According to the 2025 New Zealand Colony Loss Survey, varroa mites emerged as the most significant cause of colony losses.
Varroa are external parasites that feed on adult honeybees and infect bee larvae as they develop.
Severe infestations weaken individual bees, transmit diseases, and can ultimately cause the collapse of entire colonies.
Losses attributed to varroa and related complications reached their highest level since the survey began in 2015.
An estimated seven per cent of all healthy, living colonies dying over winter resulting from what beekeepers identified as varroa and related complications.
There were more losses to varroa than to queen problems, suspected starvation, wasps, and all other causes combined.
Bee colonies were particularly susceptible in the lower South Islands, with higher losses attributed to varroa.
The survey estimated that approximately 63,435 colonies died over the winter period in New Zealand.
The loss rate represented an increase compared with recent years, reversing the trend of declining winter losses that had been observed previously.
However, the survey noted that losses still remain below the peak recorded in 2021.
Geographically, colony losses were not evenly distributed with the highest loss rates recorded in the lower South Island.
This indicated persistent regional pressures on colony survival.
Wasp controls working
The 2025 survey also focused how beekeepers were controlling wasp populations.
Wasps are known predators of bees and competitors for food resources, and their control can indirectly support colony health.
The survey found that 49 per cent of beekeepers actively controlled wasps.
Among those who did so, around half reported using traps as a control method.
A further 41 per cent directly destroyed wasp nests, while 33 per cent reported indirectly killing wasp nests, such as through baiting or other control strategies. Some beekeepers used more than one method.
Based on survey responses, researchers estimate that beekeepers collectively killed approximately 12,200 wasp nests over the past year.
The control of the wasp population has benefits that go beyond bee colonies, as wasps can cause substantial environmental and economic damage if left unchecked.
A nationwide assessment
The New Zealand Colony Loss Survey was conducted by researchers at the Bioeconomy Science Institute Maiangi Taiao.
It provided a nationwide assessment of honeybee colony health and winter survival.
The survey was based on an international standard developed by the COLOSS honeybee research association and was designed to track colony loss rates and key stressors affecting beekeepers.
The latest results relate to winter 2025 colony losses and were released on April 2, 2026.
In 2025, the survey collected responses from 1,948 beekeepers managing a combined total of 148,460 colonies.
The data was used to estimate losses across the country’s total colony population, which was estimated at 495,587 colonies.
