Overwintering management of Osmia lignaha 



JESO Volume 139. 2008 



and Kemp et al. (2004). 



Cavity-nesting megachilid bees (Megachildae) are among the forerunners for 

 management for crop pollination (Sheffield et al. 2008) and for these species, wintering 

 in controlled climate conditions is recommended (Fairey et al. 1987; Richards et al. 1987; 

 Bosch and Kemp 2001, 2003, 2004). However, in Nova Scotia and elsewhere in North 

 America, most growers do not own or have access to controlled cold storage facilities. 

 Therefore, finding alternative methods to safely overwinter Osmia lignaria Say for orchard 

 pollination is a priority for managing this species. Considering that O. lignaria is indigenous 

 throughout temperate North America (Krombein et al. 1979) though not confirmed in Nova 

 Scotia (Sheffield et al. 2003, 2008), and that its flight period naturally corresponds with 

 flowering of many rosaceous tree fruits, it seems a reasonable assumption that this species 

 can overw inter successfully under ambient conditions within apple producing regions. 

 From 2000-2004, populations of O. lignaria were imported into Nova Scotia for evaluation 

 as a replacement pollinator for apple, and to develop region specific management strategies. 

 The objective of this study was to investigate O. lignaria winter storage options available to 

 Nova Scotia apple growers or groups interested in rearing this species for commercial tree 

 fruit pollination. Specifically, comparisons in survival and winter physiology were made 

 between O. lignaria from two populations wintered outside in a sheltered environment 

 versus in a traditional cold storage facility in the winter of 2001-2002. One population 

 consisted of the offspring of bees imported into Nova Scotia in the fall of 2000 and released 

 for pollination trials in 2001; the second was offspring of a population imported from Utah 

 following the active season of 2001. 



Materials and Methods 



Nest Preparation 



Following the active adult season (late May until early July 2001), nesting blocks 

 containing developing larvae of O. lignaria were placed in an unheated screened building 

 (insectary) maintained at the Atlantic Food and Horticulture Research Centre, Kentville. 

 Nova Scotia, to allow development to continue through to the adult stage (i.e., the wintering 

 stage) within the natal cocoons. In early autumn, samples of randomly selected nesting 

 tubes were removed from nesting blocks and split lengthwise to expose cocoons and 

 determine the number and sex of bees; caution was used to ensure the tunnel end plug 

 was left intact. Sex was determined based on cocoon size and position within the nesting 

 tube. Each cocoon was removed in sequence from the nesting tube and brushed lightly to 

 remove faecal particles and other debris. Undamaged cocoons were selected and weighed 

 to 0.00 lg, and placed into nesting tubes with the same orientation; females positioned in the 

 rear. Nesting tubes were then sealed longitudinally with masking tape. The same procedure 

 was repeated on a portion of dormant bees received from Utah in the autumn of 2001. 

 which were already split upon arrival as part of quality assessment by the supplier (Torchio 

 Enterprises, North Logan, UT). Pre-winter weights of male and female bees from both 

 locations were compared using Analysis of Variance (ANOVA). 



Samples from the two locations were divided into 24 groups (twelve each from 

 Nova Scotia and Utah), each group having at least 20 females among the nesting tubes. The 



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