Hobby Beekeeping and Varroa – Monitor, Treat, Rotate, Repeat
Hobby beekeepers lose a disproportionate rate of colonies over winter, compared to commercial operators, the NZ Colony Loss Survey has long told us. However, that same survey shows there are some simple actions hobby beekeepers can take to help improve the chances of colony survival, explains departing survey lead Pike Stahlmann-Brown.
By Pike Stahlmann-Brown
When we open our hives each spring, I am reminded that hobbyist beekeepers carry the heaviest burden of winter losses in New Zealand. The 2025 NZ Colony Loss Survey found that beekeepers with fewer than 50 colonies lost 33.4% of their colonies over winter, compared with 13.2% for beekeepers with 50–500 colonies and 13.0% for beekeepers with more than 500 colonies. In fact, hobbyist losses have exceeded commercial losses in all of the last seven surveys, and they attribute their losses to varroa more than any other cause.
EDITOR'S SIDEBAR:
Col Loss Survey Gets a Re-brand, but Should Land Soon
For the first time in 12 years, New Zealand’s Colony Loss Survey will not be led by Bioeconomy Science Institute (formerly Manaaki Whenua Landcare Research Group) scientist Pike Stahlmann-Brown, with the Ministry for Primary Industries deciding to take the role “in-house”.
Dr Fleur Francois, Biosecurity New Zealand director, diagnostics, readiness and surveillance says they expect to distribute the survey to beekeepers in the first half of October – over a month later than recent years – with it renamed the National Bee Health Survey. Francois says that key aspects of the previous Colony Loss Survey will be retained, to support long-term trend monitoring and benchmarking.
When I presented results from the NZ Colony Loss Survey to the Wellington Beekeepers Association in spring 2024, a club member challenged me to turn the survey data into practical advice for beekeepers like her. The result is a paper recently published in the journal Insects, co-written with Ken Brown, Richard Hall, Frank Lindsay, Hayley Pragert, and Michelle Taylor.
We analysed responses from 5,203 hobbyist beekeepers who completed the NZ Colony Loss Survey in 2023, 2024, and 2025. Using multivariate regression methods, we compared winter losses across different varroa management practices while controlling for beekeeper experience, apiary size, region, and survey year. Few studies anywhere have put numbers on the benefits of varroa control in this way, and ours is the first to focus on New Zealand hobbyists. Here is what we found, and what it means in your apiary.
1. Treat. Hobbyists who did not treat for varroa lost 49.4% of their colonies over winter. Those who treated lost 30.7%. Treating is the single most important thing you can do as colonies will not simply overcome varroa on their own. This is especially true in New Zealand given our high hive density, which enables mites to move freely between apiaries.
2. Rotate products. Among beekeepers who treated, losses fell steadily as the number of different products rose: 35.5% for one product, 30.6% for two, 27.3% for three, and 21.2% for four or more. Products work in different ways, so rotating them also reduces the risk of varroa developing resistance. Alternate treatment types, avoid relying on the same product year after year, and always follow the label.
3. Treat across the year. Beekeepers who treated in only one season (a season being ‘spring’, ‘summer’, ‘autumn’ or ‘winter’) lost 35.3% of their colonies. Those who treated in three or more seasons lost 24.8%. Varroa numbers rise and fall with brood, so control is an ongoing process rather than a one-off event.
4. Make autumn count. Mite loads peak just as colonies raise the long-lived winter bees that must carry them through to spring. Beekeepers who treated more than once in autumn lost 27.5% of colonies, compared with 31.4% for those who treated once. Start early, because damage done to developing winter bees by mites and the viruses they spread cannot be undone later. And change products rather than repeating the same one.
5. Experience is no substitute for good management. Beekeepers with more than five years’ experience did not have significantly lower losses than newer beekeepers. Winter losses are not just a beginner’s problem. No two seasons are alike: weather, forage, reinvasion from collapsing colonies nearby, and mite levels all change. What worked last year may not be enough this year.
6. Monitor, don’t guess. About one in five hobbyists did no formal varroa monitoring. Deformed wings, crawling bees, and mites visible on adult bees are late signs of varroa infestation, and they often appear only after treatment can no longer save the colony. A wash with alcohol or soapy water tells you far more than a visual check, and sacrificing a sample of bees is far better than losing a colony.
A word on the evidence. Our data come from a survey, so they show correlations rather than proof of cause and effect. The NZ Colony Loss Survey is comprehensive and is answered by a large number of beekeepers, with between 29% and 43% of all registered New Zealand beekeepers taking part. The differences we found are large, and they persist after accounting for beekeeper experience, apiary size, region, and survey year. Most also held when we looked only at beekeepers who did no formal monitoring and so could not have been treating in response to monitoring results. Our results are consistent with results from field trials overseas (e.g. Kulhanek et al. 2021) .
Hobbyists lose colonies at two and a half times the commercial rate, but our results suggest that relatively modest changes can make a substantial difference. This spring, plan which products you will rotate through the year, and pencil in two autumn treatments, and monitor before and after treatment to make sure it worked.
The bottom line fits on a hive lid: Monitor. Treat. Rotate. Repeat.
Read the full article: Stahlmann-Brown et al. (2026). Varroa and Colony Losses: Practical Advice for Hobbyist Beekeepers. Insects 17(8), 870. https://www.mdpi.com/2075-4450/17/8/870
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