Influence of nest box color and release sites on Osmia lignaria (Hymenoptera: Megachilidae) reproductive success in a commercial almond orchard

Authors: Artz, Derek; ALLAN, MATTHEW - Pacific Pollination, Llc; WARDELL, GORDON - Paramount Farming Company, Inc; Pitts Singer, Theresa

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2014
Publication Date: 12/4/2014
Citation: Artz, D.R., Allan, M.J., Wardell, G.I., Pitts Singer, T. 2014. Influence of nest box color and release sites on Osmia lignaria (Hymenoptera: Megachilidae) reproductive success in a commercial almond orchard. Journal of Economic Entomology. 107:2045-2054.

Interpretive Summary: Commercial agriculture in the US relies heavily on large numbers of honey bees to pollinate many important crops, including almonds, cherries, and blueberries, but because of the reduced availability of honey bee colonies and high honey bee rental costs, alternative pollinators could provide a pollination insurance against ongoing honey bee losses. Previously, we studied the impact of two nesting site density treatments (different numbers of boxes and cavities per box) on how well blue orchard bees could find the nests and use them for making offspring in a 151 acre California almond orchard pollinated by a mixture of blue orchard bees and honey bees. In two new separate experiments in the same orchard, we 1) further investigated the effects of four nesting site densities as well as color of nest boxes, and 2) the number of sites from which bees are released into the orchard on blue orchard bee reproduction and almond yield. In the nesting site density and nest box color experiment, the number of nests, number of cells, and number of male and female cells produced by nesting blue orchard bee females were greatly influenced by the number of available cavities within nest boxes and nest box color. Blue orchard bees had better reproduction in light blue nest boxes followed by red nest boxes and then yellow nest boxes. However, neither nesting site density nor nest box color influenced the number of nuts produced or total nut weight. Results from the nesting site density and bee release site experiment showed that more nests, cells, and male and female cells were produced in high density (low cavity) nest boxes compared to low density (high cavity) nest boxes, but there were no significant differences in the number of nests between one and 15 release sites. Blue orchard bee foraging and nesting activity influenced nut yield by producing more nuts in orchard areas with high density nest boxes with one release site compared to either low density nest boxes with one release site or high density nest boxes with 15 release sites. This study shows that number of nest boxes and cavities per box as well as the color of nest boxes, but not the number of bee release sites, can greatly affect where these pollinating bees make nests and if they produce many offspring in those nests in a large commercial almond orchard.

Technical Abstract: Because of the reduced availability of honey bee (Apis mellifera) colonies for commercial pollination and high honey bee rental costs, alternative pollinators could provide pollination insurance against ongoing honey bee losses. In 2011, we studied the impact of two nesting site density treatments (different numbers of boxes and cavities per box) on the reproductive success of mass-released blue orchard bee (Osmia lignaria) adults in a 151 acre California almond orchard pollinated by a mixture of O. lignaria and A. mellifera. In 2012, using two separate experiments in the same orchard, we 1) further investigated the effects of nesting site density as well as color of nest boxes, and 2) the number of bee release sites on O. lignaria nest box utilization, reproductive success, and almond nut yield. In the nesting site density and nest box color experiment, the number of nests, number of cells, and number of male and female cells produced by O. lignaria females was greatly influenced by the number of available cavities within nest boxes and nest box color. Most measures of O. lignaria reproductive success were greater in light blue nest boxes followed by red nest boxes and than yellow nest boxes. However, neither nesting site density nor nest box color influenced the number of nuts produced or total nut weight. Results from the nesting site density and bee release site experiment showed that more nests, cells, and male and female cells were produced in high density (low cavity) nest boxes compared to low density (high cavity) nest boxes, but there were no significant differences in the number of nests between the bee release site treatments (i.e., one and 15 release sites). O. lignaria foraging and nesting activity influenced nut yield by producing more nuts in orchard areas with high density nest boxes with one release site compared to either low density nest boxes with one release site or high density nest boxes with 15 release sites. This study shows that density of nest boxes and the color of nest boxes, but not the number of bee release sites, can greatly affect nest establishment and reproductive success of O. lignaria in a large commercial almond orchard.