Performance of hygienic honey bee colonies in a commercial apiary
Performance of hygienic honey bee colonies in a commercial apiary
Spivak 0
ry S. Reuter 0
0 Department of Entomology, 219 Hodson Hall, University of Minnesota , St. Paul, MN 55108 , USA
- Colonies with naturally mated queens from a hygienic line of Italian honey bees (Apis mellifera ligustica) were compared to colonies from a commercial line of Italian bees not selected for hygienic behavior. The following characteristics were compared: rate of removal of freeze-killed brood; amount of chalkbrood; incidence of American foulbrood; honey production; and the number of mites, Varroa jacobsoni, on adult bees. The hygienic colonies removed significantly more freeze-killed brood than the commercial colonies, had significantly less chalkbrood, had no American foulbrood, and produced significantly more honey than the commercial colonies. Estimates of the number of Varroa mites on adult bees indicated that the hygienic colonies had fewer mites than the commercial colonies in three of four apiaries. In previous studies on the relation between hygienic behavior and resistance to diseases and mites, the test colonies contained instrumentally inseminated queens. This is the first study to evaluate hygienic stock in large field colonies with naturally mated queens. © Inra/DIB/AGIB/Elsevier, Paris Apis mellifera / hygienic behavior / Varroa / chalkbrood / American foulbrood
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1. INTRODUCTION
For over 50 years, honey bee hygienic
behavior has been recognized as an
important mode of resistance to American
foulbrood disease (AFB) [
12
]. Woodrow and
Holst [
24
] stated,"... resistance to
American foulbrood consists of the colony’s
ability to detect and remove diseased
brood before the causative organism,
Bacillus larvae White, reaches the
infectious spore stage". Over 14 years ago, it
was determined that hygienic behavior
also is a mechanism of resistance to
chalkbrood, caused by the fungus Ascosphaera
apis (Maassen ex Claussen) Olive and
Spiltoir [
5
]. Recently it has been
demonstrated that hygienic bees detect and remove
pupae infested with the parasitic mite,
Varroa jacobsoni Oudemans [
1, 2, 13, 18
].
The removal of infested pupae interrupts
the reproductive cycle of the mite [
4, 14
].
However, the extent to which the
behavior actually reduces the mite-load in
infested colonies remains to be
determined.
Hygienic behavior occurs in approxi
mately 10 % of most commercial honey
bee populations thus far surveyed in the
US (Spivak, unpublished observations).
Despite the potential advantages of
maintaining hygienic honey bee lines, few
queen producers select for hygienic
behavior.
Rothenbuhler [
16
] postulated that the
behavior is controlled by two
independently assorting, recessive genes: one for
uncapping the diseased brood (u) and one
for removing diseased brood from the nest
(r) (but see Moritz [
10
]). When colonies
were composed of mixtures of hygienic
and non-hygienic bees (progeny of
instrumentally inseminated queens from
inbred lines), Trump et al. [
23
] concluded
that "for removal of all dead brood from a
small colony, the proportion of the bees
that must be of the hygienic type is higher
than 13 % but less than 50 %". These early
experiments suggested that a small
percentage of bees, possibly within particular
patrilines, may actually perform the
behavior.
The genetics of the trait may be
controlled by raising queens from hygienic
colonies and instrumentally inseminating them
with semen from drones of other hygienic
colonies [
5
]. However, instrumentally
inseminated queens are used only as
breeder stock in the beekeeping industry;
commercial beekeepers use naturally mated
queens in their production colonies.
Genetic control may be obtained by saturating
the mating area with hygienic drone
mother colonies [
8
]. If lines of bees
selected for hygienic behavior are to be utilized
by the beekeeping industry, it is first
necessary to examine colonies with queens
reared from hygienic stock and mated
naturally with unselected drones. Do
colonies with naturally mated queens reared
from a hygienic line remove freeze-killed
brood more rapidly than commercial
colonies? Do they have lower incidences of
chalkbrood and AFB? Do they have fewer
Varroa mites? And importantly, do they
produce as much honey? The present study
is the first to address these questions in a
commercial apiary.
2. MATERIALS AND METHODS
2.1. Hygienic breeding stock
The hygienic queens used in the experiment
were bred from ’Starline’ stock, derived from
Italian Apis mellifera ligustica Spinola, and
were maintained at the University of
Minnesota. The degree of hygienic behavior was
determined by a freeze-killed brood assay in
which the time was recorded for colonies to
detect, uncap and remove brood from a 5 cm x
6 cm comb section (containing approximately
100 capped larvae and pupae per side of the
comb) that had been cut from a frame within
the brood nest of the same or different colony,
frozen at -20 °C for 24 h, an (...truncated)