A Learn about on Bee Flow and Mite Immigration
Section 6
Randy Oliver
ScientificBeekeeping.com
First revealed in ABJ July 2023
In our 2018 learn about within the California foothills, we showed that bees certainly flow from collapsing colonies to different hives, even to these at really extensive distance. And that drifting may end up in quite a lot of mite immigration into the ones hives. However there’s strangely little laborious information on how a lot mite immigration takes position in different settings.
It’s simple for beekeepers responsible rapidly-increasing mite wash counts in overdue summer time or autumn on immigration of varroa because of drifting or robbing. However rather then with regards to the robbing of a high-mite colony (which might lead to mites catching a trip again on a robber), the traditional hive-to-hive drifting of bees could be anticipated to have an total impact of averaging the infestation ranges of all colonies inside of flight vary, moderately than concentrating mites into most effective the well-managed hives. Despite the fact that some colonies seem to be extra sexy to drifting bees than others, the whole ensuing mite flow would most probably mirror the method of diffusion ― “the web motion of anything else most often from a area of upper focus to a area of decrease focus.”
The information from my house apiary that I confirmed in Section 4 of this sequence indicated a median immigration of most effective 245 mites in line with hive over a two-month duration, regardless of having 9 colonies collapsing from varroa in the similar backyard).
Sensible software: That quantity of immigration would slightly be noticeable in a mite wash, since in a colony of 40,000 grownup bees, assuming that part the immigrated mites wound up within the brood, the ones 245 mites, despite the fact that that they had immigrated all of sudden, would have most effective larger the collection of mites in a pattern of a part cup of bees via a rely of one. Such a lot for a “mite bombing” having taken position.
So despite the fact that I’m suspecting that my sons and I will be able to’t blame our August varroa spikes on bee flow, may just or not it’s believable in other places? One thing that in reality surprises me is the paucity of research to quantify the true quantity of mite immigration usually happening in several areas of the U.S. So in 2019 I put out a choice for Citizen Science volunteers to gather mite immigration counts. I used to be disillusioned that strangely few beekeepers answered. However those that did equipped us with some precious laborious information ― thanks!
THE PROJECT
I equipped the volunteers a protocol to apply [[1]], and my helper Brooke and I despatched them programs of miticide strips and directions, together with pattern information sheets. As is standard with beekeepers unaccustomed to the quantity of labor concerned within the putting in place a box trial and accumulating information, just a few have been in a position to finish the important preparation and paintings. However I did obtain just right information from a spread of localities.
VALIDATING THE METHODOLOGY
To be able to quantify mite immigration, the protocol for this learn about concerned proactively getting rid of the reproducing varroa inhabitants from the hives — beginning no less than six weeks prior to information assortment. That is achieved via concurrently treating with Apivar and Apistan strips, that have two other modes of motion (I’m lately additionally including OAE sponges), and possibly brood elimination. As I identified in Section 4 of this sequence, one will have to then validate that the colonies to be monitored are in fact freed from mites. Such validation isn’t essentially as simply showed as you may suppose!
The perfect and absolute best solution to ascertain {that a} colony is freed from mites is to watch the sticky forums, however on days by which bees are flying, you’ll be able to’t inform whether or not the dropped mites got here from out of doors or inside the hive. So for affirmation you want to test mite drop counts on wet or chilly days which forestall bee flight, thus getting rid of the danger for mite immigration by means of drifting or robbing bees (as proven in Determine 8 in Section 4). However the place I reside, it doesn’t generally rain or get chilly within the August-October time frame all the way through which we’re focused on mite immigration.
Some other validation is that the mite counts drop to 0 in November, which might without a doubt recommend that the hive is freed from mites at the moment, however doesn’t essentially imply that the colony began freed from mites at first of information assortment (because the extended-release miticides would possibly motive a residual breeding inhabitants of mites within the colony at the beginning of tracking to dwindle over the years).
It befell to me as I used to be writing this text that I must examine our mite drop counts to these of untreated Regulate hives in the similar backyard. Missing the ones, I spent a few hours looking the web for standard mite drop curves over the process a season — I used to be shocked at how little information is in fact revealed! (Please let me know if of any just right information units of herbal mite falls in untreated hives over the process a season).
One may just carry out sealed brood dissection, however this is tedious, and takes some apply, just right lights, and magnification.
So why no longer easy affirmation via a mite wash of a part cup of bees? To my wonder, a handled colony would possibly show off mite wash counts of 0, however nonetheless be it sounds as if generating considerable amounts of mites by itself (I’ll display an instance subsequent month). I highlighted “it sounds as if” since out of a bunch of handled hives in the similar apiary, one would possibly proceed to show off a ways upper day by day (and constant) mite drop counts than the remaining — regardless of appearing mite wash counts of 0 daily ― strongly suggesting that the colony is generating its personal mites. Something that I’ve spotted is that the site of the dropped mites at the sticky board is also a very powerful clue (Figures 1 & 2).
Fig. 1 On this picture of a sticky board, I positioned items of grass stem pointing to every mite at the board. What we apply is that during a mite-free colony, mites that experience are available by means of immigration (and are then quickly killed via the miticides) have a tendency to fall out of doors of the realm without delay underneath the broodnest, which is indicated via the rows of uncapping particles that fell between the brood frames.
Fig. 2 Alternatively, on this sticky board the fallen mites are all without delay underneath the brood space, main me to suspect that mite replica was once happening within the hive.
I’m a great deal appreciative of the efforts installed via the volunteers concerned with this learn about, and lots of the information despatched to me indicated that the monitored hives have been certainly mite loose (or just about so). I censored the few mite rely information that instructed {that a} colony was once generating its personal mites.
THE RESULTS
Let’s first check out the mite counts via Dr. Cahit Ozturk from the recent, dry, and sparse panorama of the Arizona State College Bee Lab (Determine 3).
Fig. 3 Very similar to my observations, there was once huge colony-to-colony variation in mite drops in Dr. Ozturk’s hives, in addition to other curves for drop depth. I checked the elements historical past for the time frame, which indicated that temperatures have been lots heat for bee flight in November and December, however there was once no precipitation. The common cumulative drop in line with hive was once 151 mites — no longer so much, however just about steady.
I requested Dr. Ozturk in regards to the most probably resources of the drifted mites; the college maintains round 100 Ecu (and a few captured feral) colonies below misted color constructions close by. Now let’s transfer from dry Arizona to the wet coast of Maryland (Determine 4).
Fig. 4 Debbie Hewitt’s drop counts in wet, inexperienced coastal Maryland recommend that her hives have been certainly mite-free previous to late-season immigration. One hive obviously took in additional mites, so I broke down the cumulative rely curves. Hive #1 were given hammered with 1050 mites; Hive #2 with a little bit over 500.
Sensible software: On this case, Debbie may just certainly say that her Hive #1 were given mite bombed. A colony can most often tolerate a complete mite inhabitants of 1000 going into wintry weather. In Debbie’s location, apparently that despite the fact that her varroa control program comes to a pre-winter remedy in early October, {that a} colony may just get reinfested by means of mite immigration to a harmful degree via the tip of November. It is a best possible representation of why ― as soon as a colony is going broodless — the applying of an early-winter remedy may also be so vital.
And now let’s transfer as much as New York (Determine 5).
Fig. 5 Elwin Stillman monitored a unmarried hive, beginning with mite drop counts of 0 till the tip of June (nice prep Elwin!). His mite immigration curve peaked previous than did Debbie’s, as we’d be expecting from his upper latitude. Despite the fact that his hive obviously took in mites, it was once no longer sufficient to make a large distinction for varroa control.
There was once any other volunteer round the corner in New York (Determine 6).
Fig. 6 Kyle Mulligan’s hives weren’t a ways from Elwin’s, and his counts additionally seem to mirror most effective immigration. Despite the fact that the counts for the 2 hives didn’t height on the similar time, they each gained just about the similar cumulative totals coming near 500 — possibly no longer sufficient to mention that they have been “bombed,” however obviously sufficient to suggest that he must come with a “clean-up” remedy going into wintry weather.
Let’s now go back to California (Figures 7 & 8).
Fig. 7 I’ve visited Hal Liske’s well-managed apiary at his glorious El Sol vineyard, and wouldn’t be expecting there to be a lot mite flow power.
Fig. 8 Hal’s 3 monitored hives exhibited remarkably equivalent mite counts, and as anticipated, no longer a lot mite immigration.
Farther south of Hal is my longtime supporter Madeleine Mead (thank you Madeleine!), whose apiary is in a sizzling, arid, and sparse panorama with most probably few surrounding colonies (Determine 9).
Fig. 9 Only a few mites stuck rides into Madeleine’s hives (loss of a colour column signifies a nil rely). I used to be curious in regards to the close to cessation of mite immigration in overdue September, so checked her climate historical past. The day by day excessive dropped from 100°F to simply 70, however there was once no rain or wind, so I will be able to’t provide an explanation for. Mite immigration went again up all the way through her heat October and immigration tapered off as the elements in the end cooled on the finish of November.
Sensible software: A normal colony would possibly to migrate way more mites on a daily basis by itself exiting staff who don’t go back, than it receives from bees drifting in from different colonies.. Let’s do the maths: From a colony in September, there are about 1000 bees an afternoon flying off to die of previous age. At a low mite infestation charge of even 1%, that will be 10 mites in line with day being flown out of the hive by no means to go back. On most effective someday did any of Madeleine’s hives succeed in 10 incoming mites. That small quantity of mite immigration would no longer be anticipated to tip the steadiness to any nice extent.
DISCUSSION
Thanks volunteers ― the information that you just gathered was once very informative!
The volume of mite immigration into the monitored hives in rural spaces of the West was once rarely sufficient to enhance the mite bomb speculation.
Alternatively, Debbie and Kyle’s apiaries at the East Coast, in spaces by which I’d be expecting a large number of beekeepers and possibly an abundance of feral colonies, no longer strangely exhibited a ways upper quantities of mite immigration, and so they may just legitimately say that they were given bombed via mites (despite the fact that it’s no longer transparent as as to if any unmarried colony was once the bomb). Despite the fact that I haven’t observed laborious information, beekeepers in different city spaces the place there are a number of beekeepers who don’t do a just right activity of managing varroa, inform me that mite immigration is a big factor for them overdue within the season.
Sensible software: What with the entire communicate and blame amongst beekeepers about mite immigration into their hives, shall we positive use extra laborious information similar to that above for each and every area within the nation. Let me know if you wish to gather some!
Subsequent month I’ll display the result of two experiments that we ran remaining 12 months to check the impact of front guards on decreasing mite immigration.
ACKNOWLEDGEMENTS
My nice appreciation to my helper Brooke Molina, and volunteers Cahit Ozturk, Elwin Stillman, Hal Liske, Kyle Mulligan, Debbie Hewitt, Madeleine Mead, and Dave Munkvold.
CITATIONS AND NOTES
[1] https://scientificbeekeeping.com/mite-drift-quantification/