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

Alternative treatments for Nosema disease in honey bees will be evaluated using experimentally infected honey bees isolated in cages. Pathology and biotic potential of two species of Nosema infecting honey bees will be evaluated at various temperatures and under different microbiocide treatment regimens. Two methods of measuring pathology will be evaluated. Counting spores with a hemocytometer is the commonly employed and far easier method of determining disease intensity and making decisions for treatment. However, vegetative forms of Nosema cannot be counted in this way and actual pathology is caused by damage to epithelial gut cells. There is evidence that the ratio between spore production and parasitism is different between the 2 species of Nosema that infect honey bees. Evaluating the relationship between numbers of parasitized epithelial cells in the gut and numbers of mature spores for each species of Nosema will help determine how well counting spores reflects actual pathology and will eventually improve the action threshold for this disease. There is only one proven treatment for Nosema currently and it is known to suppress the pathogen, not necessarily cure a colony. Overuse of a single compound will likely produce resistance, leaving no treatments for Nosema. Several compounds show promise for treatment of Nosema but more research is needed. There are no data regarding actual intensity of cell parasitism under these treatments and no data about the mode of action or the way these putative treatments affect the life cycle of the pathogen. Clarification of these problems will help determine the best alternative treatment, and improve understanding of the disease.

1. Determine the efficacy of three compounds (Honey-b-healthy, Nosevit and Thymol) previously shown to have potential efficacy in preliminary trials against Nosema, at 25C, 33C and 37C through experimental infection and treatment of caged honey bees. These temperatures were chosen to include upper and lower limits for Nosema. Quantify the success of treatments though both spore counts and microscopic analysis of the epithelial cell damage in the honey bee gut.

2. Determine the relationship of disease intensity (% parasitized gut epithelial cells) to spore production in both species of Nosema during treatment. This approach should help understand why there are great differences in spore counts between Nosema species.