Consequences of parental origin on development and survival of Osmia lignaria reared in California almond orchards

The blue orchard bee, Osmia lignaria, is a solitary cavity-nesting bee and effective pollinator of fruit trees. To acquire stocks of O. lignaria for pollination, trap-nesting has traditionally been done in Washington and Utah. Management protocols are needed for bees originating from Washington and Utah where overall climate is cooler compared to central California where the bees are used in February for almond pollination. To evaluate climatic adaptations of O. lignaria relevant to their management, we released in separate orchards trap-caught O. lignaria adults from California, Washington, and Utah. Freshly completed nests were shipped to the laboratory for continued development in an incubator set for 10-year average Stockton, CA temperatures. We monitored developmental rates and survival of these offspring to adulthood. Prepupal duration for Washington and Utah progeny was half that of the California progeny. Washington and Utah progeny also became adults in the summer about two weeks prior to the California progeny. Left at ambient California conditions (i.e., no management) after adults had formed in the cocoon in the summer until adult emergence the following spring, survival of the Washington and Utah progeny was 25% and 21% respectively; survival of California progeny was 86%. Survival of Utah and Washington progeny managed using pre- and overwintering regimes were at least 90% and 81%, respectively; survival of managed California progeny was 73%. Accommodating regional thermal adaptations (i.e. region-defined developmental rates) will be critical to successful management of this bee for almond pollination.