Mite excreta: A new diagnostic tool for detecting Varroa mites!
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. beekeeping industry and is causing significant economic losses. In order to contro 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 carboard grid for counting. During biological investigations of the life history and physiology of this economically important mite, Dr. Eric H. Erickson of our laboratory discovered an indirect method of detecting the mites even when no adults could be located.Although the varroa mites are large enough to be easily seen with the unaided eye, the mites 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 Varroa mites.This visual method involves the characteristic brilliant white fecal spots made on the dark brown brood cells of infested combs. This reliable visual technique will be discussed below along with a presentation photographs showing the appearance of the mite excreta.
In the above photograph 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. Once a frame has been removed, and the bees shaken or brushed off, the inspection for varroa 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.
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.
In this closeup 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 exreta consisted of 95% pure guanine, an important amino acid.
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