Effect of sugar syrup on larval survival in honey bee colonies affected by River disease

Abstract

The massive larvae death of the honey bees Apis mellifera, that occurs when the bees collect the secretions of the flatidae Epormenis cestri, is known as River disease in Uruguay. The beekeepers that find their colonies affected in the spring-summer season, must move them to a safe place to reduce significant loss due to depopulation. Some beekeepers have tried to reduce the loss of larvae by adding sugar syrup, reporting different results. To determine in what measure does the sugar syrup adding reduced the larvae mortality three groups of 10 colonies were installed in an apiary affected by River disease. Two of those groups were given two liters of sugar syrup 1:1 (weight:volume) in 6 opportunities throughout 19 days, one of them through an internal feeder and the other through an external feeder. The third group did not receive sugar syrup. In this period the brood’s viability was estimated four times through photographic analysis. The sugar syrup, independent of the type of feeder used, allowed 53-64% of the larvae to survive in the first week, but this values quickly decreased, reaching after 7 days a maximum of survival of 24%. These results show that the effect of the sugar syrup in the decrease of the larvae mortality is narrow and of short duration, so it is not adviced for beekeepers to resort to this handling of the colonies affected by River disease.