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Accurately Assessing Brood Viability

Accurately Assessing Brood Viability

One of the ways we look at our bees when we are assessing them to improve our stocks is to look at the brood pattern. But what exactly does it tell us, or does it tell us anything at all? Do we know what to look for when we are looking at the brood? How do you calculate the rate of brood viability of a queen by a casual look at the brood pattern?

I would suggest that it is difficult to make any accurate judgements by this method.

In my view if you have a good queen the brood pattern is invariably good. By a good queen here I mean a queen heading a colony that builds up well in spring. I am not speaking of any other desirable traits that we may wish to develop in our bees.

The fact that a colony builds up well has little to do with the brood pattern as such. What is important is a high percentage of brood viability. The good news is that it is very easy to accurately assess the percentage of brood viability and the test is simple taking no more than a few seconds.

I have been using this method for about fifteen years and all of my records are headed by the percentage of brood viability of the queen.

In order to carry out the test you need a “brood meter.” This is a simple device made from a piece of Perspex and cut in the shape of a rhombus. I have attached a drawing of the one I use but for greater accuracy it can be made larger. The rhombus covers an area of 200 cells on a brood frame.

To use a representative frame of brood is removed from the hive and the bees shaken off. The piece of Perspex is then placed on the brood with the bottom along the bottom of a line of cells and the number of empty cells counted. The result is divided by two and subtracted from 100 to give the percentage.

A “meter” covering 300 or even 400 cells would probably be more accurate but from my experience my 200 meter gives a good result.

It is one of the tests I do on every colony every year. Usually I carry out this test in early April before the bees have built up into too a strong colony. I write the figure in large numbers at the top of the record sheet.

In subsequent inspections if I think that the brood pattern shows more vacant holes than I would expect I will check it again. I have found over the years that a failing queen can be spotted early by this method and appropriate action taken before any damage is done to the colony.

A queen whose brood viability drops during the season is not a suitable queen to breed from or to let the bees supercede from. Requeening from an outside source will solve the problem.

It is not possible to achieve a brood viability of 100%. A percentage of 90% is acceptable and it is probably not possible to achieve better than 94 or 95%.

However when I began looking at brood viability I was surprised at the degree of variability and also how low some of my queens were in this important area.

To make the brood meter you can use the drawing provided or you can get a sheet of foundation and count the number of cells you require. The plan furnished has a design for a 200 meter and a 300 meter.

Once you have the pattern you want the shape can be drawn onto the Perspex. I cut mine on a band saw fitted with a fine blade but my earliest one was cut by hand using a fret saw.

Once you start using this device you will make it part of your first inspection. It’s a bit like using a hive scales – it tells you interesting things that you don’t get to find out otherwise.

Accurately assessing brood viability can become a valuable part of record keeping in the improvement of our bees.

Just in case you think I am very smart to have thought up all this I am not. I heard about it in a throwaway remark by Ron Brown at Gormanston in I think 1987. He showed a piece of perspex and asked what it was used for in one of the infamous quizzes held in those years.

Later I found a picture of the “brood meter” in his book Beekeeping A Seasonal Guide at page 97 and made my own. Since then I have recorded the brood viability regularly and it never crossed my mind that no one else was doing the same.

Jim Ryan North Tipperary BKA