# Source of Late Fall Varroa Load



## cryptobrian (Jan 22, 2012)

During a recent presentation by Dr. Eric Mussen, he made a point that high varroa loads that are observed in late fall/early winter often can't be accounted for based on the expanding early fall mite numbers. Indicating that they are coming from elsewhere. He made the point of robbing being one mechanism of transmission. Robbing bees carrying mites are met at the door by guards and the mites subsequently make a dash for the hive. But seemed to really point towards crashing hives with extremely high mite loads being the culprit. That bees in the failing hives head off in search of better conditions and subsequently sneak their way into other hives and bring along with them a lot of mites. 

This was all an aside from the actual topic of the presentation, so it was presented with reference data, and may have been just a conjecture, so I don't want to suggest it was anything more. But I'm curious if anyone is aware of any studies along these lines as it's an interesting hypothesis and to be honest, I wasn't aware that the bees would go off in search of better hives (aside from absconding, but this isn't what he was talking about ... he was talking about individuals moving into existing hive populations).


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## peterloringborst (Jan 19, 2010)

> But I'm curious if anyone is aware of any studies along these lines as it's an interesting hypothesis and to be honest, I wasn't aware that the bees would go off in search of better hives


A few years ago, I heard about the idea that populations spike in August due to infestation from other hives. The idea was that bees preying on weaker hives brought back mites. I found this idea very compelling. Since then I have been applying MAQ treatments in August, which really saves the colonies from mite crash in September or October.

Two summers ago, I did drone brood removal with a vengeance, thinking I was preventing mite buildup. Then the mites went way up in August so I became a believer that these spikes are externally caused. There is evidence in other species of parasites causing the hosts to disperse them, mainly ants. 

But the idea that viruses cause neurological changes is not new, and it is entirely plausible that the sick bees fly off and wind up in the wrong hives. However, I have never seen any hard evidence that these things are actually taking place. I seem to remember a study that discussed late summer mite spikes but I will have to hunt for it.


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## mathesonequip (Jul 9, 2012)

august peaks are part of the mite life cycle. as drone brood slows down so does mite brood. drone brood takes a couple of days longer than workers, the mite in the brood cell lays about an egg a day, the mites prefer drone brood, and drone brood has more mites. the first egg laid by the mite is not fertilized it becomes a male and quickly develops, then the mother mite mates with her son to produce female mites about 1 a day. there are no live male mites left over in the hive.... I got my information from the technical transfer team, Ontario bee assoc.


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## KQ6AR (May 13, 2008)

Mites reproduce more prolifically in drone brood producing at least one more daughter than they do in worker brood. Therefore a lack of drone brood does not explain the increase in mite numbers. It explains why they cause more damage to the hive because of infesting the winter worker bees more heavily.


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## cryptobrian (Jan 22, 2012)

mathesonequip said:


> august peaks are part of the mite life cycle ....


The peak is understood, but that wasn't the point. The point being made was that the numbers at peak can be higher than what would occur through just the expansion of the mites in the hive alone. In other words, you can count the mites in the hive on July 1st, do some maths, and determine that maximum number of mites that could be present on August 1st. This would be based on all of the known parameters of the life cycle, amount of brood, etc., but come August 1st, the number of mites is even greater. Suggesting another (external) source of the mites.


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## canoemaker (Feb 19, 2011)

It seems that if some hives experienced abnormally (or unexpectedly) high mite counts due to external sources--migration of mites, then a corresponding number of hives would experience lower mite counts due to the exodus of those mites. Has anyone seen that born out in mite counts?


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## peterloringborst (Jan 19, 2010)

> It seems that if some hives experienced abnormally (or unexpectedly) high mite counts due to external sources--migration of mites, then a corresponding number of hives would experience lower mite counts due to the exodus of those mites. Has anyone seen that born out in mite counts?


Are you new to beekeeping? Yes, there are hives that experience lower mite counts due to the exodus. Those are the hives that are crashing and dying. After the collapse there are no mites. And no bees.


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## mathesonequip (Jul 9, 2012)

the mites ride around hive to hive on magic bees. yeah right. they multiply at different rates in different hives. the females make more than I cycle. after the brood all hatches they are on the bees waiting to multiply on larvae. nasty little things.


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## peterloringborst (Jan 19, 2010)

I have found quite a few papers referring to reinfestation, but nothing specifically about bees drifting off of dying hives into healthy ones. 



> We quantified the weekly invasion rates and the subsequent mite population growth from the end of July to November 2011 in 28 honey bee colonies kept in two apiaries that had high (HBD) and low (LBD) densities of neighboring colonies.
> 
> We recorded a dangerously high invasion pressure at the HBD site from mid-August through mid-October. This leads to reinvasion of mites in previously treated colonies as is demonstrated by our largely mite-free experimental colonies. One can assume that the invading Varroa mites come from more highly infested colonies of neighboring apiaries. Invasion, coupled with subsequent reproduction by invading mites, can be a substantial problem for beekeepers who treated their colonies earlier, giving them a false sense of security. It also might explain, at least in part, unexpected winter mortality of colonies belonging to experienced beekeepers who have performed Varroa treatments according to recommendations.
> 
> There were large differences between the HBD and LBD sites for infestations of both brood and bees. At the HBD site, the average brood infestation exceeded 6% at the beginning of September. At the end of September, the average infestation rate exceeded 22%, meaning that a quarter of the hatching winter bees were already weakened. At the HBD site, the infestation level of the adult bees was comparatively low until mid-September but then clearly exceeded the autumn economic threshold of 3-5 mites per 100 adult bees suggested for the United States and Canada


Autumn Invasion Rates of Varroa destructor (Mesostigmata: Varroidae) Into Honey Bee (Hymenoptera: Apidae) Colonies and the Resulting Increase in Mite Populations
Author(s): Eva Frey and Peter Rosenkranz
Source: Journal of Economic Entomology, 107(2):508-515. 2014. Published By: Entomological Society of America


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## deknow (Jul 17, 2006)

I'm guessing that the logical conclusion to this is that any bee tree is a threat to beekeepers, and in order to save the bees, the NHB will take the eradication on as a major initiative.


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## peterloringborst (Jan 19, 2010)

It is generally assumed that the reinfestation of colonies with mites is caused by robbing of weak or dying colonies



> There are significant differences between feral colonies and colonies hived at apiaries. In regions with a high density of honey bee colonies the population dynamics are influenced by a permanent exchange of mites when foragers or drones enter foreign colonies or by robbing (Goodwin et al., 2006; Greatti et al., 1992). Through this so called ‘‘reinfestation”, some colonies will lose mites, and others will receive mites. It is interesting to note that the robbing bees will ‘‘receive” the mites from the victim colonies, which often are already weakened through a high Varroa infestation, and that the effective ‘‘robbing distance” is more than 1 km (Renz and Rosenkranz, 2001). This behavior means that during periods with low nectar flow and, therefore, high robbing activities, strong colonies may significantly increase their mite population.


Rosenkranz, P., Aumeier, P., & Ziegelmann, B. (2010). Biology and control of Varroa destructor 
journal of invertebrate pathology, 103, S96-S119.


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## peterloringborst (Jan 19, 2010)

back to the original question: Do bees in the failing hives head off in search of better conditions and subsequently sneak their way into other hives and bring along with them a lot of mites?

I haven't found anything to support this. One would have to mark the bees of a colony and see how many of the bees wound up in other hives. On the other hand, it has been proposed that infested bees deliberately leave colonies to save them, essentially killing themselves to save the parent hive. It has also been proposed that if this self removal becomes to intense, it can have the opposite effect: causing the colony to collapse. Interestingly, in the tropics a colony could lose 90% of its bees and still survive. In our case, losing 90% of the bees in autumn is usually fatal (unless the hives are moved south).



> Altruistic self-removal can only be understood as an
> adaptation at the colony level because isolated colony
> members do not normally survive away from their nest.
> 
> ...


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## dsegrest (May 15, 2014)

It makes more sense that the robber bees would be grabbed by the mites for a ride back to their hive, thus increasing that mite count.

Queens mated before the summer solstice slow their brood production after the solstice. The mites do not slow their brood production so the ratio increases dramatically until the mites just take over. A newly mated queen (after the solstice) and a period with no new brood, can drastically reduce the mite population.


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## BernhardHeuvel (Mar 13, 2013)

In the past I discussed this topic on the phone with Mr. Rosenkranz. There are some flaws in the methods and setup of the experiments so I had and have my doubts. Other scientists in Germany start doubting the concept of "invasion" and "re-invasion" recently. So more research is needed here.

Invasion is a good thing to blame a neighbour. I just didn't find it happen. I have two hives, treatment free, sitting right next to each other on a bench. One of it is filled up with mites, the other has not many mites. This is going for years now. The one hive with the more resistant bees do not have increasing numbers of mites and wasn't negatively affected by the other hive right next to it. After five years, the hive with the high mite load died finally. The other is still alive. (tf)

Another example: there was an apiary of about hundred hives breaking down - a 100 % loss. By varroa. The other apiary - owned by another beekeeper - with about 20 hives on the other side of the road, maybe 100 yards away, has had not a single colony breaking down. If hundred hives break down by varroa and there is no effect on the rest of the hives in that area, invasion can't have that much of effect.

So what is the possible reason for the peak of mites in late summer?! We discussed this with friends and came to the conclusion that it must be triggered inside the colony. Mites can and do change the reproduction rate. For example they can stay longer phoretic on adult bees before they go down into the cells, for two-three weeks. If they decide to invade the cells earlier, the turnover rate and reproduction rate is increased. The triggers why mites change their reproduction rate have been discussed, if you want I will post a translation of the discussion or at least a summary.

Bernhard


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## peterloringborst (Jan 19, 2010)

I think the influx of mites from outside is an established fact. Here is research done more than twenty years ago. They actually counted mites coming into hives that, since they were constantly treated, could not be raising mites internally



> The sources of reinfestation of a treated apiary by Varroa jacobsoni [sic] Oud. were studied in Friuli
> (North-Eastern Italy), in an area with a high density of colonies. Ten colonies, initially Varroa-free,
> were treated with Apistan or Bayvarol strips and mites killed by these treatments were counted twice
> a week for 1 year. Five hives were provided with "drone excluders", to avoid the entrance of drones
> ...


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## Robbin (May 26, 2013)

I didn't think the LOAD increase was from some new source of mites. I thought it came from decreasing numbers of bees. A hive with 5000 mites and 50K bees during the prime build up, fall comes along and the number of bees falls dramatically while the number of mites does not. 5000 mites on 10K bees is a much greater load than 5000 mites on 50K bees. I saw a graph on a mite study somewhere and The number of mites reached a peak along with the number of bees reaching a peak, but the LOAD, number of mites compared to number of bees skyrocketed as the number of mites stayed high while the number of bees plummeted in preparation for wintering. Leading to much greater winter losses.
Sorry, I have no idea where / what study I saw that graph in. But I remember it and take great pains to drive my mite population down in late fall.


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## DPBsbees (Apr 14, 2011)

I believe the same as Robbin. I've heard Randy Oliver explain this quite well, and I belive he has it described well on his site.


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## peterloringborst (Jan 19, 2010)

DPBsbees said:


> I believe the same as Robbin. I've heard Randy Oliver explain this quite well, and I belive he has it described well on his site.


You know, it's not either/or. Both of these contribute to mite buildup. The usual paradigm of internal mite buildup is the main cause, but when the mites have been eradicated and you have buildup anyway you _have to_ look for an external source. The mites in a dying colony have two choices: go down with the ship or find another boat that's floating. 



> *How do Varroa Mites Know when to Leave Honey Bee Hives? It’s all in the Bees’ Wax*
> August 29, 2014 by Entomology Today
> 
> Although they are really tiny, the Varroa mite has the potential to bring large parts of western agriculture to its knees by infesting and destroying honey bee hives. Varroa mites are the “single most detrimental pest of honey bees,” according to the USDA National Honey Bee Health Stakeholder Conference Steering Committee. In addition to attaching to and feeding on the bees, Varroa mites can spread harmful viruses and reduce bee immunity.
> ...


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## BernhardHeuvel (Mar 13, 2013)

peterloringborst said:


> ...when the mites have been eradicated and you have buildup anyway you _have to_ look for an external source.


Yes, when...and if... and so. I know of only one treatment that eradicates 100 % of all mites and that is either fire or sulphur. Problem with that, the bees don't survive it either. With all those experiments and studies not the real incoming mites have been measured, at the entrance, but just the mites that drop inside the hive. One cannot say if those come from inside or from outside the hive. Only thing you can say is: mites continue to drop even if you use hard chemicals over a course of time. When researchers themself say to me: yes, that is a flaw in the study, we shouldn't take things as a fact so quickly. 




peterloringborst said:


> ...PS: It doesn't matter what _you believe._ Try to be open minded, as scientific discoveries are being made all the time.


We should not stop thinking and observing ourselfes and leave it all to "science". Scientists are sceptical for their profession and so we should do, too. 50 % of all studies published are proved wrong later in the future. So we shouldn't take all for granted because it was published. Science is not about finding the truth. Unless you show me a study where the incoming mites are measured at the entrance, I doubt the conclusions drawn by existing invasion studies. 

Everything I experienced so far myself with treatmentfree hives, contradicts the invasion theory.


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## peterloringborst (Jan 19, 2010)

I just received this message from my friend Randy Oliver



> Pete, when I was developing my mite population spreadsheet, one of biggest
> surprises was the profound effect of mite immigration in fall. I used
> numbers from the paper that you cited (as well as others) as variables in
> the model. Keeping bees near sources of mite immigration completely
> ...


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## peterloringborst (Jan 19, 2010)

> Yes, when...and if... and so. I know of only one treatment that eradicates 100 % of all mites and that is either fire or sulphur.


_Nobody said anything about 100%. _If you knock the mites down 90% with treatments, this is sufficient to keep them from building back up and killing the hive, at least for six months or so. The study in question kept miticides in the hives _all the time_ and monitored influx of mites. Try as you might, I don't see how you can dispute that finding.


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## Beetastic (Apr 12, 2011)

I know of a beek in SF who runs lots of rooftop hives. He has had major issues with varroa infestations from collapsing hives. As you know SF, is very "sustainable/treatment free". He'd do tests and treat his hives, only to have them collapse later on from neighbor's bees. It happens.


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## mathesonequip (Jul 9, 2012)

for once WE ARE HAVING A DISCUSSION WHERE SOME REAL KNOWELEDGE FILLED PEOPLE DO NOT FULLY AGREE WITHOUT TOO MUCH OUT SIDE STATIC, from the uniformed, this is great.. uninformed is polite for idiots at times.


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## Robbin (May 26, 2013)

peterloringborst said:


> You know, it's not either/or. Both of these contribute to mite buildup. The usual paradigm of internal mite buildup is the main cause, but when the mites have been eradicated and you have buildup anyway you _have to_ look for an external source. The mites in a dying colony have two choices: go down with the ship or find another boat that's floating.
> 
> 
> 
> PS: It doesn't matter what _you believe._ Try to be open minded, as scientific discoveries are being made all the time.


I don't think the term "believe" implies that the author is either close minded nor has a religious fervor or is unscientific. 
But what I do think is that your arrogance, and your inability to discuss other people’s opinions without belittling them makes you an unacceptable partner in a discussion of anything. I didn’t put you on my ignore list (with the one and only other jerk on beesource that I have on there) when you implied the PHD from UF doing bee studies was stupid and I was even stupider for having quoted him. But this time I’ll plug you into the IGNORE column and I’ll leave you and any threads that you pollute, to your own devices.


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## Beetastic (Apr 12, 2011)

Just adding 2 cents from a friend who is very close contact with Randy Oliver - actually went to him for help after losing colony after colon and has seen 1st hand issues with varroa migration.

....and that's why Beesource turns me off. Well done sir. Well done.


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## crofter (May 5, 2011)

Having a bad day Robbin? Just my thoughts but maybe sometimes a persons public display if disgruntlement is more disruptive of information exchange than the perceived foibles of their target.

I think Peter brings some good meat to the table.


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## Santa Caras (Aug 14, 2013)

mathesonequip said:


> for once WE ARE HAVING A DISCUSSION WHERE SOME REAL KNOWELEDGE FILLED PEOPLE DO NOT FULLY AGREE WITHOUT TOO MUCH OUT SIDE STATIC, from the uniformed, this is great.. uniformed is polite for idiots at times.


Up until this point I was enjoying the conversation between knowledgable people. My Mother did teach me to be quiet and listen. She also taught me manners. Calling other people idiots for a comment is beyond rude.


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## peterloringborst (Jan 19, 2010)

> TOO MUCH OUT SIDE STATIC, from the uniformed, this is great.. uniformed is polite for idiots at times.


I would be more careful what you say about people in uniforms. Some of my best friends wear them.


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## peterloringborst (Jan 19, 2010)

> PS: It doesn't matter what you believe. Try to be open minded, as scientific discoveries are being made all the time.
> 
> I don't think the term "believe" implies that the author is either close minded nor has a religious fervor or is unscientific.


Really, I meant nothing of the sort. Beliefs do tend to be closely held, however, and can be an impediment to learning. We tend to see what we believe, that's all.

However, if I offended anyone by any of my posts, I apologize. Often in the heat of the discussion, we say thoughtless things. Just as often with short exchanges, our messages are misinterpreted. I would much rather continue the discussion and work things out, than to go off in a huff. 

Even so, some things are important, and the issue of reinfestation is one of them. It is very hard for me to be varroa free if Joe down the road has hives crashing and his varroa mites are ending up in my hives. We live in a society and we try to work things out by discussion, and compromise.

At one time all states had bee inspection laws to prevent the spread of bee diseases. In this day and age, it almost seems quaint since all the hives have parasites. But a recent visit to Ontario Canada taught me what a bee community could be like where people respect the knowledge of experts, and try to follow best management practices. Despite this, of course, Ontario lost 50% of the hives over winter, same as NYS. But some things, like bad weather, can't be helped.


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