Cells per square decimeter (dm²) is a useful unit of measure for understanding colony population dynamics and for developing management strategies, but, for practical field diagnostics it is easier to measure the width of a row of 10 cells measured side to side. A dm² is an area 10 cm by 10 cm; cells on both sides of the comb area are counted. To convert cells per dm² to cells per linear dm and then to mm per cell use equation 1:
Equation 1:
cells/dm2 = 2.31 x N² (where N is the number of cells per linear dm)
Example: 850 = 2.31 x (19.18)²
Divide 100 by cells per linear dm to obtain mm per cell
Example: 100 divided 19.2 = 5.2
To convert cells per in² to inches per cell:
Equation 2:
cells/in² = 2.31 x N² (where N = number of cells per inch)
Example: 54.8 = 2.31 x (4.87)²
Equation 3:
cells/dm² = 15.5 x cells/in²
Example: 850 = 15.5 x 54.8
The values in this column represent the width of a single cell as measured between centers of opposing cell walls. The actual cell interior width is one cell wall thickness less than this value.