The density of Bombus lucorum (l.) Required to effect maximum pollination of Alfalfa in Estonia
Marika Mänd; Vambola Maavara; Ants-Johannes Martin; Raivo Mänd
Bumble bees are the most important pollinators in northern Europe, because they are the dominant taxon of a limited number of pollinator species and because they work at low temperatures (Free, 1993). To calculate the cost-effectiveness of introducing manageable pollinators, we first need to know the relationship between seed set and pollinator density. For a plant which requires cross-pollination by insects it is expected that yield increases as the number of pollinators increase, until maximum density of pollinators is reached (Dolgov & Dolgova, 1985; Richards, 1987; Richards & Edwards, 1988). Different authors give widely different estimates of the number of manageable pollinators, partly because of differences between cultivar requirements, localities, annual variation and contributions made to pollination by local wild bee populations.