Chapter 4: The Development of <i>Osmia lignaria</i> Say (Hymenoptera: Megachilidae) as a Managed Pollinator of Apple and Almond Crops: A Case History

Abstract

<i>Agronomic practices in monocultural apple and almond orchards have changed pollination requirements, creating a need for additional pollinator species. The blue orchard bee</i>, Osmia lignaria <i>Say, has been studied as a candidate pollinator after a survey of</i> Prunus <i>and</i> Malus <i>spp. flowers revealed that this bee was omnipresent. The nesting success of</i> O. lignaria <i>populations introduced into commercial apple and almond orchards depends on acceptance and successful use of man-made nesting units that have been designed so that natal nests can be removed easily, examined to control nest associates, and reused in subsequent years. Dispersal of large numbers of bees before nesting was resolved when some natal nests were inserted into nest units placed in the field, or when some bees were released in the field early and the largest number of bees were released soon afterward. Blue orchard bees absconded when small nest structures were moved. However, nesting populations in large nest shelters were successfully moved &gt;0.40 km at night to new pollen-nectar resources. The blue orchard bee was shown to be an outstanding pollinator in several interrelated studies in commercial almond and apple orchards. When orchards were overpopulated with this mason bee, insufficient quantities of pollen and nectar resources, and the construction of fewer, smaller provisions with less nectar, led to smaller bees, more males, and high immature mortality due mostly to eggs detaching from dry cell provisions. Winter storage at 3 °C for 220–260 d was optimal for predictable emergence of vigorous bees. Finally, many of the most important nest associates were controlled when thick-walled nesting tubes prevented successful oviposition by these parasites. This long-term research program has led to workable and practical bee management systems for apple and almond production</i>.