Potential of bigleaf lupine for building and sustaining Osmia lignaria populations for pollination of apple

Bees of the genus Osmia Panzer (Hymenoptera: Megachilidae) are among the contenders to replace honey bees, Apis mellifera L. (Apidae), for pollinating tree-fruit crops. One species, Osmia lignaria Say, has shown great potential in western North America and was recently introduced into Nova Scotia for evaluation as a pollinator of apple, Malus Mill. (Rosaceae). A major component of that study was to develop management options for O. lignaria, including methods of sustaining nesting females following crop flowering to maximize Population recovery for pollination in subsequent seasons. The objective of this study was to evaluate bigleaf lupine, Lupinus polyphyllus Lindl. (Fabaceae), as a secondary food plant for nesting female O. lignaria by investigating nesting activity, pollen-Use patterns, and fecundity. During 2002-2003, female O. lignaria collected high proportions of apple pollen (>70%) during mid and late flowering; after then, most pollen (>90%) was collected from bigleaf lupine. The flowering period Of lupine in Nova Scotia (late May to early July) slightly overlapped that of apple, so there was no scarcity of pollen resources during the life-span of O. lignaria. Most nests typically showed high levels (<= 200%) of population growth, but recorded levels varied among nest types and locations. In 2004, nests closer to lupine plots exhibited significantly greater population recovery than nests located farther away (i.e., approximately 600 m). Bigleaf lupine is a suitable plant species for meeting the pollen requirements of nesting populations of O. lignaria following apple flowering, thus promoting the recovery of populations to meet apple pollination requirements in subsequent seasons.