HomeBeekeepingAn On-line Mannequin for Varroa Administration

An On-line Mannequin for Varroa Administration

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An On-line Mannequin for Varroa Administration

Randy Oliver and Trish Harness

First printed in ABJ February 2022


Beekeepers worldwide have been utilizing Randy’s Varroa Mannequin with nice success since its launch in 2017.  However there was a requirement for a web-based model that didn’t require Excel, and could possibly be used on a cellphone.  Trish began engaged on such an app in 2018, and now has it prepared for launch!

No single varroa administration technique is suitable for each beekeeper, since we maintain bees in dissimilar climates, with brief or lengthy brood breaks, numerous colony inhabitants dynamics, numerous remedy home windows of alternative, most popular mite therapies, and disparate objectives and limitations (almond pollination, honey manufacturing, avoidance of comb-contaminating miticides or want to use “natural”strategies, labor prices, and many others.).

For that purpose, with no background in any respect in modeling or spreadsheets, Randy painstakingly labored for over a yr to create his open-source varroa administration mannequin, first publishing it in 2017 [[1]].  The logic for the mannequin is specified by Determine 1.

Fig. 1 The inputs for the mannequin are particulars that may be measured or estimated by the beekeeper:  the mite wash rely, cluster dimension and quantity of brood over the course of the season, the quantity of mite immigration, and the anticipated efficacy of every remedy.

After inputting a couple of values for the above parameters, the mannequin then signifies the anticipated affect of therapies, and permits a beekeeper to customise his or her administration technique (Determine 2).

Fig. 2 A beekeeper can run simulations of varied administration methods with the aim of avoiding the pink crash indicator — it doesn’t price you something to lose a colony on the pc!  On this simulation, a 50% efficacious mite remedy in Could (when excessive efficacy is hard to realize, because of the quantity of mites within the brood), adopted by an 80% efficacious remedy on the primary of October, didn’t do the trick, and the colony can be anticipated to crash.

Notice: Since there are far too many variables concerned for any mannequin to foretell the diploma of colony morbidity as a result of rising virus transmission as a result of mite buildup, or colony efficiency with altering forage or climate, the mannequin assumes that the infestation price is saved to a low sufficient degree to not change the anticipated colony construction.  Thus, the “crash” indicator is simply a tough approximation, and might be adjusted.

Randy inspired, and totally anticipated, bee researchers or skilled modelers to take his crude mannequin and enhance it, however it’s been principally beekeepers themselves who’ve caught errors and provided ideas.  So over time he’s up to date it frequently — the present iteration is Model 19, accessible for obtain at [[2]].

To these acquainted with utilizing Excel spreadsheets, this varroa mannequin is easy to study to make use of, and for these with a deeper understanding of varroa and honey bee biology and copy, is totally customizable for any bee inventory or situations wherever on this planet.

Nevertheless, not each beekeeper has Excel on their pc (and even has a pc), or is comfy with utilizing spreadsheets, so some requested for an easier model that they may obtain to their beloved cellphone.  Not being a programmer himself, Randy put out the phrase for assist…


In 2018, beekeeper/pc science undergrad Trish Harness recruited an upper-level pc science class at Hiram School to collaborate on growing a web-based model of the varroa mannequin.  After the category time period ended, she continued to work diligently on it herself, going by means of numerous iterations over time, bouncing concepts and prototypes backwards and forwards between us.  We’ve lastly arrived at a model that we’re each proud of.  All it’s essential do in your cellphone or laptop computer is to go to chickabuzz.com/mannequin.html and sort in a couple of enter values.  So let’s run a couple of simulations to indicate methods to use it, beginning with Determine 3.

Fig. 3 A screenshot of Trish’s mannequin (on a cellphone, finest considered sideways), utilizing the identical inputs as for Fig. 2 (the blue cells point out the inputted therapies).  She additionally permits the consumer to decide on which parameters they wish to have proven within the chart — on this instance, all are checked.

For Trish’s simplified app, she wished to make the varroa infestation stand out.  So the varroa inhabitants (pink line) is proven at a 10x a number of (topping out at 5000 mites), and the mite wash rely for a pattern of a half cup of bees tops out at 45 (a 14% infestation price).  From a administration standpoint, hitting both of the top-out limits signifies that quick remedy is known as for.

Evaluate the above outcomes for a similar simulation, however as an alternative of solely two therapies, the beekeeper checked the higher gray packing containers to use three moderately-efficacious (80% discount) therapies in April, August and November (Determine 4).

Fig. 4 Success — no crash!  This remedy routine prevented the mite inhabitants or brood infestation price from climbing too excessive, and the colony can be anticipated to outlive the winter.  Notice that this remedy regime can be sustainable, because the beginning and ending mite counts (100 and 104) are basically the identical.

For an additional instance, let’s present a simulation for a beekeeper who bought a nuc in early April, with a beginning varroa inhabitants of solely 50 m ites (Determine 5).

Fig. 5 A beginning wash of a half cup of bees from this nuc would sometimes detect zero mites.  On this simulation, as an alternative of indicating complete brood, it’s clicked to indicate solely the quantity of sealed brood.  The beekeeper utilized a 50% efficacious remedy on the first of August, after which a 90% efficacious remedy on November 1st, because the final of the sealed brood was rising.

If this occurred to be the beekeeper’s first colony, they’d be impressed by their low mite counts in April and December, however the colony should have been affected by a late-season Deformed Wing Virus an infection as a result of its excessive mite degree in October and November, and won’t make it by means of the winter.  And even when it did, it might start the season with 157 mites — 3 times as many because it began with within the earlier yr.  So this varroa administration technique wouldn’t be sustainable.

Within the simulation under (Determine 6), the beekeeper proactively utilized a formic acid remedy in March, after which utilized 5 OAVs each 15 days beginning in mid-August.  The mannequin signifies the anticipated proportion of the mites within the brood at any time (backside row), which lets you estimate the efficacy of varied therapies.  For instance, a 30-second oxalic acid vaporization (OAV), utilizing 1 g per brood chamber could solely kill round 80% of the mites on the grownup bees, and none beneath the cappings.  So for the primary utility, since an estimated 56% of the mites can be within the brood, that would go away 44% out on the bees, for which an 80% kill price would end in an general discount of the mite inhabitants of 35% (44% x 80% = 35%, the determine that the beekeeper would enter).  For every subsequent OAV, the anticipated general efficacy may once more be estimated as proven.

Fig. 6 By proactively hitting the mites in April (and maybe suppressing the swarm impulse by the brood break induced by a formic remedy), the beekeeper received by with a sequence of late-summer low-efficacy OAVs whereas the colony nonetheless contained brood, taking it into the winter with a barely-acceptable infestation price of 8 mites in a wash.  However be aware that the ending mite inhabitants was almost 4 instances that of the beginning, which might spell bother the subsequent season.

Notice: Randy’s been analyzing knowledge units from a number of beekeepers who’ve taken mite drop counts following repeated OAVs.  It seems that repeated functions of 1 g per brood chamber, utilized in a 30-second blast, though “secure” for the colony, could end in comparatively low general efficacy, even when repeated at 4-day intervals, particularly if a lot mite immigration is happening (there was reasonable immigration within the above simulation).  Certainly, mite wash counts may even give the impression of no efficacy (as lately noticed by Berry [[3]]).  Notice that within the above simulation, the mite wash counts (the numbers on the blue line) over the course of 5 OAV functions didn’t change, regardless of lowering the entire mite inhabitants by two-thirds.

For a final simulation, let’s change to a Mediterranean California local weather, with a nectar and pollen move in September and October, and with a bit extra mite immigration throughout late summer season from surrounding neighbors’ hives (Determine 7).

Fig. 7 This San Francisco beekeeper was additionally proactive by treating in mid-March, however received solely 70% mite discount because of the great amount of sealed brood.  By mid-July, there was a lot much less brood because of the summer season dearth, and he or she obtained 90% efficacy with a double utility of Apiguard (thymol).  However then a brand new spike in broodrearing, coupled with troublesome mite immigration, allowed the mites to rebound.  Discover how the proportion of brood cells infested by a minimum of one mite (darkish pink space) constructed up to a degree of no return by late November, inflicting all her bees to “disappear” whereas she was distracted by the vacations.  What a bummer of a option to begin the New Yr!

By operating simulations, one can begin to higher perceive mite inhabitants dynamics, and response to varied therapies.


No mannequin of a posh organic system might be good, however these simulations, based mostly upon Randy’s expertise in his personal operation, in addition to suggestions from different beekeepers worldwide, signifies that they typically hit the mark.  Randy frequently checks the bottom mannequin in opposition to knowledge from others to verify its accuracy.

The complete mannequin requires inputs of solely:

  • A beginning mite infestation price, estimated by working backwards from an precise mite wash rely from a bee pattern taken from a body adjoining to brood at any time level,
  • A alternative of colony sort (or customise on your location by inputting the variety of frames coated with bees and quantity of brood over the course of your season),
  • An estimate of mite immigration (a number of choices given, or customise).
  • And any therapies utilized (the fashions listing anticipated efficacies of varied therapies).

Trish’s mannequin lacks among the customization choices, however can be utilized proper within the area in your cellphone.

There’s no purpose to be shocked by mites unexpectedly getting uncontrolled in your hives.  By operating simulations, you may check out numerous mite administration methods on your colonies prematurely, adjusting them on your accessible remedy home windows, working round honey flows, and rotating completely different therapies to keep away from breeding resistant mites.

Sensible utility:  We’ve discovered that probably the most profitable technique is to cope with varroa proactivelysomewhat than reactively.  Get forward of the mites as early within the spring as potential, so that you simply go into the honey move with a particularly low infestation price, then harvest your honey as quickly as you may after the move, and knock the mites again earlier than your colonies are producing their final rounds of brood earlier than winter.


Trish has labored long and hard to create this cellular model of my varroa mannequin, and plans to proceed to enhance and replace it (at all times verify for the most recent model).  She doesn’t receives a commission for this, so in the event you discover it to be helpful, please ship her a donation.  Her web site is Chickabuzz.com [[4]] and her on-line mannequin might be accessed at chickabuzz.com/mannequin.html


[1] https://scientificbeekeeping.com/the-varroa-problem-part-12/

[2] https://scientificbeekeeping.com/randys-varroa-model/

[3] Berry, Jennifer (2021) A number of functions of vaporized oxalic acid.  Bee Tradition Dec. 2021: 70-73.

[4] Trish’s web site: https://chickabuzz.com/



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