>> > AFB scale glows yellow/green in UV light.

>Source of that very interesting fact, please !

I Googled it for you.  Here is one reference:

http://www.ars.usda.gov/is/np/honeybeediseases/honeybeediseases.pdf

--- begin quote ---

...brood combs of diseased colonies usually have a spotty
brood pattern (pepperbox appearance), and the cappings tend to be darker,
concave (sunken), and punctured. The combs may contain the dried
remains of larvae or pupae (called scales), which are found lying length-
wise on the bottom sides of brood cells. Sometimes scales are difficult to
locate because of the condition of the comb. In such cases, scale material
can easily be located using longwave ultraviolet or near-ultraviolet light.
Exposure to wavelengths of 3,100 to 4,000 angstroms causes scale
material to fluoresce. Some discretion must be used with this technique
because honey and pollen may also fluoresce.

--- end quote ---

UV light used to be a bit awkward to use, requiring a lamp and power, but 
with the new LED flashlights being so cheap, everyone can have one in the 
glovebox and one in the toolkit.

AFAIK, the wavelength is not critical, and the common flashlights are between 
380 and 400, but it seems that yellow glasses may improve the detection.

I haven't used UV for thirty years, so I'm hoping someone reading here has 
been experimenting with the new equipment available.

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