Preliminary observations of Osmia coerulescens as a pollinator of herbage seed crops

Abstract

The availability of large numbers of pollinators is critical to the efficient seed production of crosspollinated species of herbage legumes. The honey bee is the predominant pollinator of crops in New Zealand. There are risks in being solely dependent on the honey bee for pollination. Honey bee diseases and mites have reduced bee numbers in many parts of the world. The floral morphologies of some species such as tetraploid red clovers and lucerne are unsuited to pollination by honey bees. Other than in some localised areas, alternative pollinators have had little impact on improving pollination of these species in New Zealand. In 1995, Osmia coerulescens L. was introduced into New Zealand to be evaluated as an alternative, managed pollinator for herbage seed crops. Results from the 1997/98 season show that O. coerulescens can be stored at 2-3°C with low mortality until the bees are 9 months old. When stored to 10.5 months of age, reproductive vigour was lost and mortality was high. The potential multiplication rate of this bee is high, especially in the first generation of a season. Managing the bees to emerge during summer rather than spring as occurs naturally had no effect on bee reproduction. The bee also successfully reproduced when retricted to white clover flowers as the only source of pollen and nectar. The wasp parasitoid Melittobia spp. destroyed large numbers of developing bees resulting from the nesting of 2nd-generation bees. Control of Melittobia spp. is discussed. Keywords: management, Melittobia spp., Osmia coerulescens, pollination