Improving Osmia lignaria and O. cornifrons (Hymenoptera: Megachilidae) retention with preferred nest materials and attractant spray

Authors: PINILLA-GALLEGO, M - North Carolina State University; ROWE, LOGAN - Michigan State University; GIBBS, JASON - University Of Manitoba; Pitts Singer, Theresa; ISAACS, RUFUS - Michigan State University

Submitted to: Journal of Applied Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2022
Publication Date: 4/7/2022
Citation: Pinilla-Gallego, M.S., Rowe, L.M., Gibbs, J., Pitts Singer, T., Isaacs, R. 2022. Improving Osmia lignaria and O. cornifrons (Hymenoptera: Megachilidae) retention with preferred nest materials and attractant spray. Journal of Applied Entomology. 146(6):743-752. https://doi.org/10.1111/jen.13001.
DOI: https://doi.org/10.1111/jen.13001

Interpretive Summary: Osmia bees are alternative managed pollinators with the potential to be added pollinators along with honey bees in many crops. However, challenges for their management in orchards still remain. Female bees will leave nesting sites if nesting materials and attractiveness are not ideal, which makes commercial management less profitable. One way to help keep female bees from flying away is to make nesting sites more attractive. We tested the effect of several combinations of nesting materials and shelter types, as well as an attractant compound, to see which materials were most acceptable to blue orchard bees and Japanese orchard bees (two managed pollinating bee species) and promoted high bee reproduction. We compared nesting in shelters of three different colors, with paper tubes of four different diameters, reeds, and wood blocks as nesting materials at an experimental farm orchard. In a separate experiment with a standard shelter and material, we tested an attractant spray based on a compound discovered from blue orchard bee cocoons to encourage females to nest in the same cavities from where they emerged. In both experiments, the Japanese orchard bee females were more likely to nest in any of the materials offered compared to the blue orchard bees. Wood shelters with reeds was the shelter/material combination with the highest nesting for both species, although Japanese orchard bees also used paper tubes of 5-6 mm diameter. The attractant spray increased nesting by Japanese orchard bees, but not by blue orchard bees. We also found that weather and other environmental variables probably affected the potency of the attractant. Together, our results suggest that using the right combination of shelters and materials, as well as the attractant spray, is an effective strategy to increase Osmia female retention for orchard pollination.

Technical Abstract: Osmia bees are alternative managed pollinators with the potential to supplement pollination by honey bees in many crops. However, challenges for their management in orchards still remain. If nesting conditions are not optimal, females can show high dispersion rates, which make their implementation at commercial scales less economically viable. One way to improve female retention is by offering more attractive nesting substrates. We tested the effect of several combinations of substrate materials and shelter types, as well as an attractant compound, on the retention and female performance of Osmia lignaria and O. cornifrons females, two species used for orchard pollination in the US. We compared nesting in shelters of three different colors, with paper tubes of four different diameters, reeds, and wood blocks as substrates at an experimental farm orchard. In a separate experiment with a standard shelter and substrate, we tested an attractant spray based on a compound isolated from O. lignaria cocoons to encourage females to nest in the same cavities from where they emerged. In both experiments, O. cornifrons showed higher female retention than O. lignaria. Wood shelters with reeds was the shelter/substrate combination with the highest nesting for both species, although O. cornifrons also used paper tubes of 5-6 mm diameter. The attractant spray increased nesting by O. cornifrons, but not by O. lignaria. We also found a significant interaction between the effect of the attractant and the year of the experiment, indicating that weather and other environmental variables can affect the efficacy of the attractant. Together, our results suggest that using the right combination of shelters and substrates, as well as the attractant spray, is an effective strategy to increase Osmia female retention for orchard pollination.