ARS | Publication request: Field use of an incubation box for improved emergence timing of Osmia lignaria populations used for orchard pollination

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 24, 2007
Publication Date: February 12, 2008
Citation: Pitts Singer, T., Bosch, J., Kemp, W.P., Trostle, G.E. 2008. Field use of an incubation box for improved emergence timing of Osmia lignaria populations used for orchard pollination. Apidologie. 39: 235-246

Interpretive Summary: The blue orchard bee, Osmia lignaria Say, is a cavity-nesting solitary bee that is native to North America and is an efficient pollinator of orchard flowers. Blue orchard bees spend the winter as adults in their cocoons, and when exposed to warm spring temperatures, will emerge within a few days and take flight. With proper management, blue orchard bee populations can be sustained and increased. One problem with using blue orchard bees for orchard pollination is that fruit trees bloom early in the spring when temperatures can still be cool enough to inhibit bee activity, and our study addresses this problem. We performed field tests of an outdoor, incubation box. The main objective was to compare emergence rates of bees incubated in incubation boxes with bees incubated under ambient conditions in wood blocks, and to ascertain whether faster bee emergence can be obtained without increasing mortality. A second objective was to compare bee emergence rates out of individual cocoons with emergence rates out of natal nests. Our results show that the incubation box is an effective tool for shortening emergence periods and, therefore, improves management of these bees as crop pollinators, especially when weather is variable and unpredictable.

Technical Abstract: Wintered populations of blue orchard bees, Osmia lignaria, require incubation for prompt emergence. In this study, bee nests were placed in an almond (California) and an apple (Utah) orchard under two incubation treatments: in wood blocks and in incubation boxes. Individual cocoons were also placed in boxes. Incubation boxes had heating units (set to max. temperature = 22C) to increase or prolong daytime temperature to higher than ambient (>14C higher in UT). Bee emergence was monitored, and temperatures were recorded. Heated boxes were allowed for faster accumulation of heat units compared to blocks. Bees survived well under all conditions(>90% emergence). Compared to bees in wood blocks, bees in boxes required one day less in CA and several days less in Utah for 100% female emergence. Results show the utility of heated incubation boxes for shortening O. lignaria emergence time, helping to synchronize bee emergence with bloom initiation.