As fall approaches and you start compiling your list of bee equipment you “need” to buy for next year, consider acquiring a double screen board. A double screen board, also known as a Snelgrove board (Leonard Snelgrove invented it in 1934), can be used in multiple ways.
Equipment
A double screen board comes in either an 8 frame or 10 frame box size and is about 1-inch deep with an opening in the center. The center opening is covered with screens on both sides so that bees on one side of the board cannot contact bees on the other side of the board. It often comes with openings in the rim that can be toggled open or closed.
Spring Splits
Often in the spring you want to create a split in order to create a new hive or to prevent swarming. But I have had challenges creating splits in the early spring when the temperature falls and there are not enough bees in the split to keep the brood warm. A double screen board can help to solve this problem. Simply put the new brood box (the split) on top of the other brood box from the original hive with a double screen board between the two brood boxes. The brood box on top of the double screen board will consider itself queenless because queen pheromone cannot be passed bee to bee between the double screen. So the split will create queen cells assuming it has eggs 3 days old or younger and no queen. Or you can insert a new queen in the top brood box and have two hives on top of each other. The advantage of the double screen board is that the split (top brood box) will benefit from the warmth of the brood box below to avoid chilled brood. You should also consider adding a feeder to the top brood box to ensure the bees in the split have sufficient food.
The double screen board has multiple openings along the rim. In the example above, once you insert the double screen board between the two brood boxes, you must open one of the openings in the rim to allow the bees in the top brood box to have an entrance. Some of the forager bees in the top brood box will exit and return to the entrance of the bottom brood box. But this is fine. It is these forager bees that are least accepting of a new queen, so if you are inserting a new queen into the top brood box, your queen acceptance will increase if you have fewer forager bees.
Queen Rearing
Another use for a double screen board is to facilitate creating your own queens. The process may seem a little involved but really it is straightforward once you understand it. The beauty of this process is you can do this without taking a hive out of honey production.
Before I explain the process, let me set the stage for the beginning state of the hive. The hive should consist of two deep brood boxes with zero to several honey supers on top of the brood boxes.
During a honey flow when the bees have plenty of pollen and nectar, you begin the process by reorganizing the frames in the two deep brood boxes. You put frames of larva, eggs, pollen and nurse bees (they will come along for the ride because they will be on the frames of larva and eggs) in brood box #1. It is fine if there is some capped brood in brood box #1. Then put all the other frames and the queen (very important) in brood box #2.
Now we need to reassemble the hive. Put brood box #2 on the hive bottom board followed optionally by a queen excluder and any honey supers. Then add a double screen board and open one of the top entrances in the rim of the double screen board. Then add brood box #1. Finally, you need to feed the top brood box, so depending on your favorite way to feed your bees sugar syrup add a top feeder or frame feeder.
One week later return and look for queen cells on the frames in the top brood box. You can remove each frame with a queen cell and the bees on that frame and put it in a separate NUC with additional frames of honey, pollen, and brood from other hives. My experience has been you usually get about 4 frames with queen cells.
If you want additional queen cells, you can repeat the process of rearranging frames between the top and bottom brood box and wait an additional week. Once you have sufficient queen cells, go through the frames in the top brood box looking very closely for and removing any queen cells, then use a sheet of newspaper to recombine the two brood boxes back to the hive’s original configuration.
Another advantage of this process is that your bottom brood box does not have any larva to feed and take care of, so the bees in the bottom box can focus on collecting nectar and creating more honey!
Additional Resources
American Bee Journal published a very good article in September of 2018 where this process was explained in more detail than what I have provided in this blog. I highly recommend referring to the article below for more details.
Double Screen Boards_JerryBorger_Sept2018
Jim Stellern
Posted 10/10/2020