Every time brood is reared in a wax cell, the larva leaves behind a cocoon and fecal residue that the bees cannot fully remove. Over years this builds up as dark, dense comb that shrinks cell volume, produces smaller bees, and — critically — accumulates spores of brood diseases such as American and European foulbrood plus pesticide residues absorbed into the wax. Rotating old comb out on a schedule is one of the simplest, highest-leverage hygiene practices in beekeeping.
Most bee-health guidelines recommend rotating out roughly a third of the brood nest's comb every year, so no frame is older than about three seasons — comb this age already measurably raises spore counts and shrinks worker cell size.
A cutaway hive box holds ten comb frames whose colour and mottled disease-risk overlay darken with simulated age, so you can compare a neglected hive against a well-maintained rotation schedule.
Comb darkens and accumulates pathogen and residue risk the longer it stays in the hive. A staggered rotation schedule keeps the average comb age — and disease risk — low, while no rotation lets both climb unchecked.
Click a frame to select it, then drag its age slider or hit "Replace selected frame" to reset it. Choose a rotation schedule and click "Advance 1 season" repeatedly to watch the hive's average age and risk evolve.
Guidelines from bee-health agencies generally recommend cycling out about a third of brood comb every year, so no frame in active use is older than roughly three seasons.