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Inside: Right here’s the inside track on Tropilaelaps, the Asian parasitic mite. This tiny creature is a detailed relative of varroa, feeds on growing honey bees, and spreads lethal viruses. However for now, it’s nonetheless restricted to tropical climates exterior of North and South America.
World commerce can carry undesirable items
World commerce has spoiled us. We are able to purchase something from wherever, and earlier than we are able to say Acarapis woodi, the orders plop onto our entrance porches. And if we don’t like what arrives, we are able to ship it again. Worldwide procuring is so easy, we seldom give it some thought.
Sadly, the half about sending it again doesn’t work effectively for invasive species and the pests and pathogens they carry. Many objects we didn’t order arrive beneath our radar, settling in our homelands hooked up to one thing else, hidden from view, or not acknowledged as an issue. Others sneak in regardless of our greatest efforts at monitoring and inspecting. Suppose varroa mites, for instance. A single mistake can have lasting penalties.
This text first appeared in American Bee Journal, Quantity 163 No. 10, October 2023, pp. 1113-1116 .
One creature patiently ready within the emigration queue is Tropilaelaps (tro-pih-lay-laps), additionally referred to as the Asian parasitic mite. As I hearken to scuttlebutt, I sense many beekeepers perceive this creature is keen to pounce, however few know the specifics. They often ask, “How apprehensive ought to we be?” Nicely, that’s a superb query, and one many bee scientists are asking too.
An assortment of unpleasantness
The primary piece of unhealthy information? Tropilaelaps is a detailed relative of the varroa mite. Too shut for consolation, you may say. Like varroa, the Tropilaelaps mite is an ectoparasite, attaching onto or burrowing into the outer floor of its host. As soon as affixed to a young larva or pupa, the mite feeds on the growing bee.
The grownup mites lay eggs inside a honey bee brood cell. When the immature nymphs eclose from their eggs, they feed instantly, weakening the honey bee brood and infecting them with viruses such because the notorious deformed wing virus. In addition they carry black queen cell virus and maybe others. Does that sound acquainted?
A brilliant-fast replica fee
The similarities between varroa and Tropilaelaps are disquieting, however their variations aren’t comforting both. Because the Tropilaelaps mite has a shorter life cycle, it could actually produce offspring at a sooner fee than varroa. Meaning it could actually produce extra mites per bee in a shorter time. As well as, the next proportion of Tropilaelaps females (about 70%) produce not less than one offspring, whereas the speed in varroa is about 50%. Additional including to their wonderful fecundity, mating is non-obligatory. At the least for some people, if they’ll’t discover a mate, they simply reproduce the parthenogenic method.1
As well as, Tropilaelaps are so small, most haven’t the power to latch onto grownup bees. As a substitute, they skip the prolonged “phoretic” interval2 that varroa mites favor (5-7 days when brood is current, 5-6 months with out).3 As a substitute of using round whereas slurping the fats our bodies of grownup bees, they merely get on with extra replica.
As a result of they don’t dally on grownup bees, most Tropilaelaps transfer into a brand new brood cell inside 24 hours of leaving the primary one, shortly infecting as much as 90% of all brood cells in a hive. Some beekeepers who’ve each sorts of mites of their colonies report Tropilaelaps might quickly outnumber varroa 25 to 1.4
How a Tropilaelaps-infected colony dies
A Tropilaelaps-contaminated colony collapses in a lot the identical method as a varroa-infected colony. A beekeeper might discover an total inhabitants drop, an irregular brood sample, perforated cell cappings, uncapped larvae lifeless within the cells, grownup bees with shrunken abdomens, thoraces, or deformed wings, and listless or crawling bees. Many of those signs outcome from the viruses that each varieties of mites carry.
As well as, Tropilaelaps-infected colonies might have many chewed larvae seen within the cells. These die and decay, inflicting a revolting dead-animal odor we don’t affiliate with varroa. This chewed look begins when the mites feed. Not like varroa mites that use the identical puncture wound time and again, Tropilaelaps open a recent wound at each feeding. Tragically, the brood succumbs to being munched alive.
The sheer variety of mites means the employee bees can not sustain with eradicating all of the lifeless our bodies. At first, they might heave lifeless larvae onto the touchdown board, however after some time, the employees hand over and permit the brood rot in place.5
Leaping from one species to a different
Recall that varroa mites had been initially parasites of Apis cerana, the Asian honey bee. As a result of the Asian honey bee and varroa co-evolved over centuries, a stability of energy developed between them. However when beekeepers launched the European honey bee into Asian honey bee territory, the varroa mite crossed over.
Not like Asian honey bees, European honey bees don’t have an in depth protection mechanism towards varroa. As we now know, they lack the genetic wiring to deal with both the parasite or the related viral illnesses in addition to Apis cerana.
Like varroa, Tropilaelaps additionally crossed species when Apis mellifera expanded right into a territory dominated by Apis dorsata and Apis laboriosa. Apis dorsata (the large or rock honey bee) is a local of South and Southeast Asia. The phrase “big” is acceptable as a result of this bee is bigger than most different honey bee species, measuring about 0.7-0.8 inches (17-20 mm) lengthy. The opposite frequent host is Apis laboriosa (the Himalayan big honey bee) which is an astonishing 1.2 inches (3 cm) lengthy.
Though there are 4 species of Tropilaelaps discovered inside these Asian areas, so far as we all know, solely two parasitize Apis mellifera, T. mercedesae, and T. clareae. Of those two, T. mercedesae has a bigger distribution and possibly a higher threat of spreading.
A sizeable drawback
In line with Dr. Samuel Ramsey of the College of Colorado at Boulder, physique dimension is a crucial subject for European honey bees. All else being equal, a large bee can face up to extra parasitism than a peewee bee. In concept, not less than, 5 mites munching on a big larva will do much less harm than 5 mites chewing on a small one.
When varroa moved from A. cerana to A. mellifera, dimension wasn’t a difficulty as a result of each species have roughly the identical dimensions. However the place the distinction is nice, as in A. dorsata vs. A. mellifera, the host’s dimension dictates the quantity of injury a single mite can ship. A big larva might survive an quantity of parasitism that will kill a smaller one.
The way to acknowledge a Tropilaelaps mite
Though each varroa and Tropilaelaps are reddish-brown mites, they’ve radically completely different shapes. Varroa appears to be like extra crablike. The top is on a protracted facet, very like a yummy blue crab. Conversely, Tropilaelaps has a beetle-style physique, with the top at a slim finish.
In case you evaluate the ventral facet of a varroa with the ventral facet of a crab, you possibly can see the eerie similarities. They’re each arthropods, however not in any other case carefully associated. Mites, spiders, and lice are Arachnids (terrestrial creatures), whereas crabs, lobster, and crayfish are crustaceans (aquatic species). Regardless of their many variations, I can’t eat a crab with out envisioning these huge spiders that drape from the timber in my yard. (Then there was the grade faculty science instructor who stated a crab was only a spider gone swimming.)
You could possibly confuse Tropilaelaps with the fly, Braula coeca, though the fly is kind of a bit bigger. Otherwise you may confuse Tropilaelaps with the innocent pollen mite, Mellitiphis alvearius, apart from its rounder form.
Other than a unique physique, Tropilaelaps are tiny in comparison with varroa, maybe a 3rd as giant. From finish to finish, Tropilaelaps prolong about 1 mm, and backward and forward they attain half that far, about 0.5 mm. Examine this to typical varroa mites that measure roughly 1.1 mm lengthy and almost 2 mm large. (Keep in mind, lengthy and brief sides don’t correspond due to their physique shapes.)
In each varroa and Tropilaelaps, the males are smaller than the females. Female and male Tropilaelaps have related physique shapes, however male varroa don’t resemble their females. As a substitute, the males are virtually spherical and measure about 0.7 mm by 0.7 mm.
You’ll be able to see Tropilaelaps after a powdered sugar shake. Simply keep in mind they’re tiny and transfer quick, so it is advisable be fast, too.
Charges of colony failure
Most of us have seen that an untreated colony contaminated with varroa mites collapses in a single to 2 years. The variations in survival instances are possible associated to brood breaks, swarming, or maybe numerous ranges of genetic resistance. However the colony step by step weakens till it lastly folds, typically within the fall or winter.
We’ve realized to acknowledge numerous traits of a varroa-weakened colony. We would discover a lowering bee inhabitants, holes in brood cappings, chewed cappings, and mite feces in brood cells. We might even see an irregular brood sample, deformed wings, shrunken abdomens, or lifeless mites on the underside board. Regardless of the harm, the queen might persist, and you may even see capped brood and honey shops.
With untreated varroa, a yard beekeeper might even get a honey crop earlier than his colony offers up the ghost. However a honey bee colony with Tropilaelaps has a a lot shorter shelf life, extra on the order of a number of months. Left untreated, a colony with Tropilaelaps can be unlikely to provide honey and even make it to the autumn, maybe collapsing throughout its first summer time.
How do beekeepers deal with these mites?
Profitable administration of any organism relies on discovering its weak spot. Essentially the most obtrusive weak spot of Tropilaelaps is its dependence on a continuing provide of bee brood. With out brood, the mites starve as a result of, not like varroa mites, they don’t feed on grownup bees.
Some beekeepers speculate that this single weak spot has slowed Tropilaelaps distribution across the globe, and it might be the explanation we don’t but have them within the Americas. Because the mites can not reside longer than about 36 hours with out bee brood, they’ll’t survive on shipped queens or in bee packages. Except brood is current, Tropilaelaps merely can’t go alongside for the journey.
For now, jurisdictions with Tropilaelaps don’t enable transport or receiving of bees with brood, and shipments of queens and packages are topic to two-day holding intervals to guarantee not one of the mites can survive.
For a similar purpose, common brood breaks are the most effective management for Tropilaelaps. By sequestering the queen lengthy sufficient to guarantee periodic two-day broodless intervals, beekeepers can efficiently handle mite populations. That is just like managing varroa with brood breaks besides the intervals are shorter but extra frequent.
Different management measures that work embody the identical miticides we now use for varroa. These proven to work embody acaricides containing formic acid, thymol, hop beta acids, fluvalinate, and amitraz. As well as, beekeepers in Asia have good outcomes with sublimated sulfur.6
How briskly is Tropilaelaps spreading?
Tropilaelaps favor tropical and semi-tropical environments, resembling exist of their native Southeast Asia. As a result of these areas are heat year-round, the hives produce brood year-round. To this point, the mites haven’t unfold into cooler areas that don’t assist steady bee brood manufacturing.
Though the distribution of Tropilaelaps has elevated within the final fifty years, the growth has not been dramatic. For now, temperatures cool sufficient to halt bee brood manufacturing stop them from spreading. Nonetheless, the thought that retains beekeepers awake at night time is a mite that might survive longer than 36 hours with out bee brood. How a lot farther might they unfold if they may go 48 hours with out brood? Or 60?
To this point, Tropilaelaps have migrated to Kenya, Papua New Guinea, Myanmar, Pakistan, the Philippines, South Korea, Vietnam, and Afghanistan.
It isn’t clear how Tropilaelaps spreads in nature. As a result of solely about 3-4% of grownup mites connect themselves to grownup bees, solely a small proportion transfer between colonies utilizing that technique. Whatever the low fee, nevertheless, robbing or drifting bees might simply transfer these people to different colonies. On a neighborhood scale, beekeepers disperse mites after they make splits or transfer frames between hives.
A possible addition to beekeeper angst
Oddly, I discover beekeepers have a lackadaisical angle towards this new mite. Many argue that we have already got extensively obtainable mite controls, we’ve developed hygienic bees, and we observe administration strategies resembling brood breaks — all issues that may assist management each varroa and Tropilaelaps.
Others consider that as a result of Tropilaelaps can not survive over 36 hours with out honey bee brood, it might be inconceivable to distribute them across the globe. However that’s naïve, like saying one other pandemic couldn’t occur. All it might take is one small mutation to negate that drawback, and one mutation isn’t arduous to think about in a consistently reproducing inhabitants of billions.
One other group of beekeepers argues that we have already got sufficient to fret about, so why hassle? Nicely, that’s the reality. However not contemplating the chance gained’t make Tropilaelaps go away. Pondering is free, and it is a good subject to ponder.
The latest statistics on colony losses are sobering. General, we’re not doing nice with the issues we have already got, so I can’t think about we might add one other mite and never discover. Particularly one which breeds sooner, strikes like lightning, and destroys a higher proportion of colonies than varroa. Certainly, the arrival of Tropilaelaps wouldn’t enhance our colony loss fee even when we put together — not to mention ignore — the chance.
Don’t panic, however keep knowledgeable
Though I agree we shouldn’t panic, I believe we should always take the menace severely sufficient to teach ourselves about it. There’s no purpose to not study the indicators of an infestation, the mite’s life cycle, the way it impacts honey bees, and the management strategies that at the moment are working.
The very fact stays that the Tropilaelaps mite performs nasty with honey bees, so anybody who cares about Apis mellifera ought to study and put together — not less than mentally — for its arrival. If we sweep this mite below the carpet, if we “wait and see” as a result of it’s not right here immediately, we might pay dearly tomorrow.
In an apiary dominated by Tropilaelaps, any beekeeper who’s “just a little late” with mite meds or brood breaks gained’t be capable of squeak by — they breed too quick for that. But when I’m incorrect and Tropilaelaps seems to be “simply one other mite,” then I’ll rejoice. Generally it’s greatest to be incorrect.
Notes and references
- de Guzman LI, Phokasem P, Khongphinitbunjong Ok, Frake AM, & Chantawannakul P. (2018). Profitable replica of unmated Tropilaelaps mercedesae and its implication on mite inhabitants progress in Apis mellifera colonies. Journal of Invertebrate Pathology, 153, 35-37. https://doi.org/10.1016/j.jip.2018.02.010
- Right here, I take advantage of the time period “phoretic” loosely. If the mites are doing extra than simply using, i.e. they’re additionally consuming, phoretic could be the incorrect time period. Nonetheless, the phrase is usually used to explain varroa mites which are using on grownup bees no matter feeding standing, as I’ve used it right here.
- https://bee-health.extension.org/varroa-mite-reproductive-biology/
- https://www.mdbeekeepers.org/product/dr-ramseys-mite-research/
- Ashley N, Mortensen AN, Burleson S, Chelliah G, Johnson Ok, Schmehl DR, and Ellis JD. 2022. Tropilaelaps Mite Tropilaelaps Spp. Delfinado & Baker (Arachnida: Mesostigmata: Laelapidae). College of Florida, IFAS, Entomology and Nematology Division, Featured Creatures, EENY 568.
- Pettis, J. S., Rose, R., & Chaimanee, V. (2016). Chemical and cultural management of Tropilaelaps mercedesae mites in honeybee (Apis mellifera) colonies in Northern Thailand. PLoS ONE, 12(11). https://doi.org/10.1371/journal.pone.0188063
About Me
I backed my love of bee science with a bachelor’s diploma in Agronomic Crops and a grasp’s in Environmental Research. I write extensively about bees, together with a present column in American Bee Journal and previous columns in Two Million Blossoms and Bee Craft. I’ve endured a number of programs in melittology and made in depth identifications of North American bees for iNaturalist and different organizations. My grasp beekeeper certificates issued from U Montana. I’m additionally an English nerd. Extra right here.
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