Testing the efficacy of three new alternative treatments for Nosema disease of honey bees in Tennessee

View the project final report

• 2009 annual report

Commodities

• Animals: bees

Practices

• Animal Production: herbal medicines, parasite control
• Pest Management: botanical pesticides, chemical control
• Production Systems: organic agriculture

The purpose of this study was to evaluate the effect of fumagillin, thymol, Nozevit and Honey-B-Healthy on Honey bees infected with either Nosema ceranae or Nosema apis. Prospective treatments for Nosema disease were evaluated by examining both mortality and spore production in caged honey bees. Bees used in the study were shaken from frames of uncapped brood taken from hives visibly free of Nosema infection. These bees were chilled with ice water, placed in cages (180 bees/cage) and immediately infected with either N. apis or N. ceranae through gravity feeders at a rate of 40,000 spores/bee. Treatment began 3 days after inoculation. Dead bees were removed and counted every subsequent day. Twenty-three days after inoculation, 10-15 bees were removed, abdomens were crushed individually in water, and spores were counted using a hemocytometer.

Although treatment greatly affected mortality, no difference was noted with respect to the species of Nosema. Bees treated with thymol and Honey-B-Healthy were found to have rates of mortality similar to uninfected bees. Bees treated with Nozevit had rates of mortality similar to untreated bees. Fumagillin improved mortality, but not to levels of uninfected bees (Table 2).

Honey-B-Healthy had no effect on spore production, therefore the reduction in mortality displayed under treatment must be attributed to positive effects on the bee itself rather than to an antagonistic effect on the pathogen. Fumagillin was the only compound to significantly and consistently reduce spore production. The failure of fumagillin to reduce mortality congruently is unexplained. Thymol and Nozevit had some effect on spore production but it was unclear how significant this effect was.

Introduction

The purpose of this project is to determine the best way to treat the honeybee disease Nosema in Tennessee by comparing the relative efficacy of fumagilin, thymol, Nozevit and Honey-B-Healthy on two species of Nosema through experimental infection and treatment.

Nosema infection (nosemosis) has been a longstanding problem in beekeeping. Queens infected with Nosema may be more prone to superscedure. Infected individual bees have a shortened lifespan and collect less pollen. Overall, nosemosis can lead to reduced productivity and colony death. Light infections are often asymptomatic.

The diagnosis of nosemosis has become more complex recently with the emergence of a new species of Nosema. Nosema apis has been a recognized (microsproridian) parasite of honey bees for a century. Until recently all nosemosis in honey bees was attributed to this species. Nosema ceranae, isolated in 1996, was initially thought to be an exclusive parasite of the Asian honey bee (Apis cerana). Nosema ceranae has recently been found infecting Apis melifera worldwide and throughout the United States. The exact distribution of each species is unknown. There is evidence that Nosema cerenae has greater pathogenicity and is more likely to cause hive collapse than N. apis.

Currently, the most commonly used treatment for nosemosis is Fumigillin. There is evidence it controls both species of Nosema quite well. Though it is currently very effective, there are concerns exclusive use of Fumagillin will foster resistance in Nosema. Furthermore Fumigillin is a teratogen and its use has been banned in the EU, in Great Britain and elsewhere.

Nozevit is an oak bark extract produced in Croatia. It has been found to be as effective as fumigillin in controlling Nosema ceranae.

Honey-B-Healthy is made form lemongrass and spearmint oil. It's marketed as a feeding stimulant and is has not been tested for Nosema control.

Several experiments have been done examining the usefulness of thymol in the treatment of nosemosis but the results are conflicting. In some cases, with rigorous control, thymol was found to work better than fumigillin for treatment of both Nosema ceranae and N. apis. Yet in other cases it was found to have no effect.

• Determine effect of treatment with thymol solution, Nozevit, Honey-B-Healthy, on honey bees infected with either Nosema apis or N. ceranae.
- Does treatment have an effect on longeveity of caged honey bees?
- Does treatment have an effect on Nosema spore production in caged honey bees?
- How do the prospective treatments listed above compare to Fumagillin, the standard for adequate treatment of Nosema in honey bees?
Determine if infection with Nosema apis is more or less virulent than infection with Nosema ceranae in terms of accelerated honey bee mortality.