swarm of honey bees on wood planks

Tropilaelaps mite (pronounced: Tro-pill-lay-laps) is an encroaching bee pest we can no longer ignore in the United States. Tropilaelaps mite distribution is growing globally, but there has yet to be a confirmed report in the U.S. The lack of reports may be explained in two ways. The first and best case is that mites are absent in the U.S., while the second and worst case is that the mites are here but have remained undetected because of the limited Tropilaelaps mite surveillance. 

Countries that border the growing Tropilaelaps mite distribution, such as Australia, are actively testing for Tropilaelaps mites in honey bee colonies. If Tropilaelaps mites escape detection and reach new areas, successful control relies on a rapid response to identify the extent of the invasion. 

This article explains why we must stay vigilant in detecting Tropilaelaps, and how the National Agricultural Genotyping Center (NAGC) is taking a proactive stance on testing for Tropilaelaps mites.  

How Did Tropilaelaps Mites Become a Problem?

The native host for the Tropilaelaps mite is a collection of giant honey bee species, which includes the widespread Apis dorsata, along with two others, Apis laboriosa and Apis breviligula. This group of giant honey bees is found in the southern regions of mainland Asia and island nations. 

While beekeepers still collect honey from wild giant honey bees, the Western or European honey bee— Apis mellifera—dominates apiculture. Compared to other species, Apis mellifera is a clear advantage to beekeepers because it has adapted to life in artificial hives, produces higher honey flows, has lower rates of swarming, is a generalist pollinator, and has lower aggressiveness. 

The widespread introduction of Apis mellifera into Asia increased the opportunities for native and non-native bees to interact and exchange pests. For instance, swarming or escaped colonies of A. mellifera can establish in the wild and directly interact with native bee species during foraging activities. This natural experiment allowed the Tropilaelaps mite to test a new, naïve host, and unfortunately, the jump was successful. There are now two recognized species, Tropilaelaps mercedesae and Tropilaelaps clareae, which have adapted to Apis mellifera.  

Is Tropilaelaps Worse Than Varroa?

A pest that jumps to a new host species is not a new or necessarily rare phenomenon. The new host is usually at a severe disadvantage because they have not yet evolved defense mechanisms against the new threat. With the defenses down, the pest is free to cause considerable damage. 

While not all jumps cause systemic problems, it is clear that the introductions of Varroa and Tropilaelaps mites to Apis mellifera have forced dramatic changes to beekeeping and pest management. Varroa destructor remains the most devastating mite for beekeepers worldwide, resulting in varroois of honey bees from the damage it inflicts, as well as the pathogens it transmits.  

The Tropilaelaps mite has its own set of unique characteristics that experts consider much worse than Varroa destructor. Unlike Varroa, Tropilaelaps mites are true brood parasites and require a constant supply of brood for food. The feeding style of Tropilaelaps inflicts considerable damage to the brood by each mite tearing new feeding wounds during subsequent meals. More wounds provide opportunities for more infections. In contrast, Varroa mites have a communal-like feeding style and multiple mites revisit the same wound. 

Due to the rapid Tropilaelaps life cycle, the mite also has a much higher reproductive rate than Varroa, estimated at 25:1, which quickly overwhelms the brood population. Tropilaelaps mites spend less time outside of capped brood cells and are much smaller than Varroa, near the boundary of human eyesight, making them easy to miss during visual inspection. 

Currently, research on Tropilaelaps mite treatments is growing, but products (acaricide) and methods used for Varroa mites have not been successful, which may be due to the differences in biology and behavior between the mite species.

swarm of honey bees flying toward tree branch

Why More Tropilaelaps Mite Surveillance Is Needed

Protecting U.S. beekeeping from Tropilaelaps and other bee threats depends on our abilities to detect the pest early in its invasion while its population is small and geographically isolated. The extensive transportation routes and dense populations of bees during pollination events (e.g., almonds) provide avenues for rapid spread, while making detection a moving target. Therefore, we must combine resources to build an extensive diagnostic network. 

Conducting surveys is difficult and may require both field and lab diagnostics. Current surveys for Tropilaelaps mites rely on a method called the bump test. The bump test uses microscopes to scan field-collected brood for mites. Traditional approaches using microscopy are typically more time-consuming, lower throughput, and are less sensitive when compared to DNA diagnostics.  

DNA tests, like those offered at NAGC, not only offer quicker and more sensitive diagnostic methods, but also provide a way to test environmental samples for traces of Tropilaelaps.  

We want to avoid or delay history repeating itself. The host jump and spread of Tropilaelaps mites to honey bees echoes the earlier stages of the global varroosis of honey bees. We need to hold off a second mite invasion because U.S. beekeepers are still struggling to maintain colonies and manage Varroa

Observations of Tropilaelaps mites in Apis mellifera on other continents (Africa) and in more temperate, snowy climates in South Korea demonstrate the resilience of these mites and potential for long-distance travel. Now is the time to ramp up testing for Tropilaelaps mites, and the NAGC offers a new test and an opportunity to move towards a large-scale detection survey.  

NAGC’s Role In Tropilaelaps Mite Surveillance

To assist U.S. beekeepers and inspectors, the National Agricultural Genotyping Center (NAGC) has created a new Tropilaelaps test to integrate into its comprehensive panel for bee pests and bee diseases. 

Each year we receive hundreds of samples across the U.S. collected by students, researchers, inspectors, hobbyists, and commercial beekeepers. NAGC is a practical choice as a testing facility for Tropilaelaps surveillance because of these extensive industry connections, the steady flow of bee and environmental samples, and fast turnaround time. 

The new test and sample extraction protocols will detect Tropilaelaps DNA on adult bee, brood, and honey samples. We are also actively working to validate sampling methods for clients to submit hive debris, comb, and other environmental samples. To our knowledge, NAGC is the first diagnostic facility to offer a Tropilaelaps DNA test to the U.S. beekeeping industry. The next step is to put the test to work with the help of apiary inspectors and our beekeeping clients. 

Contact NAGC today to discuss how our testing services can assist you.