Can Robbing Displays Scale back Mite Immigration?
Section 1
Randy Oliver
ScientificBeekeeping.com
First revealed in ABJ July 2024
After writing about my investigations into bee waft and mite immigration, I used to be requested whether or not the usage of robber guards (aka robbing monitors) may just lower the quantity of mite immigration into hives. So I ran some managed box trials to determine.
Mite Immigration and Bee Go with the flow
To ensure that any parasite to live to tell the tale as a species, it will have to no longer simplest reproduce, but additionally transmit itself or its offspring to contemporary hosts sooner than the unique host dies. No longer simplest that, a a success parasite will have to additionally spatially disperse to new places or host populations.
The varroa mite enjoys vertical transmission from a mom hive to a daughter hive when that colony swarms (for the report, it’s the mum or dad queen and a portion of her colony’s grownup staff that swarm, leaving in the back of what is going to change into a daughter colony if certainly one of her daughter queens effectively friends).
Mites too can have interaction in horizontal transmission when some folks hitch a experience on a flying bee to another colony. Such horizontal transmission additionally leads to spatial dispersal of a mite bloodline to other places than the place it used to be genetically created or the mite used to be born (therefore the speedy unfold of varroa after advent to a space, or the dispersal of miticide-resistant mite genotypes). Those rides happen right through the mite’s dispersal section, which happens between its reproductive section(es), right through which it’s trapped underneath the mobile capping.
Terminology alternate: We initially incorrectly used the time period “phoretic” to explain mites using on grownup bees. However that time period simplest applies to parasite the usage of a brief host only for transportation, with out feeding upon it. We’re now the usage of the extra correct time period “dispersal” section.
All through this dispersal section, mites no longer unusually showcase a choice for using on nurse bees [[1]], since they no longer simplest want to feed upon the well-developed fats our bodies of nurses with the intention to successfully reproduce [[2]], however it’s only nurses that stick their heads into the cells of the Fifth-instar larvae {that a} mite will have to switch to with the intention to reproduce.
I in finding it attention-grabbing that Nolan and Delaplane [[3]] discovered that mites that have no longer but reproduced to showcase a more potent choice for nurse bees over foragers, than those who have already reproduced at least one time. Using on a forager will increase a mite’s chance of demise, however might lead to them catching a experience to every other hive. Apparently that evolution has rewarded this dangerous conduct. As well as, Cervo [[4]] discovered that the variations within the cuticular scent profiles of nurse vs. forager bees disappeared when their colonies suffered from a excessive varroa infestation charge –– which larger the percentage of mites using on staff that go out the hive.
Sensible utility: Because of the above adjustments in cuticle scent and behaviors, colonies affected by a excessive mite infestation charge change into “mite diffusing varroa factories” [[5]], which ends up in the out-of-hive emigration of mites at the foragers, and immigration (by way of drifting) of a few of the ones mites into surrounding colonies (into some colonies greater than others).
Aspect Observe: An Commentary of Attainable Varroa Switch Host?
Varroa destructor quite lately jumped host species when people introduced Apis mellifera into touch with its local host, Apis cerana. Apis mellifera may just now be regarded as as varroa’s most popular host — a minimum of till Ecu honey bees evolve extra resistance to this nasty parasite. Honey bee pupae are the obligate host of varroa –– the one host upon which the mite can reproduce. However the mite additionally makes use of grownup honey bees as switch hosts for dispersal, with the benefit that the mite can have the benefit of with the ability to feed on its experience.
Then again, the mite may just conceivably use a special animal species as a brief switch host, upon which the mite can be known as a phoretic, since that host would serve as only for mechanical switch, moderately than offering any nourishment to the mite.
Varroa (being blind) make a choice their suitable honey bee hosts (whether or not nurse bee, 5th-instar larva, or forager bee) via odor. In an effort to abandon its host honey bee and leap onto a special species for phoretic shipping, a mite would want to in finding that different species to be extra olfactory-attractive.
I can have seen an instance of this very (and up to now unreported) conduct final July, when a bee landed at the arm of my assistant Rose Pasetes (no longer an atypical incidence). I came about to note {that a} varroa mite in an instant deserted that host bee in choice for a human! I whipped out my mobile phone to report this sudden phenomenon (Figures 1 & 2).
Fig. 1 I snapped this picture moments after the mite hopped off the bee and onto Rose’s pores and skin. May we now have been witnessing an strive via a mite to make use of a human as a switch host?
Sensible utility: Paenibacillus larvae, the causative parasite for American Foulbrood illness mechanically passively advantages from people moving their spores to different hives. May varroa receive advantages via actively the usage of us to do the similar?
Fig. 2 The mite (visual at 7:00 under the bee) made no effort to feed upon Rose, but additionally no inclination to go back to the bee. Frightened that we can have been witnessing the evolution of a singular approach of varroa phoretic conduct, we euthanized the mite. We didn’t have a cup sufficiently big to accomplish a mite wash, however Rose later showed that she used to be no longer webhosting any further phoretic mites.
Sensible utility: I used to be in short concerned with a mosquito-breeding laboratory in Brazil, the place there have been a large number of feminine technicians. One of the crucial gals had been obviously mosquito magnets, while others had been unattractive to the bloodsuckers, once more probably because of their specific pores and skin odor. We want to concentrate on decide whether or not varroa is evolving to make the most of beekeepers as hosts for phoretic transmission!
Directly to robbing monitors
OK, possible varroa transmission avoided, let’s transfer onto how it could assist to make use of robbing monitors to lower the immigration of mites into hives. I’ve up to now written broadly at the topics of bee waft and mite immigration [[6]].
Bee conduct: Scouts and foragers do use imaginative and prescient to spot possible floral assets of nectar, however it’s even more uncomplicated for them to easily scout the community for a specific odor that they’ve related to a nectar praise. And that odor could also be emanating from a hive. So far as honey bees are involved, undefended nectar or honey is honest sport. “Robbers” are merely foragers following a floral odor that led them to a hive moderately than to a flower (we will have to consider to not equate a honey bee’s exploitation of a possible meals supply with the morally repugnant plundering of 1 staff of people via every other; a honey bee is incapable of evil intent).
If you happen to put a window display in entrance of a hive front, the resident bees will temporarily discover ways to fly round it, while scout bees from different hives will display up at the display the place the circulate of exhaust air from the hive passes thru it –– investigating the supply of a floral scent emanating from that hive [[7]].
The usage of that idea, robbing monitors use a display to split the trail of a hive’s exhaust circulate of fragrant air from the positioning of the hive front. This makes it tougher for scout bees, following the odor of ripening nectar, to seek out the deliberately offset and diminished front of the safe hive. The hope is that possible robbers will simply surrender looking to get in.
The design of robbing monitors
All robbing monitors that I’ve observed have identical designs (see some examples in Figures 3-5). All too can usually function mouse or shrew guards, and in accordance to a few beekeepers (I’d respect any observations), cut back predation via yellow jackets.
Fig. 3 Nation Rubes sells a “conventional” wood-frame robbing display the usage of low-air-resistance {hardware} fabric for its display (which minimizes any exhaust air being diverted during the front hollow), and a step that separates the display from the adjustable best front hollow. It’s designed for use on backside forums that experience the beeways flush with the hive frame (a at hand beekeeper can regulate any form of front guard to suit their specific hive).
Fig. 4 BeeSmart produces a plastic robbing display with two adjustable best entrances. This design will are compatible between prolonged beeways or on 8-frame hives.
Fig. 5 BeequipNZ sells a chrome steel Robber Guard, which will also be flipped the other way up to supply a full-width opening around the best (the block under the guard on this picture used to be simplest important as a result of I raised the doorway for a stickyboard). Since they had been designed for the narrower New Zealand hive width, I did want to use a wedge at one aspect.
Even though there could also be some congestion when the usage of a small front hollow, even robust colonies tolerate them in sizzling climate in my setting.
The usage of front guards to reduce Mite Immigration right through Overt Robbing
If a colony will get seriously weakened via the varroa/virus advanced whilst there may be any contemporary nectar within, it can be temporarily mobbed and robbed via different colonies. Like rats leaving a sinking send, one of the crucial mites within the collapsing colony might hitchhike rides on invading bees and be taken again to the robbers’ house colony (or colonies) [[8]].
An remark: Remaining 12 months I used to be taking common mite washes from a “mite donor” colony that I used to be nursing, after which one morning watched it get robbed out in a couple of hours. As soon as robbing subsided later within the day, I inspected the colony, now totally emptied of each and every drop of honey. There have been only some useless bees in entrance of the doorway (probably guards that died combating the robbers). At the emptied combs, there used to be a softball-sized cluster of probably younger (and hungry) staff that had it appears no longer engaged in combating. Curious, I washed a part cup of them. The mite wash depend taken two days previous were 44; it had now jumped to 117, which advised that lots of the mites most popular to stay at the younger resident staff, moderately than hitching a experience on a robber.
Sensible utility: Putting in a robbing display as soon as robbing has begun is futile –– the robbers will temporarily determine how you can get in.
Overt vs. Covert Robbing
“Overt robbing” of vulnerable or collapsing colonies is something. However low-level “covert” robbing (aka “surreptitious” or “modern” [[9]] robbing), is when robbers input a hive with out being stopped via the guards, assist themselves to a few saved nectar (or most likely beg it from a returning forager), after which take it again house, later returning for extra. Covert robbing can happen at a low point. Then again, I’ve watched yards of nucleus hives get robbed dry right through a powerful nectar drift via robbers from (probably more potent) colonies somewhere else, without a indicators of combating happening, regardless of dozens of robbers coming into each and every minute.
Anyway, my knowledge recommend that covert robbing might give a contribution to mite “diffusion” from high-mite hives to neighboring colonies. Robbing monitors can cut back both covert or overt robbing from happening. So may just or not it’s of receive advantages to put in robbing monitors by yourself hives?
Sensible utility: A robbing display does no longer save you bees from exiting and reentering their very own guarded hive and robbing different hives. Thus, it will no longer cut back immigration of mites introduced again via its personal robbers.
Then again, putting in robbing monitors on your individual high-mite hives might assist cut back mite diffusion from them on your low-mite hives. However in case you’ve were given varroa below keep an eye on in all of your hives, there can be very little receive advantages to putting in robbing monitors, as opposed to to stay your robust hives from robbing any vulnerable ones.
However what when you have neighboring beekeepers or feral colonies with excessive mite ranges?
Sensible utility: Putting in robbing monitors by yourself hives would no longer save you your colonies from robbing neighboring high-mite hives. You probably have neighboring beekeepers who don’t keep an eye on their mites, you may have the benefit of giving your neighbors robbing monitors for Christmas.
That’s to not say that robbing monitors Couldn’t be of Receive advantages
Even if hanging a robbing display for your hive wouldn’t save you your bees from bringing again mites from different colonies, it’s nonetheless believable that putting in the gadgets may cut back mite immigration from drifting bees. (It would additionally conceivably cut back mite-carrying covert robbers from excessive mite hives from coming into your low-mite hives and leaving their mites in the back of, however it’s no longer transparent how incessantly that in reality takes position).
As detailed in my earlier articles, overdue within the season when mite ranges could also be excessive in neighboring colonies, some hives might revel in considerable mite immigration on days when the elements is favorable for flight (impartial of overt robbing happening). I discovered that a great deal of bee waft (and thus mite dispersal) can happen between high-mite donor hives and bee-attractive receiver hives as much as a part mile away (no longer all hives are nice looking to drifting bees, and a few hives in a backyard don’t revel in any mite immigration).
Sensible utility: I discovered that there generally is a excessive correlation between incoming drifted bees and mite immigration [[10]], with some hives being way more nice looking to drifting bees than others. So mite immigration into a minimum of some of your hives may just plausibly be diminished via the usage of robbing guards –– only if the guards in reality save you drifted bees from coming into.
Checking out whether or not Robbing Guards Scale back Mite Immigration
To decide whether or not putting in front guards would scale back mite immigration, my helpers and I ran 3 other trials in 2022 and 2023, involving over 200 hives in overall, and 8 other apiaries. It wasn’t as simple a query to reply to as I was hoping it could be. Information assortment concerned some 300 mite washes and over one thousand stickyboard counts (taken on moderate two times per week) from mite-zeroed hives [[11]].
Trial A –– Crossover trial, No Mite Donor Hives
On this trial, we tracked mite immigration (by way of stickyboard counts) in 24 hives over 49 days, part with guards on, part with out, swapping the guards from side to side every now and then (crossover design), in order that each and every hive used to be examined with guards on or off (to account for the anticipated huge stage in hive-to-hive variation in mite immigration, based totally upon our earlier analysis).
Trial B –– A couple of Apiary Comparative Trial
Concurrent with Trial A, however in six other yards, we took beginning and finishing mite wash counts from 133 hives, then handled all of them with a low-dose OAE (extended-release oxalic acid) pad to cut back mite buildup. We put in robbing monitors on part of them (randomly blocked via beginning mite depend) to look whether or not having guards on made a distinction of their ultimate infestation charges 51 days later.
Trial C –– Crossover trial, With Mite Donor Hives
On this trial, we tracked mite immigration in 28 hives over 95 days, once more alternating guards being on or off the check hives. However on this trial, we positioned high-mite donor hives adjoining to the check hives to extend the quantity of mite dispersal.
I’m out of house, so will proceed with our findings subsequent month.
Citations and notes
[1] Xie, X, et al (2016) Why do Varroa mites want nurse bees? Medical Reviews 6, 28228
[2] Ramsey, S, et al (2019) Varroa destructor feeds totally on honey bee fats frame tissue and no longer hemolymph. Complaints of the Nationwide Academy of Sciences, 116(5): 1792-1801.
[3] Nolan IV, M & Ok Delaplane (2017) Parasite dispersal chance tolerance is mediated via its reproductive price. Animal Behaviour 132: 247-252.
[4] Cervo, R, et al (2014) Top Varroa mite abundance influences chemical profiles of employee bees and mite–host personal tastes. Magazine of Experimental Biology, 217(17), 2998-3001.
[5] A Find out about on Bee Go with the flow and Mite Immigration: Section 1
[6] A Find out about on Bee Go with the flow and Mite Immigration: Portions 1-6. ABJ February thru July 2023
[7] A Survey on Robbing at Cave in. ABJ February 2023
[8] Peck DT & TD Seeley (2019) Mite bombs or robber lures? The jobs of drifting and robbing in Varroa destructor transmission from collapsing honey bee colonies to their neighbors. PLoS ONE 14(6): e0218392.
[9] Mangum, W (2012) Robbing: Section 2: Modern Robbing. ABJ 152(8): 761-764.
[10] A Find out about on Bee Go with the flow and Mite Immigration Section 5. ABJ June 2023
[11] https://scientificbeekeeping.com/suggested-protocol-to-determine-amount-of-mite-immigration/