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Was Another Field Research Justified?
The Biology Behind Mite Transfer Between Hives
How Much Mite Immigration Really Happens?
How Perform Some Mites Get Transmitted?
How Crucial could be the Drifting of Drones?
How Much Drift can there be of employee Bees?
How significant would be the Guard Bees?
Do Mites and Viruses Cause Increased Drifting?
Robbing vs. “Ordinary” Drifting
How Far Can Mites Hitchike a Ride?
A learn on Bee Drift and Mite Immigration
Part 1
Randy Oliver
ScientificBeekeeping.com
First Posted in ABJ in February 2023
Many beekeepers complain about abrupt late-summer surges inside their varroa matters, blaming all of them on mites immigrating within their hives off their colonies when you look at the area. Whenever my sons and I also suspected this had been occurring in certain our personal yards, I made the decision to perform a field research to learn precisely what had been taking place.
INTRODUCTION
It needs man transportation to maneuver the varroa mite across geographic obstacles, but towards dismay of beekeepers, as soon as introduced into a country, the mite can distribute quickly to any or all colonies in your community. This invasiveness is essentially as a result of all-natural drift of bees, which causes the carrying of mites from hive to hive. We typed by what ended up being understood about mite drift in the springtime of 2018, and claim that if you’re thinking about this topic you very first review my two articles about them [[1]].
SO WAS ANOTHER FIELD STUDY ON MITE DRIFT JUSTIFIED?
To answer that question, let’s take a look at data from Ritter in Germany, taken back in 1987 [[2]]. The report was at German, but really worth translating. Ritter set-up two individual apiaries of 16 mite-free colonies — one out of the foothills associated with the Ebony woodland in a place with reduced colony thickness plus the various other when you look at the Rhine simple with many greatly infested colonies in environmental surroundings, then monitored the infestation prices associated with the bees and brood when you look at the experimental hives in the long run. Their outcomes verified that having heavily-infested colonies when you look at the area make a heckuva huge difference (Figure 1).
Fig. 1. Of interest is the length of time it took for impact showing when you look at the mite washes. At an infestation price of 35per cent, that might be 110 mites in a wash of a half cup bees! part note: in the past the suggestion in Germany would be to utilize fuel for doing mite washes. I suppose which they had been cautious due to their cigarette smokers!
But had been the aforementioned abrupt surge when you look at the infestation price because of a-sudden increase of mites in September? See Figure 2.
Fig. 2. It seems your influence of mite immigration really started initially to occur a long time before September. The obvious “sudden” surge as suggested by mite washes might have really already been because of an exponential escalation in mite introduction in September, into a decreasing amount of adult bees when you look at the hives. This could clarify the reason why also beekeepers that keeping track of via mite washes may nevertheless get amazed!
Practical application: Ritter’s area information truly shows that mite immigration off their colonies when you look at the area can impact the price of mite accumulation in one’s very own hives. And so I desired to plunge much deeper.
In purchase to higher appreciate this trend, we modified my mite design [[3]] to run some simulations (after first confirming that the model could produce results in the ballpark of Ritter’s data). Let’s first take a look at the estimations of details of varroa buildup over time in an untreated colony headed towards collapse in October (Figure 3).
Fig. 3. Allow me to use the simulation above to introduce you to the concept of the “Mite Factory.” I added extra plots for daily amount of mite increase, as well as for the estimated amount of mite exodus on outgoing bees. Read below for explanations.
By the time an untreated, nonresistant Mite Factory about to collapse:
- It will typically contain around 15,000 mites in total.
- The above number will be increasing at a net increase of about 150 mites per day.
- And due to the short lifespan of summer bees, above that number, there will likely be over 150 mites hitching a final ride out of the colony each day [[4]].
unfortuitously, you will find way too many factors for design to anticipate how many those exiting mites fortunate is held to a different hive. Because of the preceding numbers at heart, you might be wondering:
Practical concern: What influence might a Varroa Factory when you look at the area have actually upon my well-managed (addressed) hives?
To response that concern, let’s operate the exact same simulation, but now with several effective remedies (Figure 4).
Fig. 4. Same simulation, but now addressed in April and August, causing a far reduced mite amount in mid-September (around 35). This today provides two baseline figures (15,000 and 35) to try out with.
Now imagine a neighborhood which one from every ten hives is untreated, while another nine colonies are addressed (each containing typically just 35 mites, such as the next simulation). Let’s see just what takes place if an arbitrary 10per cent associated with the 15,000 mites when you look at the untreated colony in some way find a way to uniformly “diffuse” (via bee drift) in to the nine various other managed hives (typically 165 mites per hive)(Figure 5).
Fig. 5. A solitary “Mite Factory” gets the possible to earnestly reinfest the rest of the hives when you look at the area after their particular mid-August therapy (actually, the circulation of mites would obviously be unequal, with colonies getting much more mites than the others). Imagine the end result should your apiary had been in the middle of several “mite factories”!
OK, therefore mite immigration could plainly have a noticeable influence if you currently had your mites really in order, exactly what if perhaps you were operating only a little behind the bend? (Figure 6).
Fig.6. In this simulation of fairly-typical colony administration, the effectiveness associated with the April therapy was just so-so (because of all the mites becoming when you look at the brood). After which the beekeeper hadn’t gotten around to providing an August therapy. Starting September, the simulated colony reveals a mite clean matter of 16 — which may be typical of “average” administration methods [[5]]. But the mite population in that hive would soon exceed 5000, meaning that an immigration of the same 165 mites as in the previous scenario would be only a drop in the bucket!
Practical application: If you’re not staying on top of varroa all season long, it may be a stretch to blame a late-season spike in mite counts upon mite immigration from elsewhere.
It appears as though mite immigration could indeed be an issue for those making the effort to maintain low mite counts. So I felt that a field study to better understand mite immigration in my operation was justified!
BACKGROUND RESEARCH
The first thing I want to do when designing a research project is to find out what is already known. For this article, I’ll snip some quotes (with minor paraphrasing and added emphasis) from relevant publications.
The second thing is then determine the specific questions that I want to try to answer — these will be my study objectives (which I will list below).
THE BIOLOGY BEHIND MITE TRANSFER BETWEEN HIVES
Varroa is a very successful parasite, rapidly reproducing in its own host honey bee colony. But for the parasite’s continued success, bloodlines of the mite must somehow “horizontally transfer” to other host colonies prior to the death of their host colony.
To the mites’ great advantage, they’re able to utilize bees exiting their host colony as an unwitting delivery service that takes them directly into other colonies within flight range. This hitchhiking not only allows varroa to infest newly-established colonies, but also to mix their genes among neighboring host colonies (which helps the mite to evolve).
HOW MUCH MITE IMMIGRATION ACTUALLY OCCURS?
It takes only a single fertile female mite to start an infestation in a colony. But beekeepers soon noticed that the degree of mite immigration was sometimes much more than that. Following Ritter’s publication, in 1988, German researchers Sakofski and Koeniger wrote a chapter called “Natural transfer of Varroa jacobsoni among honeybee colonies in autumn” [[6]]. Plus in 1990 [[7]] they again confirmed that colonies from which varroa had been eliminated by treatment could be reinvaded by the mite, especially during late summer and fall. And then in 1992Greatti [[8]] posted information showing spectacular quantities of mite intrusion occurring in the supervised colonies in Italy. These conclusions had been followed closely by various other analysis, particularly compared to Frey [[9]], who found that mites could drift for a considerable distance. I’ve summarize the above study results previously [[10]], but would they connect with my areas in Ca?
Practical application: There’s without doubt that mite migration between colonies may take spot, and therefore it could be significant. The concerns for beekeepers after that tend to be precisely how and exactly why it takes place, just how much immigration a colony can get, and it is truth be told there whatever we are able to do in order to lower it.
Study Unbiased number 1: to look for the quantity of mite immigration which actually occurs in belated summertime and fall in which we keep my bees.
Study Unbiased number 2: to ascertain whether that mite immigration is regular or episodic.
Study Unbiased # 3: to ascertain whether all hives endure similarly from mite immigration, or whether most are more appealing or receptive than the others.
HOW PERFORM SOME MITES GET TRANSFERRED?
Since the mites rely upon bees to hold all of them with other colonies, it’s vital that you appreciate this aspect. Greatti [[11]] listed the three main methods by which the mite manages to disperse from one colony to another:
- By the drifting of drones, which are known to drift freely between hives.
- By the drifting of worker bees — which will tend to “diffuse” mites from colonies with high infestation to those with low infestation.
- By the robbing of colonies weakened by heavy infestation.
HOW IMPORTANT IS THE DRIFTING OF DRONES?
A recent study by Mortensen [[12]] verified that drones do carry mites. It’s popular that drones have a tendency to move with other hives. Having said that, Greatti, alongside quantifying the specific quantity of mite immigration might occur, tested whether putting drone excluders across entrances of colonies would lower immigration. He unearthed that it failed to.
Practical application: Although drones do countless drifting, they might perhaps not add a great deal to mite drift, and because you will find hardly any drones inside our colonies in belated summertime, used to don’t go after the drone aspect.
HOW FAR DRIFT CAN THERE BE OF EMPLOYEE BEES?
There have now been many scientific studies showing there is significant drift of employee bees, particularly in crowded apiaries, in which over fifty percent the employees in a colony may move at some point inside their resides with other hives [[13]].
But think about the fairly abrupt disappearance associated with the bees from a hive since it collapses through the varroa-virus complex. Do those bees simply “disappear,” or do they end up in various other colonies?
Study Goal # 4: to look for the percentage of employees that drift from collapsing colonies into various other hives.
HOW SIGNIFICANT WILL BE THE GUARD BEES?
There’s another facet of employee drift besides bees simply getting lost — to enter a foreign hive, they very first want to get through the protections. Since I have have traditionally chosen for “gentle” stock, I’ve wondered whether I’ve been unintentionally picking for bloodlines whoever protections might-be much more permissive to drifted bees trying to enter their particular hive (Figure 7).
Fig. 7. Although we breed for gentleness, we usually observe protections performing good work at protecting the entry against intruders.
In 2017 Bordier [[14]] used video cameras to track tagged bees at the entrances of monitored hives (Figure 8).
Fig. 8. I visited the INRA research facility in 2018, and snapped this picture of one of the video entrance monitoring units that they were using.
Bordier concluded that (I’ve boldfaced the highlights):
Drifting behavior is a consequence of orientation errors, and also depends on the acceptance level of the new host colony… changes in drifting intensity are likely the result of an increase in colony acceptance. In normal conditions, only 3.5 % of incoming bees are checked by guard bees, but this permissiveness changes according to season, density of bees and nectar and pollen resources— the acceptance levels of colonies increase when nectar flow is abundant but decrease during dearth periods.
Practical application: So I’m still not clear on the importance of the guards in preventing mite immigration. Of interest is the finding by Cappa [[15]] that guard bees mount a higher protection against drifting bees which were parasitized by a mite (just how much might this play into “mite opposition” of a colony?). Contrast that finding to that particular of Geffre [[16]], who “found that IAPV-inoculated bees were significantly more likely to be accepted by the guards at the colony entrance than were…controls.”
We obviously still have much to learn about guarding and drifting. I set up my study so that we would only recover drifted bees that made it past the guards on the landing board.
DO MITES AND VIRUSES CAUSE INCREASED DRIFTING?
It is well known to biologists that any number of parasites can change the behaviors of their hosts in order to effect better transmission [[17]]. In order recommended by DeGrandi-Hoffman [[18]] in 2017:
We hypothesize that stress from parasitism and virus infection combined with effects that viruses have on cognitive function may contribute to forager drift and mite and virus dispersal.
So is there evidence for increased drift from colonies undergoing collapse? In 1991 Sakofski [[19]] unearthed that:
By comparing amounts of bees drifting from very infested and noninfested little colonies maybe it’s shown that infested colonies drifted more often. The intrusion of mites into bee colonies had been administered during a period of time from springtime to autumn. All colonies revealed reduced values of mite increase which enhanced quite a bit after July and stayed large before start of October. Individual values differed over large ranges that are probably be brought on by burglary.
But in 2000, Neuman [[20]], although finding substantial drift of workers and drones, did not find a correlation between worker bee drift and varroa infestation
Goodwin [[21]] went a field test in brand new Zealand typed in 2006, which six of eight high-mite colonies with marked bees folded and got robbed aside. Despite the fact that:
The typical portion of bees drifting from untreated hives infested with varroa into neighboring addressed hives failed to meet or exceed 3per cent. There had been no considerable differences when considering the portion of drifting bees through the varroa-infested colonies plus the addressed colonies at any phase through the entire test. This shows that the reinfestation of addressed colonies cannot predominantly be a consequence of hefty varroa infestations causing employee bees to move with other colonies, over they often do in almost varroa-free colonies.
And after that in 2014 the idea that highly-infested bees had been predisposed to move was presented with wind by Cervo [[22]]:
At low mite abundance, mites stay within the colony where they are born and promote their reproduction by riding nurses. This preference ensures that mites are quickly transferred to another host larva within the same colony where they can reproduce. When mite abundance increases within the colony, the lack of differences in chemical cues between nurses and foragers probably does not allow mites to discriminate between bees with different tasks and causes mites to ride on both of them…. by riding both nestmate foragers and foreign [robbers], mites increase their probability of leaving the exploited colonies. An infested colony, progressively weakened by parasites and mite-transmitted diseases, finally becomes an easy target for robbing foragers from foreign colonies; these robber foreign bees might represent excellent vectors to directly transfer mites from the old exploited beehive to a new one.
This hypothesis immediately gained traction, and by 2017 the term “Mite Bombs” was being thrown about, although with little supportive evidence. And it was a foggy notion – not clearly differentiating the day-by-day “diffusive” mite drift from high-mite or collapsing colonies, versus the sudden and short-term direct transfer of mites during robbing events that may occur during the collapse of a colony.
In 2017 Bordier [[23]] unearthed that:
Approximately ten percent of your tracked bees drifted into a foreign colony. The drifting prevalence had been impacted by the colony’s area in room although not by N. ceranae parasitism.
There had been no considerable differences when considering the portion of drifting bees through the varroa-infested colonies plus the control colonies at any phase through the entire research. This shows that the reinfestation of addressed colonies cannot predominantly be a consequence of hefty varroa infestations causing employee bees to move with other colonies, over they often do in almost varroa-free colonies….The regular degree of drift in apiaries will, but distribute varroa from untreated to managed colonies.
And in 2019 Peck and Seeley [[24]] unearthed that:
We saw no indications that drifting of bees through the mite donor colonies in to the mite receiver colonies enhanced as mite amounts when you look at the mite donor colonies enhanced.
Practical application: As appealing as a virus-induced escalation in drifting behavior theory is, you will find currently conflicting conclusions (Figure 9).
Fig. 9. It’s an easy task to recognize an unfortunate employee that experienced these types of increased disease price of DWV that its wings couldn’t develop. You could properly believe that every employee within image is contaminated with DWV to some degree, as evidenced because of the dying brood. But does the varroa-DWV complex cause these contaminated bees to move at an increased price?
Study Unbiased # 5: to ascertain whether increased varroa/virus amounts boost bee drift within my procedure.
ROBBING VS. “ORDINARY” DRIFTING
We’ve today worked our way-down to whether mite immigration (a) is mostly as a result of “ordinary” drift of bees from hive to hive (that we call “mite diffusion” considering that the web impact is to go mites from colonies with a high mite focus to people that have reduced focus), or (b) is principally from robbing bees holding mites straight back from varroa-weakened hives. These types of robbing could possibly be surreptitious (and undetected because of the beekeeper) or “overt” (effortlessly seen within entry whenever a collapsing colony gets mobbed by robbers) (Figure 10).
Fig. 10. The strange task within entry, plus the dirt regarding landing board suggests this dwindled colony gets robbed. We think that inside our area, many mite immigration because of robbing might-be through the surreptitious robbing which takes spot during nectar moves, when there will be couple of protections within entry.
Peck and Seeley [[25]] looked into mite drift during robbing events taking place in Ithaca, NY late in the season:
Our data also reveal that the colloquial terminology for [heavily infested] colonies—“mite bombs”—does not accurately describe the mechanisms of intercolony mite transmission that we observed in this study. We saw no sudden “explosion” of mite-carrying bees from sick colonies to each of the healthy colonies via worker drifting. Indeed, we found that few mites passed from the heavily infested (MDC) colonies to the weakly infested (MRC) colonies through either worker drift (mostly to nearby colonies) or drone drift. It was only when the MDCs were weakened so much that they became irresistible robbing targets that mites passed in large numbers from the MDCs to the MRCs.
Practical application: The mites in a colony that is being robbed as it is undergoing collapse (while there are still plenty of live mites in the hive) can certainly hop onto the robbers (which the mites could easily recognize due to their different odor) and get carried back to the robbing colony. But such immediate robbing doesn’t take place in all landscapes — see my ancillary article in this issue.
And finally, Kulhanek published a study last year [[26]].
More bees from reduced mite colonies (n= 37) had been recognized in receiver apiaries than bees from large mite colonies (n= 10). Receiver colony Varroa populace development had been related to visitation by non-natal bees, although not large mite bees alone. Eventually, colonies lacking robbing displays skilled quicker Varroa populace development than screened next-door neighbors. Outcomes suggest going to non-natal bees may vector mites to receiver colonies. These outcomes don’t offer the present two leading ideas with regards to mite immigration – the “mite bomb” principle (bees from large mite colonies emigrating to collapsing colonies), or even the “robbing” principle (natal robbing bees get back house with mites from collapsing colonies).
Practical application: Although mite drift during rob outs can certainly occur, it could be that mite diffusion because of ordinary bee drift are even more essential. Since robbing displays don’t restrict colonies from robbing, Kulhanek’s conclusions claim that they might lower bee (and so, mite) drift (teaser: i shall shortly be posting my personal screening of robbing displays).
Study Unbiased number 6: To determine whether mite immigration correlates with robbing.
There’s nevertheless an additional product of great interest…
HOW FAR may MITES HITCHIKE A RIDE?
A research by Frey last year [[27]] had a surprising finding — that mite drift is not necessarily a function of distance, and that there can be considerable drift even to colonies a mile distant.
During the experimental period, between 85 and 444 mites per colony were introduced into the receiver colonies. There were no significant differences in the invasion rates in relation to the distance between donor and receiver colonies. In total, 2,029 mites were found in the 10 receiver colonies, but these only correspond to 2.5% of the total mite population in the donor colonies at the start of the experiment. This means that the major part of the initial V. destructor population died together with the collapsed host colonies…From a practical perspective we could show that highly infested honey bee colonies present a substantial risk to already treated colonies up to distances of 1.5 km [roughly a mile] away.
Kulhanek [[28]] noticed significant drift between hives in identical lawn, but the woman digital cameras noticed just 47 noticeable bees (away from around 32,000 painted) drifting to receiver hives a half mile or more remote.
Practical application: Frey’s choosing associated with the not enough correlation between mite drift and length had been something which i desired to try in my house lawn.
Study unbiased # 7: to look for the length that bees can move from collapsing colonies.
Study Unbiased #8: to ascertain the way the price of drift to nearby hives even compares to that to hives much more remote.
NEXT MONTH
In another installment I’ll reveal we set-up our area research in order to learn the responses towards detailed targets. Keep tuned in!
ACKNOWLEGEMENTS
Thanks to Peter Borst and Dianne Behnke with regards to their help with finding and checking copies of old analysis documents.
CITATIONS AND NOTES
[1] The Varroa Problem: Bee Drift and Mite Dispersal, areas 16 a & b:
https://scientificbeekeeping.com/the-varroa-problem-part-16a/
https://scientificbeekeeping.com/the-varroa-problem-part-16b/
[2] Ritter, W., & E Leclercq (1987). Entwicklung der Bienen-und Varroa-population in Gebieten mit unterschiedlichen Möglichkeiten der Reinvasion. Tierärzt Umschau 42: 548-51.
[3] https://scientificbeekeeping.com/scibeeimages/Randys-Varroa-Model-V2022-1-1.xlsx
[4] This figure is determined through the calculated amount of non-returning person bees a day (because of the aging process, getting lost, or any other factors), let’s assume that they truly are holding mites of them costing only 2/3 the infestation price associated with the employee bees normally).
[5] Kulhanek K, et al (2021) Survey-derived most readily useful administration methods for garden beekeepers develop colony health insurance and lower death. PLoS ONE 16(1): e0245490.
[6] Sakofski, F & N Koeniger (1988) All-natural transfer of Varroa jacobsoni among honeybee colonies in autumn. In European study on Varroatosis Control.
[7] Sakofski, F, N Koeniger, S Fuchs (1990). Seasonality of honey-bee colony intrusion by Varroa jacobsoniOud. Apidologie, 21(6), 547-550.
[8] Greatti, M, N Milani, F Nazzi (1992). Reinfestation of an acaricide-treated apiary by Varroa jacobsoniOud. Experimental & used acarology, 16(4), 279-286.
[9] Frey, E, H Schnell, P Rosenkranz (2011). Intrusion of Varroa destructor mites into mite-free honey-bee colonies beneath the managed circumstances of a military instruction location. Journal of Apicultural analysis, 50(2), 138-144.
[10] https://scientificbeekeeping.com/the-varroa-problem-part-16b/
[11] Greatti, M (1992) Op. cit.
[12] Mortensen, The, C Jack, J Ellis (2018). The breakthrough of Varroa destructor on drone honey bees, Apis mellifera, at drone congregation places. Parasitology Analysis 117(10): 3337-3339.
[13] Pfeiffer, K & K Crailsheim (1998). Drifting of honeybees. Insectes Sociaux 45(2): 151-167.
[14] Bordier, C, et al (2017) do I need to remain or must I get: honeybee drifting behaviour as a function of parasitism. Apidologie 48(3): 286–297.
[15] Cappa, F, et al (2016) Bee protections identify international foragers with cuticular substance pages changed by phoretic varroa mites. Journal of Apicultural analysis 55(3): 268-277.
[16] Geffre, A, et al (2020). Honey-bee virus triggers context-dependent alterations in number personal behavior. Proceedings associated with the Nationwide Academy of Sciences, 117(19): 10406-10413.
[17] Poulin, roentgen (2010) Parasite manipulation of number behavior. Advances when you look at the Research of Behavior 41: 151-186.
[18] DeGrandi-Hoffman, G, F Ahumada, H Graham (2017). Tend to be dispersal systems switching the host–parasite commitment and enhancing the virulence of Varroa destructor (Mesostigmata: Varroidae) in handled honey-bee (Hymenoptera: Apidae) colonies? Ecological Entomology 46(4): 737-746.
[19] Sakofski, F (1991) Quantitative investigations on transfer of Varroa jacobsoni Oud. In current analysis on bee pathology. Overseas symposium associated with the Overseas Federation of Beekeepers Associations, Gent (Belgium), 5-7 Sep 1990.
[20] Neumann, P, et al (2000) Colony assessment is certainly not suffering from drifting and employee honeybees (Apis mellifera L.) at a performance screening apiary. Apidologie 31: 67–79.
[21] Roentgen M Goodwin, et al (2006) Drift of Varroa destructor-infested employee honey bees to neighbouring colonies. Journal of Apicultural analysis 45(3): 155-156.
[22] Cervo, R, et al (2014) tall Varroa mite variety affects chemical pages of employee bees and mite-host choices. J. Exp. Biol. 217: 2998– 3001.
[23] Bordier, C, (2017) Op. cit.
[24] Peck DT & TD Seeley (2019) Mite bombs or robber lures? The functions of drifting and robbing in Varroa destructortransmission from collapsing honey-bee colonies for their next-door neighbors. PLoS ONE 14(6): e0218392.
[25] Peck DT (2019) op. cit.
[26] Kulhanek, K, et al (2021) Accelerated Varroa destructor populace development in honey-bee (Apis mellifera) colonies is related to visitation from non-natal bees. Scientific reports, 11(1): 1-15.
[27] Frey, E (2011) Op. cit.
[28] Kulhanek, K (2021) op cit.
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