Abstract
We describe augmentation of managed populations of Osmia cornuta and O. rufa in the vicinity of Belgrade (Serbia). Annual augmentation of O. cornuta populations was more than five-fold during the six years of our study. This was achieved by watering the soil near the Osmia augmentation shelters used for nest building. However, populations of O. rufa under the same treatment only doubled annually. Data are also presented on sex ratios in these managed populations, the sex ratio being an important factor in increasing population numbers and raising pollination efficacy. Sex ratio values (♂ : ♀) varied from 1.46 : 1 to 3.22 : 1 in the populations of O. cornuta and from 1.35 : 1 to 2.68 : 1 in those of O. rufa.
Highlights
A number of species of orchard bees are used commercially as pollinators in many countries
We describe augmentation of managed populations of Osmia cornuta and O. rufa in the vicinity of Belgrade (Serbia)
Data are presented on sex ratios in these managed populations, the sex ratio being an important factor in increasing population numbers and raising pollination efficacy
Summary
A number of species of orchard bees are used commercially as pollinators in many countries. Previous to the current study, we attempted to augment Osmia cornuta and O. rufa populations in orchards. Even though we carefully selected such places over a long period of time (several years), we did not succeed in increasing the population to a level higher than about 50,000. It seemed at the time that dispersion of females was a significant constraint on population during this period (Bosch, 1994; Kruniü et al, 2001). We chose to test this assumption by studying augmentation of O. cornuta and O. rufa in the vicinity of Belgrade (Serbia) by examining whether, alternatively, the sex ratio of both species in the managed populations is a factor important for augmentation
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