New Zealand’s temperate climate and bountiful flora are well suited to managed honey bees, and its geographic isolation and strict biosecurity laws have made sure that some pests and diseases affecting bees elsewhere are not present. Nevertheless, given the importance of pollination and high-value export honey to the economy, New Zealand began systematically measuring winter colony losses in 2015. The New Zealand Colony Loss Survey is modelled on the COLOSS survey but has been adapted to the New Zealand apicultural context. Some 49% of New Zealand beekeepers completed the winter 2021 survey. Between 2015 and 2021, overall colony loss rates increased monotonically from 8.37% [95% CI: 7.66%, 9.15%] to 13.59% [95% CI: 13.21%, 13.99%]. Whereas beekeepers most commonly attributed losses to queen problems between 2015 and 2020, attributions to varroa have escalated year-on-year to become the largest attributed cause of colony loss. Losses to varroa are perhaps amplified by the 23.4% of respondents who did not monitor mite loads and the 4.4% of beekeepers who did not treat varroa during the 2020/21 season. Indeed, most beekeepers consider their treatment to be effective and note that treating at the wrong time and reinvasion were major drivers of losses to varroa.

Varroa destructor is the leading cause of honey bee colony losses globally and is increasingly implicated in winter colony mortality in New Zealand. This study used data from the New Zealand Colony Loss Survey to evaluate the relationship between specific varroa management practices and over-winter colony losses among 5203 hobbyist beekeepers surveyed between 2023 and 2025. We find that beekeepers who did not treat for varroa experienced loss rates of 49.4% compared with 30.7% among beekeepers who treated. Conditional on treatment, colony losses declined as the diversity of products used increased and as treatment applications were spread throughout the year. For example, beekeepers using four or more products experienced losses of 21.2%, while those treating in three or more seasons of the year experienced losses of 24.8%. Multiple autumn treatments were also associated with lower loss rates. No statistically significant differences were observed among major treatment types when hobbyist beekeepers used a single treatment type in a single season of the year. While apiary size is negatively associated with loss rates, beekeeper experience is not. The results demonstrate that treating for varroa, product rotation, treatment throughout the year, and intensified autumn control are associated with substantially improved over-winter colony survival among hobbyist beekeepers.