The simple answer to the question is no you don't need a queen excluder. In fact, I prefer not to use them most of the time. Why I feel that way is best explained by this video where you can see very clearly that some worker bees are struggling to pass through an excluder.
They may not all be as restrictive as the model in this video, but I believe it illustrates why you will find many references to beekeepers calling it a 'honey excluder'.
But won't I end up with brood in my honey?
Probably not. The queen wants to lay a tight compact brood nest and the bees prefer to store honey above the brood. Even if a prolific queen extends the brood nest into a honey super, the worker bees will likely be eager to fill this space with nectar again once the brood hatches.
It is possible, in some situations, that the bees will create a narrow tower of a brood nest up the middle of many boxes. Circumstances where this is more likely to occur include:
- During a heavy honey flow, if the brood boxes become honey bound, and the queen is desperate for more laying space
- When extra boxes are provided early, the bees may choose to expand upwards rather than fully filling out the width of each box
Dearth's can also complicate things. If the bees are eating more honey then they are bringing in, they will start moving the brood nest upwards as they eat through their stores.
Even though I find some of these situations described above inconvenient at times, I also believe the bees behave this way for a reason, and suspect there can be value in allowing them the freedom to make the choices they feel are optimal in a given situation.
There are some uses for them
Some instances where a queen excluder can come in handy include making splits, raising queens, and locating a particularly elusive queen.
I've seen beekeepers use queen excluders without any problems
I've worked bee yards for years where excluders where used by default. The bees still stored honey in the supers and it did guarantee that the queen stayed below. We found it useful to put the excluders on early to give the bees a chance to get used to them before the supers were really needed. We also always provided an unobstructed path to the honey supers via an upper entrance.