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Anno 2 N. 2
Bettina Maccagnani [1], Antonio Felicioli [2]

Rearing and using bees : solving the problems and finding new perspectives

[1] DiSTA - Area Entomolgia, Università di Bologna, Italy
[2] Dip. Anatomia, Biochimica e Fisiologia veterinaria, Università di Pisa, Italy


Corresponding author: bmaccagnani@entom.agrsci.unibo.it

Entomophilous pollination is of critical importance in maintaining population diversity among the wild vegetation, and in ensuring high qualitative and quantitative standards of 75% of the main cultivated plant species around the world.
The main criteria to choose the best species for developing a rearing system focus on plant-insect interactions (synchronicity between target crop flowering period and bee flight period; proper relative dimension of the flower and the insect; correspondence between the resources offered by the flower and the need of the bee) and on the biological and ethological traits of the wild bee specie finalized to the development of productive mass rearing and to the management of the population (diapause, acceptation of artificial nests, social or gregarious nesting behaviour).

In North America and Japan various species of wild pollinators of the Megachilidae family, as Megachile rotundata and Nomia melanderi since many years are reared and use on the large scale for alfalfa pollination, and only in Canada their contribute to seed production is estimated in 6 million Canadian dollars per year.

Several specie of the genus Osmia, are reared both in North America and Europe for early fruit crop berry pollination. For all megachilid species a rearing system is not available yet. The main problems: the necessity of long flights for the males, the necessity of UV light during mating, the difficulty of furnishing pollen in a way suitable for being collected by the female, or, in case of oviposition on larval artificial diet in capsules, the diet composition, which requires more than pollen and nectar as ingredients (mother addictives and/or essential oils). The rearing is made mainly with the releasing and rearing technique in natural environment, or combining it with the pollination service.

In this case the flowering of the target crop has to be long enough or supplementary food resources has to be provided adding flower strips, of combining multi-crop cultivation in order to allow females to complete their reproductive period. The release of megachilid bees in confined environment can be a good way to provide pollination service, reproduce the population and avoid parasitoid impact, even though it has to be preliminarily decided which balance to choose between maximizing the pollination service or the reproduction of the population, from which depends the number of female to be released per square meter of crop.

The ease of adaptation to confined environments constituted one of the reason of the success of the development rearing systems for Bombus spp. species (one million colonies commercialised per year); five species are involved, all pertaining to the so-called “pollen storer” group, because it is easy to furnish pollen in the rearing box in captivity. Many difficulties have been over-passed in these years (mating, diapause and hibernation management, colony foundation and indoor new queen production) and now the breeding companies can produce colonies with high quality standard characteristics, suitable for crops with different requirements. The necessity of buzz pollinate several crops without introducing the reared Bombus spp. species in areas of the world in which they are not naturally present prompted the search for new local pollinator species to be searched among both solitary and social species. This process is under development in several part of the world, mainly in the tropics (where the aim is also to preserve biodiversity of wild flora) and in Australia,. Research on rearing possibility for Xylocopa spp (carpenter bees) and Amegilla spp. (ground nesting bees), whose effectiveness in buzz pollinating tomatoes under confined environment has been already assessed, gained already very important results.

A new perspective in the use of pollinators is the possibility to employ them in the distribution of useful microbial agent for the microbiological control of plant pathogen whose primary way of penetration in the plant is though the flower organs: combining this service with the pollination service could result in a very productive positive synergy.