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An On-line Mannequin for Varroa Administration

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An On-line Mannequin for Varroa Administration

Randy Oliver and Trish Harness

First revealed 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 an internet model that didn’t require Excel, and might be used on a mobile phone.  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, various colony inhabitants dynamics, varied remedy home windows of alternative, most popular mite therapies, and disparate targets and limitations (almond pollination, honey manufacturing, avoidance of comb-contaminating miticides or want to use “natural”strategies, labor prices, and so forth.).

For that purpose, with no background in any way 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 number of values for the above parameters, the mannequin then signifies the anticipated influence 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 purpose of avoiding the crimson 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.

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

Randy inspired, and absolutely anticipated, bee researchers or skilled modelers to take his crude mannequin and enhance it, but it surely’s been largely beekeepers themselves who’ve caught errors and provided options.  So through the years he’s up to date it frequently — the present iteration is Model 19, out there for obtain at [[2]].

To these accustomed to utilizing Excel spreadsheets, this varroa mannequin is easy to be taught to make use of, and for these with a deeper understanding of varroa and honey bee biology and replica, is absolutely customizable for any bee inventory or situations wherever on the earth.

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


In 2018, beekeeper/laptop science undergrad Trish Harness recruited an upper-level laptop science class at Hiram Faculty to collaborate on creating an internet model of the varroa mannequin.  After the category time period ended, she continued to work diligently on it herself, going via numerous iterations through the years, bouncing concepts and prototypes backwards and forwards between us.  We’ve lastly arrived at a model that we’re each pleased with.  All you might want to do in your mobile phone or laptop computer is to go to and kind in a number of enter values.  So let’s run a number of simulations to indicate methods to use it, beginning with Determine 3.

Fig. 3 A screenshot of Trish’s mannequin (on a mobile phone, greatest considered sideways), utilizing the identical inputs as for Fig. 2 (the blue cells point out the inputted therapies).  She additionally permits the person 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 (crimson 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 fast remedy known as for.

Examine the above outcomes for a similar simulation, however as an alternative of solely two therapies, the beekeeper checked the higher gray bins 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.  Observe that this remedy regime can be sustainable, for the reason that beginning and ending mite counts (100 and 104) are primarily the identical.

For one more 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 usually detect zero mites.  On this simulation, as an alternative of indicating whole 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 might be impressed by their low mite counts in April and December, however the colony should still have been affected by a late-season Deformed Wing Virus an infection because of its excessive mite stage in October and November, and won’t make it via the winter.  And even when it did, it might start the season with 157 mites — thrice as many because it began with within the earlier yr.  So this varroa administration technique wouldn’t be sustainable.

Within the simulation beneath (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 might solely kill round 80% of the mites on the grownup bees, and none underneath the cappings.  So for the primary software, since an estimated 56% of the mites can be within the brood, that would depart 44% out on the bees, for which an 80% kill price would lead to an total discount of the mite inhabitants of 35% (44% x 80% = 35%, the determine that the beekeeper would enter).  For every subsequent OAV, the anticipated total efficacy might 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 acquired 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 word that the ending mite inhabitants was practically 4 instances that of the beginning, which might spell bother the subsequent season.

Observe: Randy’s been analyzing information 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, might lead to comparatively low total efficacy, even when repeated at 4-day intervals, particularly if a lot mite immigration is happening (there was average immigration within the above simulation).  Certainly, mite wash counts would possibly even give the impression of no efficacy (as not too long ago noticed by Berry [[3]]).  Observe 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 swap to a Mediterranean California local weather, with a nectar and pollen stream in September and October, and with a bit extra mite immigration throughout late summer time from surrounding neighbors’ hives (Determine 7).

Fig. 7 This San Francisco beekeeper was additionally proactive by treating in mid-March, however acquired 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 time dearth, and he or she obtained 90% efficacy with a double software 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 at the least one mite (darkish crimson space) constructed up to some extent of no return by late November, inflicting all her bees to “disappear” whereas she was distracted by the vacations.  What a bummer of a method to begin the New Yr!

By working 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, primarily based 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 information from others to substantiate its accuracy.

The total 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 kind (or customise in 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 checklist anticipated efficacies of varied therapies).

Trish’s mannequin lacks a few of the customization choices, however can be utilized proper within the area in your mobile phone.

There’s no purpose to be stunned by mites unexpectedly getting uncontrolled in your hives.  By working simulations, you may take a look at out varied mite administration methods in your colonies upfront, adjusting them in your out there remedy home windows, working round honey flows, and rotating totally different therapies to keep away from breeding resistant mites.

Sensible software:  We’ve discovered that probably the most profitable technique is to take care of varroa proactivelyslightly than reactively.  Get forward of the mites as early within the spring as doable, so that you just go into the honey stream with an especially low infestation price, then harvest your honey as quickly as you may after the stream, 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 cell model of my varroa mannequin, and plans to proceed to enhance and replace it (all the time examine for the newest model).  She doesn’t receives a commission for this, so in case you discover it to be helpful, please ship her a donation.  Her web site is [[4]] and her on-line mannequin might be accessed at




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

[4] Trish’s web site:



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