Regionally adapted developmental eco-physiology of Osmia lignaria: Management implications for almond pollination

Pollination of an early-blooming spring crop such as almonds requires pollinators to be ready for flight unnaturally early, often during inclement weather. Properly managed, the solitary, cavity-nesting bee Osmia lignaria (blue orchard bee) can be readied for emergence and release in blooming almond orchards. Currently, commercial populations of O. lignaria are unavailable, and populations used for orchard pollination are trapped from natural areas of Utah, Washington, and recently, California. We studied bee populations from those three geographic sources to evaluate and compare: 1) survival, emergence timing, and emergence synchrony after adult winter diapause at different temperatures and durations and 2) developmental progress and summer diapause of progeny of the three parental populations reared at hourly California temperatures. Results show regional population differences for both wintered adults and progeny reared under California temperatures. If un- or improperly managed during critical life stages, O. lignaria populations obtained from different regions will suffer high mortality when produced for early-blooming (or other) crops for whose regional conditions bees are not climatically adapted. Our findings suggest practical management and mass-production protocols (and harmful practices to avoid) through better understanding of the basis for phenotypic differences in the eco-physiology of O. lignaria populations adapted to regional climates.