Effects of natural compounds on Nosema diseased honeybees in laboratory conditions.

Nosemosis is one of the most widespread honeybee diseases, caused by the microsporidian Nosema apis. The only effective substance against this parasite, fumagillin, is no longer available for use in most European countries. For this reason, the potential of some natural compounds for the control of Nosema infection in honeybees was investigated. Newly emerged adult bees were artificially inoculated with a known amount of N. apis spores by force-feeding the bees with a sucrose suspension. Groups of 30 bees were kept in small cages for 25 days and were fed with candy treated with thymol, resveratrol, vetiver oil, lysozyme or with untreated candy. Two randomly chosen individuals were collected from each cage at different times and examined to measure the progress of the infection; the number of dead and living bees was recorded every 3 days. From the results it emerged that thymol and resveratrol were the most promising in effectively reducing Nosema infection.