A Guide to the Honey Bee’s Protozoan Nosema Disease and Treatment Recommendations for Pest Control

Abstract

Like other insects, the honey bee is subjected to many diseases and their early detection allows
for prompt remedial action, and help in preventing serious outbreak and economic losses. These
diseases differ in their severity, but all of them can be prevented or controlled by proper
management. This handout offers information about field symptoms and diagnoses of the most
common honeybee protozoan Nosema disease and treatment recommendations for pest control.
There are two forms of the microsporidian Nosema associated with clinical signs of disease in
honeybees, Nosema apis and Nosema ceranae. The diseases of bee are usually divided into two
classes, those that attack the developing stages (the brood), and others that attack adult bees. In
general, the brood diseases are more serious, and their symptoms are more definite and
distinctive than those of the adult diseases. It takes experience and close observation to
distinguish a diseased larva or pupa from a healthy one, or one dead from other causes. This
experience can be gained only by frequent examination of the combs of a colony. For field
diagnosis, Nosema incidence in honeybee colonies peaks in early fall and early spring in only
adult bees by parasitizing their midgut, impairs the digestive process and causes bee’s starvation.
Adult bees have difficulty with controlling their fecal discharge and in heavy infestation, hive
bodies are often smeared with fecal deposits. For Nosema confirmation, adult bees must be
examined microscopically wherein spores are large, oblong shaped and highly uniform. For
determining the level of infestation, a haemacytometer can be used to calculate the number of
spores per adult bee. Though the diseases differ in their severity, but all of them can be prevented
or controlled by proper management. Such management includes knowing and recognizing the
symptoms of diseases, inspecting colonies regularly, and applying control measures promptly
when disease is found. This is one of the reasons why the beginning beekeeper must open the
colonies regularly. There are no IPM approaches specifically targeted against Nosema disease
and its management, however on the maintenance of robust colonies, there should be periodic
application of the antibiotic Fumagilin® B. The medication is mixed in sugar syrup according to
manufacturer’s recommendations and fed to bees in spring and fall. As with any medication, it is
applied in the off-season when there is no chance that it will contaminate marketable honey.
Drugs and antibiotics are effective in preventing disease, but cannot substitute for good
management practices. They must be used at the proper time and dosage to avoid contamination
of honey, and any recommended product is to be used only in accordance with the directions on
the product’s label.