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Photo A. Hygienic bees detect,
uncap and remove a sealed, 5th instar larva that is infected
with either American foulbrood or chalkbrood disease. Hygienic
bees are able to detect that the larva is diseased before it
reaches the infectious stage; in this way, hygienic bees eliminate
the pathogen and avoid further disease transmission through
the colony. |
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Breeding for Resistance
We have been breeding honey bees for resistance to diseases and
Varroa destructor since 1994. The most devastating disease of honey
bees is American foulbrood (AFB), a highly infectious bacterial
disease of brood (larvae). We have demonstrated that honey bees
bred for hygienic behavior, a genetic trait, demonstrate good resistance
to AFB and also to a fungal disease, chalkbrood [1].
Bees bred for hygienic behavior are able to detect and physically
remove disease-infected brood from the colony before it becomes
infectious. Hygienic bees are able to detect and remove diseased
brood before the human eye can detect any sign of disease symptoms.
When bees remove the disease in the non-infectious stage, it prevents
the disease from spreading throughout the colony.
Our research has shown that bees bred for hygienic behavior also
display resistance to V. destructor mites because they are able
to detect and remove broods infested with the mites [2].
This mite parasite alternates between feeding on blood of adult
bees, and feeding and reproducing on the pupal stage of bees. Bees
that remove mite-infested pupae from the nest interrupt the reproductive
cycle of the mite by eliminating the offspring of the mite developing
within a wax-sealed cell (Photo A).
We have bred hygienic behavior into an Italian line of honey bees.
However, the behavior is present in all races and lines of honey
bees in the US (and the world!), and can be easily selected for,
using the methods described below. Our "MN Hygienic Line"
of bees is available commercially in the US and has become widely
accepted by beekeepers. However, our hope is that beekeepers select
for hygienic behavior from among their favorite line of honey bee,
whether it be Carniolan, Italian, Caucasian or other species. In
this way, there will be a number of resistant lines available within
the U.S. to maintain genetic diversity -- the perfect way to promote
the vitality of our pollinators.
Much of our research effort is in evaluating our MN Hygienic Line
against other lines of commercially available honey bees to ensure
that it is resistant to diseases and can actively defend itself
against the mite pests, resulting in lower mite levels. We also
evaluate the honey production, gentleness and wintering ability
of our line to ensure that it is acceptable to both commercial and
hobby beekeepers [3, 4].
In the last several years, we have made great strides in increasing
the degree of resistance of our line to the mites, so that the frequency
of treatments to control the mites can be greatly reduced and alternative
treatments (such as organic acids and botanical oils) can be used
to reduce mite loads.
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