Pesticide and resource stressors additively impair wild bee reproduction

Bees and other beneficial insects experience multiple stressors within agricultural landscapes that act together to impact their health and diminish their ability to deliver the ecosystem services on which human food supplies depend. Disentangling the effects of coupled stressors is a primary challenge for understanding how to promote their populations and ensure robust pollination and other ecosystem services. We used a crossed design to quantify the individual and combined effects of food resource limitation and pesticide exposure on the survival, nesting, and reproduction of the blue orchard bee Osmia lignaria . Nesting females in large flight cages accessed wildflowers at high or low densities, treated with or without the common insecticide, imidacloprid. Pesticides and resource limitation acted additively to dramatically reduce reproduction in free-flying bees. Our results emphasize the importance of considering multiple drivers to inform population persistence, management, and risk assessment for the long-term sustainability of food production and natural ecosystems.

Assessing blue orchard bee (Osmia lignaria) propagation and pollination services in the presence of honey bees (Apis mellifera) in Utah tart cherries

Osmia lignaria is a commercially available, native solitary bee species recognized for its propensity to forage upon and pollinate tree fruit crops such as apple, almond and cherry. This study evaluated the implementation of O. lignaria co-pollination with honey bees in central Utah commercial tart cherry orchards during 2017 and 2018 bloom. Three paired 1.2 ha sites were selected for evaluation of cherry fruit set and yield with and without managed O. lignaria releases alongside the standard honey bee hive stocking rate of 2.5 hives/ha. Osmia lignaria supplementation did not measurably increase cherry fruit set, fruit per limb cross-sectional area or fruit weight. The lack of differences in yield is likely a consequence of local saturation of pollinator services supplied by managed honey bees throughout experimental orchards, such that no additive benefit of managed O. lignaria releases were measurable. An increase in managed O. lignaria populations was achieved in 2017 but not 2018, possibly due to unknown changes to orchard management or environmental factors. While flying O. lignaria in Utah tart cherries may support sustainable in-field bee propagation, their subsequent impacts on tart cherry yield were not detected when paired with standard stocking densities of honey bees.

Blue Orchard Bee, Osmia lignaria Say (Insecta: Hymenoptera: Megachilidae)

The blue orchard bee, Osmia lignaria Say (Fig. 1), is a solitary mason bee native to the west coast of the United States and Canada. It is of great interest for use as a native pollinator of fruit trees and blueberries, and is easily managed due to its favorable biological characteristics. Blue orchard bees can be purchased online for pollination, and they are shipped as pupae ready to emerge in the spring. This 4-page fact sheet was written by Alden Estep, Catherine Zettel-Nalen, and James Ellis, and published by the UF Department of Entomology and Nematology, March 2013. http://edis.ifas.ufl.edu/in982