3) Screened Bottom Boards (SBB)
There seems to much conflicting information on the effectiveness of screen bottom boards. Several studies have looked into whether they suppress mite counts and are effective in controlling mites. Two studies have shown a reduction of 5% in one study, and as much as 17% in the other. Since statistically, the 5% falls within the margin of error or the statically variation of what research uses as a level to declare something a success, screen bottom boards are seen by some as a failure. We see things a bit different when it comes to the benefits of screen bottom boards in our own infield use of this equipment. (Of course one should discount any results of screen bottom board studies, that did not focus on using bees with good hygienic behavior and grooming traits. To use SBB with the best effectiveness, bees able to groom and dislodge mites is a must. And to date, I have not been able to confirm the quality of the bees used in the study.)
From our experience, screen bottom boards allow:
* A means of doing mites counts via the IPM (Integrated Pest Management) board that many now have built into the SBB. This ability to do mite counts is educational and expands the ability to properly manage mites and other issues in the hive.
* Screen bottom boards also add ventilation (moisture control) to the hive. In feral colonies, the natural tree cavity and limited nest volume keep colony size smaller than what most beekeepers strive to achieve in producing honey. Beekeepers manipulate managed hives to reach peak numbers of 50-60,000 bees, while suppressing swarming with expanded cavity size via adding supers, as well as other factors making the colony drastically different than what bees achieve in the wild. Far larger amounts of nectar is collected in managed hives as compared to feral colonies.
* A means of temperature control. The r-value of a cavity in the wild is far different than that of a poorly constructed hive utilizing 1 inch standard pine with an r-value of 1. The much thicker wood of the tree used in a feral colony helps regulate temperature both in the winter and summer. The sun on a hive in the summer makes for additional ventilation a real benefit to the bees in managed hives.
Beekeeping today comes down to an overall management philosophy. There are no magic bees, hives, or single way of keeping bees. If using screen bottom boards lowers the mite levels by 5%, we will be glad to take that 5%, giving the bees the best chances of survival. Combined with genetic selection, other equipment options, and timely management, SBB are a vital piece of equipment.
We once gave a talk called "Building a Silver Bullet, one B-B at a Time". The talk was centered around all the different small items that gave bees a better chance of survival. SBB was one of those items. If your thinking SBB will handle all your mite problems, or think that by using them, all your losses will end, you will be disappointed. But combined with a bunch of other "5%" items, using screen bottom boards can help lower your winter losses.