Ontario’s 2025 winter-loss numbers brought some relief, but not comfort.
After the severe losses reported for the 2023–2024 winter, Ontario beekeepers saw improvement during the 2024–2025 season. The province’s official apiculture winter loss report estimated 37% overwinter mortality for commercial beekeepers, down from 50% the year before. Small-scale beekeepers were estimated at approximately 43% winter loss, meaning smaller operations still lost colonies at a higher rate than commercial operators.
That is progress. But it is not a good number.
A 37% winter loss means more than one out of every three colonies is dead or non-viable by spring. For a beekeeper with 100 colonies, that is 37 colonies gone before the season begins. For someone with two hives in the backyard, losing one colony is a 50% loss. Losing both means starting over completely.
The Ontario Beekeepers’ Association reported a similar pattern in its 2025 Winter Loss Survey. In spring 2025, 642 Ontario beekeepers reported on 27,465 colonies that had gone into winter in fall 2024. The survey found an average winter loss of 33.5% and a median loss of 36%. It also reported an additional 8.8% average in-season loss, bringing the total reported loss over the previous beekeeping year to 39.3%.
That last number matters. Winter loss gets most of the attention, but colonies can also fail before they ever reach winter. A colony that collapses in late summer or fall may never be counted as a winter dead-out, but it still represents the same thing to the beekeeper: lost bees, lost production, lost time, and another unit that has to be rebuilt.
Better than last year does not mean sustainable
It is tempting to treat the 2025 numbers as good news because they improved from the year before. In one sense, they are good news. A drop from roughly 50% to 37% commercial overwinter mortality is meaningful. It means more colonies survived, more equipment went into spring with bees in it, and fewer beekeepers were facing the worst-case scenario.
But a loss rate in the mid-30% range is still not where the industry wants to be.
Ontario’s own historical winter-loss reports reference 15% overwinter loss as the maximum level generally considered acceptable and sustainable by the Canadian beekeeping industry. By that standard, Ontario’s 2025 losses were still more than double the sustainable benchmark.
That is the point new beekeepers need to understand. The headline is not “everything is fine now.” The real message is:
Ontario losses improved, but beekeeping remains under heavy biological and management pressure.
The losses are not evenly distributed
The provincial average hides a major difference between operation sizes.
Ontario’s 2025 report showed winter mortality ranging from 32.5% to 50.0% depending on operation size. Small operations were hit hardest: beekeepers with fewer than 10 colonies reported 50.0% winter mortality, while operations with 10 to 49 colonies reported 41.8%. The lowest reported mortality was in the 201 to 500 colony group at 32.5%.
The OBA survey showed the same pattern. Beekeepers with fewer than 50 hives reported an average winter loss of 40.5%, while beekeepers with at least 50 hives reported an average loss of 31.8%. The survey also found that 64.3% of respondents reported winter losses over 20%.
That does not mean small beekeepers are careless. Many are careful and skilled. But small operations often have less margin. They may have fewer spare queens, fewer strong colonies to equalize from, less drawn comb, less disease experience, and fewer opportunities to compare what is normal across many colonies.
A commercial beekeeper can lose colonies and still have surviving stock to split, boost, combine, or requeen from. A two-hive beekeeper who loses one colony has very few options left. Scale does not make bees healthier by itself, but it gives the beekeeper more management flexibility.
What actually kills colonies?
The frustrating answer is that winter loss is usually not one thing.
Ontario’s official report lists several suspected contributors: Varroa mites and associated viruses, climate and weather, weak colonies in the fall, poor queens, starvation, and pesticide or environmental chemical exposure. The OBA survey reported the top three cited reasons as colonies being too weak going into winter, winter weather fluctuations, and queen problems.
That combination will sound familiar to anyone who has opened dead-outs in March.
A colony may have enough honey but too few bees to move to it.
A colony may have a queen, but she failed in late summer and did not raise enough winter bees.
A colony may look strong in August but carry high Varroa and virus pressure into the winter-bee production window.
A colony may survive December, then starve in February because the cluster is isolated from stores during a cold period.
A colony may be damp, stressed, and too small to recover.
The important point is that many “winter losses” begin before winter.
Varroa damage is often done before the hive looks weak
Varroa remains one of the central problems because it damages the bees that have to survive winter.
A colony can look respectable in late summer and still be in trouble if mites are high while winter bees are being raised. Those bees may emerge with reduced vitality, virus burden, or shortened lifespan. The hive may still have weight. It may still have bees flying. It may still look alive at the entrance. But biologically, it may already be compromised.
This is why “I treated in fall” is not always enough. The timing matters. If mite pressure is reduced only after winter bees have already been damaged, the beekeeper may see mite drop and assume the problem is solved, while the colony is still entering winter with poor-quality bees.
A better question is:
Were mites controlled early enough to protect the bees that had to live until spring?
That is the management question behind many dead-outs.
Queen problems are not always obvious
Queen failure also gets underestimated because many beekeepers think of queens in simple terms: present or absent.
That is not how colonies work.
A queen can be present and still be the reason the colony is failing. She may be poorly mated, aging, injured, running out of stored sperm, producing too much drone brood, laying a scattered pattern, or simply not producing enough worker bees at the right time.
The OBA survey identified queen problems as one of the top three cited reasons for loss. That should make every beekeeper more serious about late-summer queen evaluation.
A colony with a weak queen in May may disappoint you.
A colony with a weak queen in August may not winter.
By August, the colony is not just producing ordinary summer bees. It is starting to build the population that has to carry it through winter. If the brood nest is poor then, the colony may enter cold weather with too small a cluster or the wrong age structure.
The beekeeper’s job is not just to find the queen. It is to read the brood nest.
Starvation is not always lack of honey
Starvation sounds simple, but in the hive it is often more complicated than “there was no food.”
A colony can starve with honey still present if the cluster is too small, the weather is too cold for movement, food is poorly positioned, or the bees are unable to break cluster and reach stores. This is one reason weak fall colonies are so risky. A large, healthy cluster has more ability to regulate temperature and move through equipment. A small cluster has less range and less resilience.
That means feeding is not just about adding syrup until the hive feels heavy. The beekeeper also has to consider colony size, box configuration, food placement, late-season brood rearing, robbing pressure, and whether the bees have enough time and temperature to properly process feed.
Weather is now a management variable, not background noise
Ontario winters have always been difficult, but unstable weather creates its own problems.
Long cold stretches can restrict cluster movement. Warm spells can increase activity and food consumption. Freeze-thaw cycles can stimulate brood rearing, which raises the colony’s heat and food demands. Wet conditions can worsen moisture problems inside the hive.
The OBA survey specifically named winter weather fluctuations as one of the top three cited reasons for loss. That matters because beekeeping by calendar alone is getting less reliable. Beekeepers have to manage by actual colony condition.
The same date can mean different things in different years. A colony may need feed earlier. A mite treatment may need to be timed differently. A small colony may need to be combined rather than nursed. A strong colony may be fine with a setup that would fail a weak one.
Why this matters economically
Winter loss is not only a biological problem. It is a business problem.
A dead colony means the beekeeper loses the queen, adult bees, brood potential, production time, feed investment, treatment investment, labour, and often part of the next season’s honey crop. Replacement nucs, packages, or queens cost money. Rebuilding takes time. Weak spring colonies may miss early flows. Commercial operators may also lose pollination capacity.
Canadian research modelling commercial beekeeping found that high winter mortality can significantly affect profitability and that operations use strategies such as self-sufficiency and diversification to reduce risk. Even though that study modelled Alberta operations, the principle applies broadly: colony mortality is not just a spring inconvenience. It changes the economics of the entire season.
For Ontario’s small-scale beekeepers, the cost is more personal but still real. A beginner who loses both colonies may need to buy bees again, replace queens, clean up dead-outs, manage old comb, and start the learning curve over with very little continuity.
What the 2025 numbers should change in the bee yard
The practical lesson is not to panic. It is to tighten management.
A beekeeper looking at Ontario’s 2025 numbers should make several changes.
Test mites instead of guessing. Entrance activity tells you almost nothing about mite load. Use a real monitoring method and write the results down.
Protect winter bees before they are raised. Late-summer mite control matters because those bees need to live for months, not weeks.
Evaluate queens by brood pattern and colony trajectory. Seeing the queen is useful. Seeing what she is producing is more useful.
Do not carry weak colonies into winter out of guilt. Combining weak colonies may save more bees than trying to winter several non-viable units separately.
Feed early enough for bees to use it properly. Late emergency feeding is sometimes necessary, but it is not a substitute for timely fall preparation.
Manage moisture as seriously as cold. Bees can handle cold better than cold plus damp.
Keep records by colony. Queen source, mite counts, treatment dates, feed, brood pattern, fall strength, and winter outcome should all be written down.
Learn from dead-outs. A dead colony is not just a loss. It is evidence. Where was the cluster? Was there food? Was the cluster small? Were there mite signs? Was there moisture? What did the queen look like in August? What was the mite count before treatment?
The right conclusion: cautious optimism, not complacency
Ontario’s 2025 winter-loss numbers were better than the year before. That matters. Beekeepers are not powerless, and better management can move the numbers.
But the losses remain high. A 37% commercial winter loss and a 43% small-scale estimate are still serious. The OBA’s 33.5% average winter loss and 39.3% total annual loss show that colonies are being lost both during winter and during the active season.
The encouraging part is that the causes point toward actions beekeepers can actually take. Varroa can be monitored. Queens can be evaluated. Weak colonies can be combined. Food can be managed. Moisture can be reduced. Records can improve decisions. Local experience can sharpen timing.
Ontario beekeeping is still worth doing. But the 2025 numbers make one thing clear: winter survival cannot be treated as a final step after honey harvest. It has to be managed all season.
The colonies that come through winter well are usually not lucky. They are the colonies that went into winter with the right biology: a functioning queen, enough healthy bees, controlled mite pressure, adequate food, and a setup that kept them dry and viable until spring.