The varroa mite, Varroa jacobsoni (Oudemans) is a large reddish mite which is an external parasite on larval forms and adult honey bees. This mite is a serious pest of the U.S. and European beekeeping industry and is causing significant economic losses.

In order to control the mite through cultural or chemical means, early detection of adult mites in apiaries is essential for commercial and hobbyist beekeepers.

Some present methods for detecting the presence of mites and determining levels of infestation involve the use of smoke or other chemicals (e.g. ether) to drive the mites out of the combs. The dead or stunned mites then fall to the bottom of the hive where they collect on a paper sheet or sticky cardboard grid for counting.

During biological investigations of the life history and physiology of this economically important mite, Dr. Eric H. Erickson, of The Carl Hayden Bee Research Center laboratory in Tuscon, discovered an indirect method of detecting the mites even when no adults could be located.

varroa-1Although the mites are large enough to be easily seen with the unaided eye, they are often cryptic and hide from view. Thus this visual appraisal, using the characteristic white mite fecal spots, can provide beekeepers with an easy indicator of the presence of damaging mites. This visual method involves the characteristic brilliant white fecal spots made on the dark brown brood cells of infested combs.

In the photograph above we see a beekeeper with hive tool holding a brood frame and about to start examining the frames for the characteristic white spots that are the mite excreta.

This brood frame has been removed from the hive and is now positioned so that sunlight illuminates the dark brown hexagonal combs. Notice the small white patches scattered at infrequent intervals over the surface.

Notice the small white patches scattered at infrequent intervals over the surface.Once a frame has been removed, and the bees shaken or brushed off, the inspection for mite excreta can begin. The beekeeper should hold the frame with both hands so that it can be easily tilted and closely examined. By placing your back to the sun in morning or afternoon intense sunlight it will be easy to recognize the irregular white spots.

close up of comb showing white excretaIn this close up view we can clearly see several irregular brilliant white patches which are the nitrogenous excreta left by Varroa mites within the open brood cells of the brood nest area.

Interestingly, Drs. Erickson and Allen Cohen (USDA-ARS Western Regional Cotton Laboratory, Phoenix, AZ.) performed sensitive chemical analyses on these mite excreta. Surprisingly, using High Performance Liquid Chromatography, they determined that the mite excreta consisted of 95% pure guanine, an important amino acid.

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