Associations were calculated treating each hive sample at each time-point as a distinct event. P-values (Chi-square values) and odds ratios (OR) listed were calculated by the OpenEpi statistical package v2.3 (http://www.openepi.com/OE2.3/Menu/OpenE-piMenu.htm). Only seven microbes with incidences in the study set of at least 10% (20 incidences in 197 samples) were examined for association, resulting in 28 discrete association tests and the corresponding Bonferroni multiple testing correction. Microbes occurring infrequently were not used in association tests and so did not contribute to multiple testing correction.