Someone had written me a letter requesting information about how they might provide homes for swarms of bees of which they were made aware in their area. They weren't interested in becoming beekeepers but they wanted to foster the bees and prevent their destruction.
I wrestled with my response for a while. First, the reason I was wrestling so hard was both the legal and practical sides of this question. The legal varies from state to state but is principally aimed at preventing the harboring and spread of diseases that could cripple our agriculture by leading to the loss of our honeybees. It is illegal in most states to keep bees in hives that do not allow the inspection for disease, specifically American Foul Brood. Thus, honeybees must be kept in "movable frame hives" and not old-fashioned skeps or bee gums.
There is just cause for these laws and precautions. American Foul Brood (AFB) is a spore-forming bacterium. A honeybee larva fed only ten spores of AFB in its first day of life is so severely infected that the bacteria will consume it. When the bacteria have consumed the larva, they go into a spore state where they are protected until the spore is consumed by another larva to repeat the cycle. Each cycle of infection can produce over 2.5 billion spores from a single larva. The larva collapses into a hard scale on the bottom of the cell, protecting the spores from easy, mass removal.
As a hive is weakened by the loss of its replacement bees, it is subject to robbing by stronger colonies of honeybees in the area, thus carrying the spores home to infect their own babies. The spores have been verified to remain viable for over 70 years. (So far the oldest known collection is still viable.) Hot infestation areas are often tracked to old dead-out, abandoned equipment in the back of a garage or barn.
The only method of proven destruction is by burning of the bees, hive, and honey, a major economic loss to the beekeeper without recompense from the government agency forcing the action. Honey containing the spores has no danger to humans but the incidence of AFB is higher in the areas of garbage dumps, presumably because bees find the discarded honey jars containing spores. Commercial processing of honey containing spores does not destroy the spores. We can treat AFB with antibiotics but honey for human use cannot be collected while treatment is ongoing or for thirty days thereafter.
We are also continually fighting the development of resistant strains of the bacterium as the antibiotics are used for many years. AFB strains resistant to the current treatment have been found in the honeys from foreign countries and are now spreading throughout USA and Canada. This resistance is probably the reason so much imported honey has been condemned because it contains antibiotics prohibited from the human food chain in the US but may be the easiest method of protecting the bees in the source countries. This development is another good reason to buy your honey from a trusted local beekeeper.
The practical side includes the problems of dealing with bees, really a wild animal, that can be unpredictable because of individual hive personality and conditions, especially true with African honeybees. The general rule is that bees in a swarm don't sting because they aren't defending a home. But, they can easily be hanging for a few days before someone notices them and they could actually have a home started in a tree because they could not find a suitable enclosed location, thus, they do have a home to defend!
Swarming time is a dangerous period for the bees and only a few of the swarms emerging actually survive to the first winter. They can use a little help to push them along and it takes a little experience to know when and how to aid them. Beekeeping is a challenging hobby or profession. It takes some commitment to learn and a fair investment, ~ $200 to get started with a single hive.
So, now that I have totally discouraged the backyard fruit grower from any attempts at just putting up bee houses in their yard to provide homes from swarming honeybees, what do I recommend to this individual interested in fostering bees in their area? Contact you local beekeeper or beekeepers' club.
I have eight outyards and only one beeyard on my own property. I pay these landowners $25 in honeybee products (honey and candles) each year to allow me to keep my bees there. (Visit my web page to see my beeyard letter and agreement.) Most of these outyards are in suburban backyards where the owners are interested in fruit, gardening, or nature and enjoy having me keep bees there so that they don't have to. In addition, I periodically gather these hives together and move them to pollination. (Last year my bees produced over 200,000 pounds of pumpkins.) I need these nurturing and staging areas to disperse my bees to build up for the job where we overcrowd the bees to ensure that every pumpkin develops to be the best possible, which requires abundant pollen transfer.
As president of the Long Island Beekeepers' Association, I often play matchmaker between two groups of people. One group would like to have a few bees on their property but don't want to become beekeepers. The other group would like to keep bees but their lot (or apartment) is not a suitable location. Sometimes members of the first group have a situation that match my needs and they become one of my outyard landowners. If not, I match them up with a beekeeper in their area.
I also get the swarm calls in our county and pass them on to local beekeepers for collection. Sometimes a swarm call identifies a bee tree with a healthy colony that regularly throws swarms. In this situation, and in all of my outyards, I install swarm bait boxes. Swarm bait boxes are old hive bodies that have rotten corners and such that allow bees egress, and having been used for bees, have the smell of bees. Swarm scouts find these boxes and the swarms move in. Periodic checks of these bait boxes identify occupied boxes and the bees are moved into hives where they can be managed.
So, no, I don't recommend gardeners try to catch and house swarms or put up unmanaged bee houses. Find a local beekeeper and form a partnership, beneficial to both!