Netting and pan traps fail to identify the pollinator guild of an agricultural crop

Authors: BOYER, KEVIN - Oak Ridge Institute For Science And Education (ORISE); FRAGOSO, FABIANA - Oak Ridge Institute For Science And Education (ORISE); Dieterich Mabin, Molly; Brunet, Johanne

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2020
Publication Date: 8/14/2020
Citation: Boyer, K.J., Fragoso, F.P., Dieterich Mabin, M.E., Brunet, J. 2020. Netting and pan traps fail to identify the pollinator guild of an agricultural crop. Scientific Reports. 10. Article 13819. https://doi.org/10.1038/s41598-020-70518-9.
DOI: https://doi.org/10.1038/s41598-020-70518-9

Interpretive Summary: Pollinators are in decline and pollinators affect the reproduction of many plant species. In agriculture, most fruits and vegetables need pollinators for seed production. In addition, alfalfa, a major component of the forage fed to cows and an important ingredient in chicken feed, depends on bees for seed production. The decline in pollinators is therefore expected to limit food production. Survey methods that identify the major pollinators of crop species are needed in order to quantify the impact of pollinator decline on food production. To address this need, we compared the effectiveness of two survey methods, netting and pan traps, at capturing the pollinators of alfalfa, Medicago sativa. Netting was more effective at capturing the pollinators of alfalfa. Netting captured 96% of honey bees, 94% of bumble bees, 71% of Andrena bees and 64% of Megachile bees, all known pollinators of alfalfa. However, netting and pan traps were best at capturing different bee genera. Pan traps best captured Halictus bees and bees in the Peponapis and Augochlorella genera. Within pan traps, all bees from the genera Andrena, Peponapis and Agapostemon bees were caught in blue pan traps while bees from the genus Calliopsis were only caught in white pan traps. We therefore expect the success of a survey method in identifying pollinators of a crop or plant community to vary depending on the pollinator guild. We therefore recommend using both netting and pan traps to capture bee diversity and bee richness and to identify the pollinator guild of crops and plant communities. Moreover, in order to improve the link between bee diversity, pollinator decline and food production, we suggest examining the insects caught in the nets and pan traps for the presence of pollen on their bodies and in pollen sacs. This information will benefit scientists, policy makers, farmers, the food industry and the general public interested in the impact of pollinator decline on food production.

Technical Abstract: Pollinator decline is predicted to cause significant reductions in food production and plant reproduction. Effectively monitoring demographic changes in pollinators and identifying pollinator species responsible for pollination of specific crop species, are needed in order to adequately quantify the impact of pollinator decline on food production. To address this issue, we compared the effectiveness of two survey methods, netting and pan traps, at capturing the pollinators of alfalfa, Medicago sativa. Alfalfa is a major component of the forage fed to cows and an important ingredient in chicken feed. Moreover, we examined the impact of these two survey methods on species richness and diversity and compared these measures among three colors of pan traps. Netting was more effective at capturing the pollinators of alfalfa, especially those belonging to the Bombus and Apis genera. Pan traps captured a higher bee diversity relative to netting and was also best at capturing certain bee genera. Similarly, while the three colors of pan traps captured similar bee richness and diversity, each color was most efficient for catching specific bee genera. Whether netting or pan traps best capture the pollinators of a plant species will vary with the pollinator guild of that plant species. We therefore recommend using both methods, with multiple colors of pan traps. A crucial step in these studies will be to detect pollen on the body or pollen sacs of bees and other visiting insects. Linking survey methods to pollination improves the quantification of the impact of pollinator decline on food production.