How to Test ACF at Home

Updated: Jun 25

"I am applying ACF on thousands of acres. I bought a microscope and tried to see the bugs, but I'm not sure what I'm looking at!"


We get this a lot. Although your microscope from Canadian Tire might not cut it, there are certain things you can do to evaluate a sample ACF-SR at home.


First, let's start with some information on the different types of microscopes:

With the range of microscopes noted above, only the compound microscope has some use in viewing bacteria, along with a practical price.


It is important to note that bacteria range in size from 1 to 10 microns (a millionth of a metre). Since the upper limit of magnification is 1000 times, there are many problems in attempting to identify bacteria with a compound microscope:


1. Bacteria are small (1 to 10 microns): In order to see their shape, it is necessary to use a magnification of about 400x to 1000x. The optics must be good in order to resolve them properly at this magnification.


2. Difficult to focus: At a high magnification, the bacterial cells will float in and out of focus, especially if the layer of water between the cover glass and the slide is too thick.


3. Bacteria are transparent: Bacteria will show their colour only if they are present in a colony. Individual cells present on the slide are clear. Regular, bright-field optics will only show the bacteria if one closes the condenser iris diaphragm. This is due to the difference in the refractive index between the water and the bacterial cells.


4. Bacteria are difficult to recognize: An untrained eye may have problems differentiating bacteria from small dust and dirt on the slide. Some bacteria also form clumps a