampling and to treat if this indicates the infection level is above the economic threshold.
Nosema in Atlantic Canada
In the world of beekeeping and honey bee research, the topic
of Nosema has gained increasing attention thanks to the realized shift in
prevalence of Nosema species, from Nosema apis towards Nosema ceranae.
Last year, ATTTA shared interesting, significant results from our regionally relevant
investigation: Evaluating
Efficacy of Fumagilin-B® Against Nosemosis and Tracking Seasonal Trends of
Nosema spp. in Nova Scotia Honey Bee Colonies (McCallum et al. 2020).
The results
of this study (as outlined in Blog #25) revealed a shift in Nosema species
infecting honey bee colonies in Atlantic Canada. It also identified seasonal trends in
infection levels and treatment efficacy (McCallum et al. 2020) specific
to our region. This research helps build a better comprehension of nosemosis but
emphasized a knowledge gap in understanding best management practices for
control of Nosema, especially Nosema ceranae.
Lately, new
research has added to our understanding of Nosema. Two examples of this type of work are
explored below.
Seasonality of Nosema ceranae Infections and Their Relationship with Honey Bee
Populations, Food Stores, and Survivorship in a North American Region (Emsen et
al. 2020)
To help address the lack of knowledge and understanding of Nosema
ceranae, a recent study from Southern Ontario aimed to determine how an
infection impacts honey bees in a realistic beekeeping setting, and optimal
treatment strategies to control an infection. Contributing to this aim,
researchers investigated seasonal changes in the intensity, prevalence, and
spore viability of Nosema ceranae infections, and explored how an
infection impacts colony conditions and honey bee longevity.
This study revealed interesting, significant results that
contribute to our knowledge and understanding surrounding Nosema ceranae and
are summarized below:
- Intensity: higher in spring/summer than fall
- Prevalence: higher in spring/summer than fall
- Spore viability: ~4x higher in spring than summer/fall
- Colony conditions: low level N. ceranae infection (<1,000,000 spores/bee): more bees, brood, pollen stores, and honey stores than high level infection (>2,000,000 spores/bee)
- Longevity: decreased survivorship rates in infected worker bees
This study also emphasizes the need for additional
investigations on the epidemiology and the impact of Nosema ceranae in
honey bee colonies in other geographic regions, due to potential regional
differences in disease virulence, susceptibility, and therefore overall impact.
Mitigating Nosema ceranae infection in western honey bee (Apis mellifera) workers using propolis collected from honey bee and stingless bee (Tetrigona apicalis) hives (Naree et al. 2021)
Fumagillin has been, and continues to be, the best treatment
option for controlling Nosema infections. However, reliance on a single
treatment product combined with concerns regarding human exposure to
fumagillin, and the shift in prevalence from N. apis to N. ceranae
encourages research for finding novel treatments for Nosema.
In this recent study, the efficacy of two kinds of propolis
(from honey bee and stingless bee hives) as a treatment for Nosema ceranae
infections was investigated. Results revealed in this investigation are
interesting and significant. The main
points are outlined below:
- Increased probability of infected bee survival with either kind of propolis treatment
- Decreased infection rate and infectivity in bees treated with either kind of propolis
- Increased protein contents in both hypopharyngeal glands and hemolymph in bees treated with either kind of propolis
Although these are interesting and exciting results, more
research is needed to improve understanding of how propolis works to combat Nosema
ceranae infections, and how treatment efficacy varies depending on
geographic location.
Emsen, B., Mora, A., Lacey, B., Eccles, L., Kelly, P. G.,
Medina-Flores, C. A., Petukhova, T., Morfin, N., & Guzman-Novoa, E.
(2020). Seasonality of Nosema ceranae Infections and Their Relationship
with Honey Bee Populations, Food Stores, and Survivorship in a North American
Region, Journal of Veterinary Sciences, full text available online.
McCallum,
R., Olmstead, S., Shaw, J., & Glasgow, K. (2020). Evaluating Efficacy of
Fumagilin-B® Against Nosemosis and Tracking Seasonal Trends of Nosema spp. in
Nova Scotia Honey Bee Colonies, Journal of Apicultural Science, full text available online.
Naree, S., Benbow, M. E., Suwannapong, G., & Ellis, J.
(2021). Mitigating Nosema
ceranae infection in western honey bee (Apis mellifera) workers
using propolis collected from honey bee and stingless bee (Tetrigona
apicalis) hives, Journal of Invertebrate Pathology, full text available online.
Connecting with ATTTA Specialists