Fig 1.
Number of live colonies in total and by apiary (location and wintering method) over 23 months with x-axis breaks with vertical lines indicating winter.
Fig 2.
Influence of geographic location on average Nosema abundance over 23 months.
North represents colonies near Edmonton and South represents colonies near Rainier. Data are plotted as untransformed means. Dashed line shows the 1 million spores/bee nominal threshold. Asterisks indicate significant differences (P <0.05, Slice) between locations within dates.
Fig 3.
Influence of wintering method on average Nosema abundance over 23 months.
Indoor represents colonies moved to an indoor wintering building, and outdoor represents colonies kept outdoors in insulating wraps. Data are plotted as untransformed means. Dashed line shows the historical 1 million spores/bee nominal threshold.
Fig 4.
Influence of wintering method on average adult bee population (live colonies) over 23 months.
Indoor represents colonies moved to an indoor wintering building, and outdoor represents colonies kept outdoors in insulating wraps. Asterisks indicate significant differences between wintering methods.
Fig 5.
(A) The effect of average Nosema abundance in the previous summer (July-August, 2017) on the predicted probability of having dead colonies in spring 2018 (cumulative colony mortality on April 25, 2018). (B) The effect of average Nosema abundance in the previous spring (April—June, 2018) on the predicted probability of having dead colonies in spring 2019 (cumulative colony mortality on April 5, 2019). Shaded area is the 95% confidence limit. Dashed line shows the 1 million spores/bee nominal threshold. The circles indicate whether colonies were alive (0) or dead (1) at a specific Nosema abundance.
Fig 6.
The effect of wintering method on the predicted probability of observing dead colonies at the end of 23 months (cumulative mortality at the end of the study) as influenced by the average Nosema abundance over the study (June 2017-September 2018).
Indoor represents colonies moved to an indoor wintering building, and outdoor represents colonies kept outdoors in insulating wraps. Dashed line shows the 1 million spores/bee nominal threshold. The symbols indicate whether colonies were alive (0) or dead (1) at a specific Nosema abundance within wintering method. Samples of dead bees taken from the bottom board (due to the unavailability of live bees in the colony) are included in the average.
Fig 7.
The effect of two-year average spring Nosema abundance over the study (June 2017, April-June 2018) on the predicted probability of observing dead colonies at the end of 23 months (cumulative mortality at the end of the study).
Shaded area is the 95% confidence limit. Dashed line shows the 1 million spores/bee nominal threshold. The circles indicate whether colonies were alive (0) or dead (1) at a specific Nosema abundance. Samples of dead bees taken from the bottom board (due to the unavailability of live bees in the colony) are included in the average.