RESPONSE OF NEW-ZEALAND HONEY-BEE COLONIES TO NOSEMA-APIS

Seventeen colonies of honey bees from 13 different sources were dosed with Nosema apis spores in sugar syrup. Spore loads carried by foraging bees were recorded for 11 weeks thereafter. Eleven further colonies, fed plain sugar syrup, were sampled as controls. Mean spore loads in all N. apis-dosed colonies increased to between 8 million and 27 million spores per bee two weeks after dosing. Five weeks after dosing, spore loads had decreased to levels comparable to those found in the control colonies (about 4 million spores per bee or less). There were no significant differences in the responses of colonies from different sources. Colonies from different sources showed a similar uniformity with regard to the rate of spread of infection among caged bees and chymosin levels in the guts of workers. These results show little variation in response to N. apis infection, and indicate a lack of genetic variability among New Zealand bees in respect of susceptibility to N. apis infection.