# 4.2.3.2. Infestation rates of brood

1. Cut out 200 randomly selected capped cells from a brood frame.

Sampling cells from several frames will account for the spatially irregular infestation by varroa.

2. Open each cell and examine it for mite infestation.

Mite infestation can be diagnosed by observation of mites themselves or of their dejection (white rubbery material located most of the times on the two upper walls, towards the bottom of the cell, Fig. 3).

3. Count the total number of cells opened.

4. Count infested cells.

5. Divide the number of infested cells (e.g. 15) by the total number of opened cells (e.g. 212) to obtain the proportion of mite infested cells (0.071).

6. Multiply this figure by 100 to obtain the brood mite infestation rate in mites per 100 cells (7.1).

Depending on the question addressed, more detailed observation of cell infestation can be done (see section 4.3.3. ‘How to measure reproductive success’)