Priority Researches Needed With Solitary Bees To Make Possible Their Large-Scale Use As Pollinators In Agricultural Settings

Breno Magalh„es Freitas
Universidade Federal do Ceará- Brazil

Around 85% of the 20,000 known bee species of the world are solitary and most of the natural pollination occurring in wild and agricultural settings comes from their activities. For a long time the role of solitary bees in pollinating agricultural crops was ignored and their importance as pollinators was emphasised mainly to wild plant species. Over this time, honey bees (Apis mellifera) were the solely pollinator used to increase pollination of crops. Recently, it was realised that other bee species could be as efficient pollinators as honey bees and, for certain crops, even more efficient than A. mellifera.

Researches carried out investigating non-Apis pollinators have shown a series of examples of crops in which solitary bee species are better pollinators than honey bees, such as Megachile rotundata and Nomia melanderi in alfalfa (Medicago sativa), Peponapis pruinosa in pumpkin (Curcubita pepo), Osmia rufa in apple (Malus domestica), Osmia cornifrons in strawberry (Fragaria x ananassa), Xylocopa spp. in passionfruit (Passiflora edulis), etc. In Brazil, some of the solitary bees confirmed as efficient pollinators are Centris tarsata in cashew (Anacardium occidentale), C. tarsata and C. aenea in West Indian cherry (Malpighia emarginata), C. tarsata and C. bicolor in "murici" or wild cherry (Byrsonima crassifolia), Xylocopa frontalis in guava (Psidium guajava), Eulaema spp. in Brazil nut (Bertholletia excelsa).

However, natural populations of these species in agricultural areas are small and their numbers are dwindling faster as intense agricultural practices grows and affects negatively their habitats. Presently, except for the case of M. rotundata, solitary bees are not readily available in large numbers for introduction in cropped areas as pollinators.

Much research is needed to make possible large-scale use of solitary bees as pollinators in agricultural areas. The challenges are (i) to investigate other potentially good pollinator species and to define their pollination efficiency. Then, (ii) to study biology, especially topics such as nesting biology and requirements, reproductive strategies, annual cycle(s) and parasitism, to each selected bee species. Based upon the information gathered in these studies, it will be necessary (iii) to develop artificial nests and/or to create adequate conditions to stimulate spontaneous nesting, reproduction and foraging of the bee species on the target crop. Finally, depending on the bee species, (iv) development of management techniques will be necessary to direct to or to maintain bees on the target crop, to achieve an even bee distribution on the area and to maximise pollination efficiency of the flowers.

To turn pollination with solitary bees a common practice in agricultural settings will be a long and defying process, but it can also be fascinating and much rewarding. The bees are out there awaiting for us, hands to work!!

Edited from the article Identifying and using solitary bees for pollination of tropical crops written by Breno M. Freitas and José Everton Alves and available at the homepage of the Bee Research Group of Universidade Federal do Ceará (