Tropilaelaps Mites, Part 2

Author: Elinor M. Lichtenberg

Size comparison of Varroa (left) and Tropilaelaps(right) mites. (Photo credit I.B. Smith, USDA-ARS)
Size comparison of Varroa (left) and Tropilaelaps (right) mites. (Photo credit I.B. Smith, USDA-ARS)

Varroa mites cause significant harm to honey bee colonies word-wide. A similar pest, Tropilaelaps mites, could cause widespread damage if introduced to Europe or the Americas. We described the natural history of these mites last year. In parts of Asia where both mites are found, the Tropilaelaps mite is often considered a worse pest than the Varroa mite. Its life cycle is much shorter, facilitating rapid population growth.

In Tropilaelaps mites’ native range, beekeepers must treat colonies with acaricides every two weeks to control these mites. US beekeepers currently treat for Varroa mites two or three times per year, too infrequently to control a Tropilaelaps mite invasion. Our best chances of keeping Tropilaelaps mites out of the US rely on 1) enforcing honey bee import restrictions from countries with these mites and 2) catching any invasion early enough that it can be eliminated The US does not allow imports of bees from another nation that has a bee disease, parasite or pest not found in the US. The second strategy relies on disease surveillance systems, such as the USDA-APHIS National Honey Bee Pests and Diseases Survey.

Mite surveys must be both economical to implement and sufficiently sensitive. Sensitivity measures the probability of correctly detecting an infested colony, and is also called the true positive rate. Our new study, published in the Journal of Economic Entomology, compares the efficiency and sensitivity of several different mite detection techniques. We then use our results to determine the number of colonies per apiary, and apiaries per region that should be sampled for Tropilaelaps mites to detect the early stages of an invasion. You can read the abstract here.

Our results found that a fairly new method, the Bump test, is the best compromise between efficiency and sensitivity. This method involves rapping a frame with brood against a metal pan four times to dislodge mites. You can watch it being performed in a video produced by APHIS. Part 1 at 1:12 and 6:03. Part 2 at 0:19. We think this method would make a nice dance move, and encourage you to share your Bump test videos in the comments section. Written and pictorial instructions for performing the Bump test can also be found here.

The Bump test detected 36.3% of infested honey bee colonies in Thai apiaries. This sensitivity level was lower than those of two other tests currently used in Asia: sticky boards inside hives (54.2%) and inspecting worker brood (56.7%). However, the Bump test avoids some of the problems with these other tests. It can be performed quickly, and does not require visiting each apiary twice as use of sticky boards does. Brood destruction is lower than with worker brood inspection, which requires opening 100 cells per colony.

Our data indicate that surveys looking for Tropilaelaps mites should Bump seven colonies per apiary to be 95% confident that sampling detects an infested apiary. The International Office of Epizootics further recommends that screening protocols have a 95% probability of detecting a new parasite that has infested 1% of colonies in the region being screened. To meet this goal, it is necessary to Bump seven colonies in each of 312 apiaries. Under the current National Honey Bee Pests and Diseases Survey, which tests eight colonies per apiary, the number of colonies that must be sampled drops slightly, to 307.

This study provides the data necessary to guide development of the screening protocols necessary to detect and eliminate a Tropilaelaps mite invasion into a new country. We are happy to be able to contribute such data.


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