The case for clean comb: why starting fresh creates healthier, more resilient colonies

 You've probably heard the advice before.

When transferring bees to a new hive, shake the adults onto fresh foundation. Leave the old comb behind.

Most beekeepers resist this. Watching frames of capped brood get set aside feels like throwing away money. Like abandoning baby bees.

The research tells a different story. Starting fresh is often the best thing you can do for your colony's long-term health.

How pesticides accumulate in honeycomb

Honeycomb looks like wax. After a few seasons, it functions more like a filter that's absorbed everything passing through your hive.

Every bee that developed in those cells left something behind—cocoon silk, waste, residue. Every load of nectar and pollen brought traces of whatever your bees encountered in the environment. Every mite treatment you applied bonded partly to the wax.

A 2025 research review published in Insects examined all the studies on old comb. The conclusion: aged combs accumulate pesticides, heavy metals, fungi, bacteria, and pathogens over time. These don't sit there passively. They affect every generation of bees raised in those cells.

Your bees forage across miles of landscape. Agricultural fields, suburban gardens, roadsides—anywhere they find nectar and pollen. They bring back traces of whatever chemicals are out there.

Those traces add up. The landmark Mullin et al. study found an average of 6-7 different pesticides in typical wax samples. Some samples contained nearly 40. The common miticides beekeepers use themselves can stick around in wax for years—one study found residues still detectable two decades after a product was banned.

Heavy metal concentrations climb too. Research on comb aging found that five-year-old comb contains 50-80% more lead, cadmium, and other metals than one-year-old comb from the same location.

Bees raised in contaminated comb don't live as long. Wu et al. found they lose days off their adult lifespan—which matters when a forager's entire working life might only be a week or two.

Queens are especially vulnerable. Even tiny pesticide exposures can cut their fertility significantly.

Why dark brood comb produces smaller bees

Beyond what's in the comb, there's a purely physical issue.

Every bee that develops in a cell leaves a thin layer behind. Cocoon silk. Waste material. Residue the nurse bees can't fully clean out. Generation after generation, these layers build up.

The cells get smaller.

According to the 2025 Insects review, worker cells can shrink by 40% in available space after several years of use. That accumulated material can take up more than 10% of the cell volume.

Researchers have measured this directly. Bees raised in old comb are measurably smaller: shorter bodies, smaller wings, lower birth weight.

Smaller bees have shorter reach when foraging. They produce less wax. They're generally less robust.

The problem compounds. Undersized bees build undersized cells when they construct new comb. The limitations perpetuate themselves across generations.

How comb age affects honey production and colony health

Individual bee problems become colony-level problems.

Studies on comb age and colony performance show that colonies working with old comb have:

1. Less brood. Comparing one-year-old versus four-year-old comb found 35% less sealed brood in the older comb colonies.
2. Shorter worker lifespans. Workers from new-comb colonies lived about 30 days on average. Workers from old-comb colonies lived about 24 days—a 20% reduction in productive life.
3. Lower foraging activity. Colonies with fresh comb had significantly more foragers returning with pollen per minute than colonies using old comb.
4. Reduced honey storage. New-comb colonies stored nearly twice as much honey and pollen as old-comb colonies in direct comparisons.

Brood breaks and varroa mite control

An intentional brood break works as a reset.

When you shake adult bees onto new foundation without transferring brood, you create a period where no new brood is being capped. Varroa mites reproduce inside capped brood cells, so no brood means no mite reproduction for about three weeks. That's roughly one full mite reproductive cycle interrupted—without any chemicals.

Research on brood breaks for Varroa control shows that combining a brood break with treatment increases mite kill rates dramatically. Treatments during broodless periods can achieve 95%+ effectiveness, while the same treatments with brood present often reach only 25-35%.

How long it takes bees to draw new comb

This concern stops most beekeepers from trying fresh starts.

Drawing new comb takes energy. Bees need to consume honey to produce wax—the old rule of thumb is 6-8 pounds of honey to make one pound of wax. Starting from scratch sounds like asking your colony to run a marathon before they can even settle in.

With good thermal efficiency, they build faster than expected.

Beekeepers transferring into Primal Bee hives consistently report that comb-building happens remarkably quickly. Thermal efficiency means bees aren't burning energy just staying warm—they can redirect that energy toward construction.

Feeding accelerates this further. Bees can't fully digest all that sugar, so they excrete the excess as beeswax flakes from tiny slits in their abdomen. The more you feed them, the more wax they produce.

How often to replace brood comb

Beekeeping researchers and extension services have largely converged on the same recommendation: rotate out brood comb every 3-5 years.

The UK National Bee Unit recommends replacement "at least every 3 years," with more frequent rotation after disease or repeated treatments. University of Minnesota's Bee Squad suggests 3-4 year cycles. Australian guidelines recommend 1-3 years for managed hives.

The reasoning is consistent across sources: old comb accumulates problems faster than bees can compensate for them. Regular replacement addresses contamination, cell size reduction, and disease pressure simultaneously.

What to do with old brood frames

You have options.

1. Transfer to another colony. Move the brood frames to strengthen an existing hive in your apiary.
2. Create a nurse colony. Move the old equipment 5-10 feet away. Wait about 15 days until most larvae have emerged as adults, then shake the newborns into your new hive.
3. Assess and abandon. In cases of high contamination risk from Varroa or brood disease, abandon the old frames entirely.
4. For detailed transfer instructions—including how to prepare bees, manage the follower board, and configure feeding—see our complete Transferring from Langstroth guide.

The bottom line

Old comb is a reservoir of pesticides, heavy metals, and pathogens that accumulates with every season. Cells shrink. Bees get smaller. Colony performance drops.

The expert consensus: replace brood comb every 3-5 years.

When you transfer a colony onto fresh foundation, you're giving your bees a clean slate—free from the contamination that's been building up in their old home. The brood break knocks back Varroa. Fresh wax lets bees develop to their full size. A thermally efficient hive means they'll build back faster than expected.