Group feeding

In contrast to inoculating individual bees with Nosema spores as described above, inoculation can also occur by providing a group of caged bees with a spore suspension in one or more common feeding devices that may be fed on ad libitum.  This method allows for individuals to be inoculated relatively quickly, and without the logistical and time constraints associated with individual feeding. Although not well studied, the primary disadvantage of group feeding of Nosema spores is the greater variance of Nosema intensity among caged individuals because of unequal distribution of the inoculum among individuals over time (Furgala and Maunder, 1961). Preliminary studies suggest group feeding is as effective at infecting caged bees as individual inoculation (Tanner et al., 2012). Greater cage replicates per treatment group may be required if group feeding of inoculum is used. Group inoculation of a spore suspension containing 10,000 and 33,300 spores per bee is sufficient to infect caged individuals (Webster, 1994; Pettis et al., 2012). 

Further details on group feeding are provided in the BEEBOOK chapter on maintaining bees in cages (Williams et al., 2013). For Nosema, for example, to mass inoculate 100 honey bees with approximately 10,000 Nosema spores per bee:

  1. Provide 1,000,000 spores in 4 ml 50 % (w/v) sucrose solution to guarantee that the entire volume will be consumed within approximately 24 hours.
    This short time period will ensure a similar initial inoculation period for all individuals, and help prevent bacterial degradation of unconsumed spores from occurring.
  2. Top up the feeder with 50 % (w/v) sucrose solution when the inoculation solution is close to empty so that the caged honey bees do not go without food.

To ensure all spores are ingested, small volumes can be regularly added throughout the day until one is confident that most spores have been consumed.

When cultivating Nosema spores, live bees can be killed 10 to 14 days post-inoculation, approximately when a full N. apis infection is reached (Fries, 1988), using methods described by Human et al. (2013) in the BEEBOOK.