Examination of a managed pollinator strategy for almond production using Apis mellifera (Hymenoptera: Apidae) and Osmia lignaria (Hymenoptera: Megachilidae)

Authors: Pitts Singer, Theresa; ARTZ, DEREK - Former ARS Employee; PETERSON, STEPHEN - Foothill Bee Ranch; Boyle, Natalie; WARDELL, GORDON - Wonderful Orchards

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2018
Publication Date: 2/17/2018
Citation: Pitts-Singer, T., Artz, D.R., Peterson, S.L., Boyle, N.K., Wardell, G.I. 2018. Examination of a managed pollinator strategy for almond production using Apis mellifera (Hymenoptera: Apidae) and Osmia lignaria (Hymenoptera: Megachilidae). Environmental Entomology. 47(2):364-377. https://doi.org/10.1093/ee/nvy009.
DOI: https://doi.org/10.1093/ee/nvy009

Interpretive Summary: Pollination services provided by managed bees are essential for California almond production. Currently, pollination needs are met by rented or owned colonies of honey bees. Excessive demand on a challenged honey bee industry to provide strong colonies in early spring has caused sharp increases in rental prices over the past decade, inviting the consideration of alternative pollinators in addition to honey bees. The blue orchard bee is an excellent pollinator of fruit and nut trees, but its effects when partnered with honey bees have yet to be evaluated in large, commercial almond orchards. A two-year study was conducted in California orchards to compare almond pollination and production using the standard practice of honey bees as a lone pollinator to an alternative practice of co-pollination using honey bees plus blue orchard bees. On account of local weather, orchard management varies between almond growing regions, such as use of pesticides and irrigation options. Therefore, both north-central and southern regions of California’s San Joaquin Valley were represented in this study. We examined bee visitation, nut set, and nut yield between orchards and between tree rows within orchards. Also, the ability of blue orchard bees to successfully reproduce was recorded to make sure that these bees remained in the orchards as pollinators and to assess the ability to sustain these bees under regional orchard conditions. We demonstrate that supplying large commercial almond orchards with honey bees plus blue orchard bees can significantly increase nut set. Nut yield is more variable, dependent upon additional factors such as water availability.

Technical Abstract: Pollination services provided by managed bees are essential for California almond (Prunus dulcis Mill.) production. Currently, pollination needs are met by rented or owned colonies of honey bees (Apis mellifera L.). Excessive demand on a challenged A. mellifera industry to provide strong colonies in early spring has caused sharp increases in rental prices over the past decade, inviting the consideration of alternative pollinators in addition to A. mellifera. The blue orchard bee, Osmia lignaria Say, is an excellent pollinator of fruit and nut trees, but its effects when used in tandem with A. mellifera have yet to be evaluated in large, commercial almond orchards. A two-year study was conducted in California orchards to compare almond pollination and production using the standard practice of A. mellifera as sole pollinator to an alternative practice of co-pollination using A. mellifera in addition to O. lignaria. On account of local climates, orchard management varies between almond growing regions, such as use of pesticides and irrigation options. Therefore, both north-central and southern regions of California’s San Joaquin Valley were represented in this study. We examined bee visitation, nut set, and nut yield between orchards and between tree rows within orchards. Also, O. lignaria reproductive success was recorded to assure that these bees remained in the orchards as pollinators and to assess the ability to sustain these bees under regional orchard conditions. We demonstrate that augmenting large commercial almond orchards with O. lignaria can significantly increase nut set and sometimes nut yield in both regions evaluated.