That's why my #1 lesson learned from 2016 was pull old comb. Be ruthless. Forget what you've heard about reusing for three years and stop worry about the energy spent on drawing wax. After watching my bees for a couple of years, I could see the ones who'd been given a "jumpstart" with old comb constantly struggling. (BTW, by "old comb" I mean comb that was built during the previous season and contained brood at some point.) The ones that drew fresh comb outperformed "the cheaters" every time.
Finally, I came to the conclusion that I didn't need to keep old comb around because even during a horrible flow, my bees could still fill up their hives and start swarming. It made more sense to let them build fresh, clean comb. By doing so, I could kill two birds with one stone. 1) The bees would have a more healthful environment. 2) Swarming could be delayed (hopefully), or at least better managed.
Well, that was my personal conclusion, but now I've been vindicated! I read an article by Jennifer Berry and Keith Delaplane on the effects of comb age on honey bee colony growth and brood survivorship. Their research, conducted at the University of Georgia, compared colony growth and brood survivorship in hives with old comb vs. hives with new comb over a three-year period. It's a fascinating article, so I highly recommend reading it. However, if you decide not to, here's a summary. Colonies with fresh comb produced a greater area of brood, a greater area of sealed brood, and heavier individual bees. Interestingly, colonies on old comb had a higher survivorship of brood, but as the study pointed out, that really is not a reason to keep old comb around. To quote the authors, "it is possible that the economic savings of using long-lasting comb may be offset by deleterious effects of old comb acting as a biological sink for toxins and pathogens or as a physical constraint on larval development."
Well, that's it in a nutshell, but here are a few more tidbits from the article that I found especially interesting.
On Age of Comb
The article indicated that the combs used in the experiment were of unknown age, but they "were dark and heavy as typical of combs one or more years old." [Bold face is mine.] OK, so maybe some or most of the comb involved in the experiment was really old, but some could have been only a year-old. So I feel like my decision to cull 1-year-old comb isn't so crazy (or wasteful) after all.
On Brood Production
- Old comb harbors numerous toxins and disease-causing contaminants such as nosema and foulbrood, which are spread from colony to colony by infectious wax. The queen may avoid laying in these cells.
- Old comb may also be permeated with brood pheromones that can inhibit egg-laying because the queen perceives the cells to be occupied.
- "Bees prefer to store honey and pollen in cells that have been previously used for brood rear-ing. In the wild, as a colony grows and continues to add new comb, brood rearing gradually shifts into this new comb and the honey is stored in the old brood comb." Actually, I thought this was interesting because all the books say that you should add empty bars between the brood and honey areas to keep the bees by the entrance and honey in the back. I've never found this to work for me. My bees just keep moving the brood further and further toward the back and storing honey in the emptied nest. Now I know why!
- The cells in old comb are smaller than in new comb. As a result, the bees that are produced in old comb don't grow as much as bees in new comb. In fact, "Diminishing space may force larvae to moult to the non-feeding prepupal phase prematurely, causing nurse bees to cap the cells before larvae have developed maximally."
- In this study, bees raised in old comb averaged 8.3% lighter than bees raised on new comb. However, other studies have shown that bees raised on new comb can be up to 19% heavier than those raised on old comb. It may not sound like much, but put it into human terms. Let's say an average woman weighs 140 lbs. A difference of 8.3% - 19% is 11.6 - 26.6 lbs. If a normal, healthy 140-lb woman lost 20 lbs, she'd be pretty unhealthy.
- This is the one area in which old comb sort of outperformed new comb. Because comb absorbs and retains pheromones, the authors hypothesized that nurse bees may have been more stimulated to care for brood in old comb.
- However, this performance was qualified because although brood in old comb was more likely to survive, colonies with new comb produced far more adult bees. This is probably due to the sheer volume of brood produced in colonies with new comb. More eggs are laid and more brood is sealed in colonies with new comb. (See table before.)
- Although more brood survives in colonies with old comb, the number of adults in colonies with old comb was still lower. At least 35 different contaminants in wax have been documented. These contaminants may cause a high mortality rate in adult bees. Additionally, it's possible that returning foragers have a more difficult time locating their colony as contaminants may mask the hive's signature scent.
What do you think? How long do you wait to cull comb? Have you observed any differences in colonies with a preponderance of old or new comb?