Thymol — a New Utility Manner? Section 1

As our summers get warmer, one of the “herbal” remedies towards varroa have problems, because the hostile results of each formic acid and thymol building up at top temperatures. Thus I’ve been experimenting with decreasing and increasing the discharge price of oxalic acid and formic acid. However how about thymol — may just we prolong its launch price too? This summer season I resumed a little analysis that I’d initiated again in 2017.

Thymol is a well-proven “herbal” miticide, rather effectively tolerated by way of the bees. My sons and I exploit thymol in rotation with oxalic acid and formic acid, with every miticide being suitable to be used all over other “remedy home windows” (Determine 1).

Fig. 1. I created the above generic chart (regulate the dates on your space) to show the most efficient remedy home windows for varroa control, in addition to essentially the most suitable energetic components to use all over the ones home windows. We’ve discovered that within the California weather, it generally calls for no less than 4 remedies in keeping with season to care for low varroa ranges (in non-resistant inventory). To steer clear of the evolution of miticide-resistant varroa, all of us will have to rotate other energetic components.

Thymol, because of its transient suppression of broodrearing, is acceptable to be used if you’ll be able to get harvestable honey off the hive earlier than mid-August. It can be used to each management mites and suppress colony buildup previous to swarm season.

In my state of California, there may be just a unmarried registered thymol product — Apiguard, with particular directions as to how it may be implemented. We’ve been pleased with Apiguard, however that’s to not say that there will not be a extra bee- and beekeeper-friendly solution to practice this shown miticide. Some obstacles of Apiguard are that:

An area will have to be equipped underneath the hive duvet, because of this that for the ones people who use migratory covers, a spacer rim of a few type will have to be equipped (Determine 2).

Fig. 2. The one thymol product licensed to be used in California is Apiguard “gel,” right here implemented in a spacer rim. My sons and I’ve effectively used it for a few years in rotation with different remedies, principally all over sizzling climate in August, once we don’t thoughts its transient suppression of broodrearing all over our dearth length.

For complete efficacy, the remedy will have to be repeated, which takes additional hard work. We’d a lot favor a remedy that calls for just a unmarried software.
The label now not lets in for putting the product between the brood chambers, which might be essential for software all over cool climate.
Utility above the brood chamber is most effective efficacious if the colony is robust sufficient to take away the remedy from the cardboard above the highest bars (my very own commentary). A remedy that may be implemented between the brood chambers could be of serious receive advantages.
Even supposing Apiguard will also be implemented at day by day highs of as much as 105°F, our summers are getting hotter (Determine 3), and all over our optimum remedy window in August this yr, it were given even warmer than that.

Fig. 3. The blue trendline displays the rise in California’s reasonable August top temperature over my lifetime. It’s no longer simply that I’m growing old — it truly is getting warmer! You’ll plot identical charts on your space at https://www.ncei.noaa.gov/get entry to/tracking/climate-at-a-glance/statewide/time-series.

Most likely most significantly, once we practice Apiguard as in keeping with the label, the broodnest is a great deal impacted — the vapor kills the eggs and younger larvae at once underneath the remedy (which the nurses then cannibalize), after which the colony reestablishes a divided and lowered broodnest to each side of the remedy.

Sensible software: Apiguard is a smart product, however I believe that there may well be even higher software strategies suitable for our stipulations and colony control. However we beekeepers are legally precluded from tweaking the applying strategies specified at the label, or from the use of generic thymol to use by way of other strategies.

“Off-Label” use of thymol

Sensible software: Varroa remedies are registered as insecticides. When a producer is going throughout the tortuous and dear technique of registering a pesticide, they will have to supply a particular set of licensed software directions. Any deviation from the ones directions is a contravention of the legislation.

The placement is extra affordable with medications: “From the FDA point of view, as soon as the FDA approves a drug, healthcare suppliers typically would possibly prescribe the drug for an unapproved use after they pass judgement on that it’s medically suitable for his or her affected person” [[1]]. That is known as “off label” use, and is quite common in drugs.

Docs and their sufferers are allowed to experiment and find out about how best possible to make use of medicinal medication below other instances, and for not-yet-registered makes use of. Sadly, this freedom does no longer practice to registered miticides, so we beekeepers (and even our veterinarians) aren’t allowed to tweak software how to account for the wide variety of scenarios that we stumble upon in beekeeping.

EPA’s refusal to imagine granting us beekeepers an Personal Use Exemption for the natural acids and thymol frustrates me, because it prevents us from studying find out how to practice those secure and affordable generic elements to our colonies, as an alternative forcing us to buy and apply the inflexible label directions for dear registered formulated merchandise.

Right here’s the rub: As defined by way of USDA [[2]]: “Relative to miticide makes use of on agricultural vegetation, programs of varroacides to bee colonies are regarded as a minor use that would possibly not permit for registrants to justify the prices to increase varroacides and break-even on such investments, given the small relative marketplace possible.” So we will be able to’t be expecting producers to deliver a number of custom designed varroa management merchandise to marketplace.

A plea to our nationwide organizations: Registrants are reluctant to move throughout the tedious technique of updating their labels, so we beekeepers are caught between a rock and a difficult position. So far as EPA’s mandate to steer clear of unreasonable possibility to guy or the surroundings, beekeeper use of generic off-the-shelf formic, oxalic, or thymol would pose no such dangers. The federal government of New Zealand correctly known this, and gave beekeepers an exemption to make use of those “herbal” merchandise for varroa management on the other hand they need. I counsel that our nationwide organizations method our senators and congressional representatives to legislate an Personal Use Exemption very similar to New Zealand’s.

The truth is that because of our restricted arsenal of licensed formulated varroa-control merchandise, many beekeepers have sadly develop into “pesticide scofflaws.” I gotta stroll a high-quality line with my analysis, which I do for the good thing about all, slightly than for benefit. I download Pesticide Analysis Authorizations from my State’s division of pesticide law, and submit my findings as medical analysis most effective — It’s not that i am in any respect suggesting that beekeepers use any unregistered product, or no longer apply label directions precisely (I gotta duvet my donkey).

Thymol merchandise for varroa management

There are 3 major thymol merchandise registered in North The usa for varroa management — Apiguard, ApiLife Var, and Thymovar. Handiest two are registered within the U.S., and most effective Apiguard in California. All paintings by way of the evaporation of thymol vapors from an inert matrix, and phone for putting the remedy a couple of inches from the brood. Thymol is typically really useful for software all over average ambient temperatures — generally between 20-25°C (~68-77°F), even if some product labels permit software at upper temperatures. All specify to not practice whilst honey for harvest is being produced.

One widely-used product is ApiLife Var, which is a mix of thymol, eucalyptol, menthol, and camphor, impregnated right into a vermiculite wafer. I attempted ApiLife when it was once first launched within the U.S. (learn my record at [[3]]), and located that it was once extra frustrating to the bees than directly thymol, most probably because of the extra crucial oils. However it can be this extra inflammation to the bees — and mites — that provides it larger efficacy at low temperatures, or promotes its distribution all through the cluster.

Thymovar, additionally registered in a variety of international locations, is a cellulose sponge strip impregnated with directly thymol crystals.

Apiguard makes use of a gel-like matrix of water and polyacrylate (corresponding to is utilized in diapers) to droop high-quality crystals of thymol, which slows the evaporation price. In my enjoy, its efficacy depends on the bees bodily wearing away the debris, slightly than easy evaporation.

I’m additionally conscious that a variety of beekeepers combine up their very own “homebrew” thymol formulations, occasionally with the addition of alternative crucial oils. I’ve examined a few of these homebrews (which will also be efficacious), however am maximum fascinated about directly thymol.

Figuring out Thymol

Thymol seems to impact the mites by way of publicity to its vapor. It no longer most effective reasons direct toxicity, however might also worsen them, or in all probability impact their crucial sense of scent. As well as, thymol vapors could cause bees to have interaction in additional intense cleansing conduct, and even brood elimination. But it surely’s transparent that thymol has a a long way larger hostile impact upon varroa than it does upon the bees (particularly grownup staff, who “get used to it”).

Opposite to well-liked trust, thymol isn’t extremely unstable — should you put a couple of thymol crystals out in a tray to evaporate, it takes many days for them to take action, even at broodnest temperature. It’s truly tricky to seek out information on thymol’s vapor drive, however apparently to be a long way much less unstable than water, kerosene, or in all probability even vegetable oil. If I stick my nostril into the mouth of a jar of thymol crystals I will scent a faint smell; if I do the similar with a jar of menthol crystals, the smell is intense, and my eyes and lungs burn.

The gradual evaporation of thymol is suffering from temperature, in addition to the crystals’ publicity to air glide (which will also be significantly greater by way of the fanning of the bees). With Apiguard, the thymol is flooring into high-quality crystals, which might be suspended in a mix of water and absorbent globules of sodium polyacrylate — little or no thymol in fact dissolves into water. Thus, the bees will have to in fact take away the globules of gel to reveal the surfaces of the crystals to evaporation.

With Thymovar, the crystals are extra uncovered, and will evaporate extra briefly (occasionally inflicting over the top brood problems in sizzling climate).

Sensible software: I puzzled whether or not there was once differently to use thymol, that prolonged its launch price to steer clear of the want to reapply the remedy, that didn’t inspire propolization, that didn’t require the addition of a rim, and in all probability be a matrix that the bees would take away themselves after remedy (corresponding to came about once I implemented a low dose of Apiguard between the brood chambers on an index card [[4]]). Preferably, a great remedy would no longer be excessively frustrating to the bees, and would no longer close down broodrearing for a protracted length.

Response to the supply matrix by way of the bees

Bees are repelled by way of a robust smell of thymol, and can try to enclose it in a curtain of propolis. However as soon as its outgassing slows, the employees appearing as “housecleaner/janitors” will both encase it in propolis (Determine 4), or select off items of the matrix and take away it from the hive (Determine 6).

Fig. 4. If the cleaner bees are not able to chunk away a matrix that smells of thymol, they are going to both construct a wall of propolis round it, or encase it in a layer of propolis as above.

Thymol in Store Towels

Some of the supply matrices for thymol that I attempted was once the economic beekeepers’ standby — the blue store towel. I discovered {that a} saturated answer of thymol may well be simply made by way of dissolving it in denatured alcohol (particularly if the alcohol was once warmed) (Determine 5).

Fig. 5. A gram of thymol readily dissolves right into a milliliter of denatured alcohol, leading to ~2 mL of a saturated answer. The answer wicks readily into a store towel. I then simply laid the towels out to dry for an hour, during which time (no less than in our California dry air) the alcohol had all evaporated. Because of the low vapor drive of the thymol, there may be just about no weight lack of thymol. I then positioned the dried towels into an hermetic container for garage.

I implemented the towels to check for elimination and hostile results. I positioned part towels (containing a standard dose of ~12 g of thymol), in sizzling climate, both between the brood chambers, or in rims underneath the hive duvet (Determine 6). It was once briefly obvious that 12 grams on a towel in the midst of the cluster was once an excessive amount of, because the colonies roared and bearded out the entrances (I used to be afraid that they could abscond). That intense a dose additionally ended in some elimination of sealed brood. 1 / 4 towel (containing ~6 g of thymol) was once higher tolerated.

Fig. 6. Part a thymol-impregnated store towel in a rim. In the beginning the bees are repelled by way of the fumes and fan them away. However as quickly because the depth of vapors drops, they hastily take away each and every hint of the towel, infrequently propolizing it.

What was once attention-grabbing to me was once the unusually fast price that the bees evaporated the thymol from the towels positioned in the midst of the cluster. Not like with Apiguard or Thymovar, it was once like a “flash” remedy, and after a few days I may just slightly scent thymol in the rest towels. It seems that, the temperature of the broodnest, coupled with the sturdy fanning, leads to fast thymol evaporation from this skinny matrix, and janitor bees then briefly take away the rest mildly scented towels.

A chum attempted the towels in a couple of colonies, taking earlier than and after mite counts. The consequences have been {that a} part towel positioned in the midst of the cluster ended in really extensive mite relief, however was once very nerve-racking to the colony. 1 / 4 towel was once a lot better tolerated, however required a repeat software for efficacy. The towels positioned in a rim above the hive gave variable effects.

Sensible software: The take house is {that a} store towel, because of its top ratio of floor space relative to quantity, lets in for too-rapid launch of the thymol for many functions (however could be utilized in broodless colonies [[5]]). This thus raises the query of whether or not a cellulose matrix thicker than the Thymovar sponge would permit for a extra managed and prolonged launch of thymol vapors because the thymol vapor from the inner of the matrix slowly subtle to the skin.

Removing and dispersion of thymol matrices by way of the Bees

Sensible software: I’ve discovered that once Apiguard is positioned above the colony, except the bees bodily take away Apiguard from the cardboard it shows low efficacy towards varroa. I believe that the method of bodily shipping throughout the cluster is essential, since it will divulge the surfaces of the chewed debris of the matrix to permit for evaporation of the thymol. So the most important query is, do the cleaner bees drag the debris down throughout the brood space (thus exposing the mites there to the fumes), or do they steer clear of that space?

We made a captivating commentary some years in the past once we had stickyboards below colonies handled with store towels infused with oxalic acid and glycerin (Determine 7).

Fig. 7. When the housecleaner bees chewed away store towels infused with oxalic acid and glycerin, the debris of particles just about all wound up piled at the stickyboards, heaped simply throughout the front, suggesting that the janitor bees took routes that have shyed away from the broodnest.

Curious, we not too long ago arrange a hive to decide whether or not the cleaner bees do the similar with particles containing thymol. We put a stickyboard below a colony, and implemented two other thymol remedies at the best bars between the brood chambers — one a part store towel impregnated with thymol, the opposite scoops of Apiguard (combined with a fluorescent tracer). We positioned every remedy one by one on other facets of the hive. I sought after to peer whether or not the bees would once more lift the particles to the entrance of the hive, or whether or not it will be taken (or fall) down throughout the broodnest (Determine 8).

Fig. 8. We positioned fluorescent-tagged Apiguard at the best bars of 1 aspect of the broodnest (the a long way aspect on this photograph), and a part thymol-infused store towel at the close to aspect. This symbol (below UV + herbal lights) was once taken 4 days later, confirming that a number of debris of every matrix one way or the other sifted their manner at once down throughout the broodnest, slightly than being performed clear of the brood (the gray-bluish particles within the foreground is from the store towel). This dispersion of the matrix throughout the broodnest most probably will increase the publicity to the mites to the thymol vapors, because the thymol would evaporate hastily from the surfaces of the small debris of particles as they have been carried (or sifted their manner) down.

Prolonged-Liberate Thymol?

Notice that all of the registered thymol merchandise name for repeated programs to succeed in excellent efficacy. If shall we get a hold of a remedy that prolonged the discharge of thymol even longer than does Apiguard, we may be able to get by way of with just a unmarried software.

This were given me questioning whether or not shall we use a thicker cellulose matrix than utilized by Thymovar, to throttle the evaporation price over an extended time frame, permitting us to get by way of with a unmarried software. And would a matrix that inspired bodily shipping by way of the janitor bees building up efficacy?

A Thicker Matrix

I used to be intrigued by way of the Homasote insulation board (made out of recycled newspaper) utilized by NOD to make its MiteAway II pads. So again in 2017, assisted by way of Tara McKinnon, we experimented with it. Different beekeepers have been dissolving thymol in vegetable oil or Crisco for his or her homebrews, so I puzzled whether or not the thymol would paintings higher if canola oil was once added to gradual evaporation, or in all probability lend a hand it to stick with the bees’ our bodies. So we made up a 4-way grid of 16 other thymol and canola oil concentrations (Determine 9), dissolved them in ethanol, and saturated 1” sq. blocks of Homasote with them (Determine 10).

Fig. 9. We attempted 16 other ratios of thymol and canola oil. The quantity of every substance that may stay in every 1” sq. block of Homasote is proven above. The ones quantities ranged from 0.6-2.4 g of thymol, and nil to one.9 g of oil.

Fig. 10. Getting ready the take a look at blocks. Those have simply absorbed the answers.

We then positioned units of 16 take a look at blocks into 4 hives between the brood chambers (Determine 11). This allowed us to check for a way the bees answered to the depth of thymol, in addition to to the addition of oil.

Fig. 11. Notice the variability of oil saturation, as indicated by way of the darker colour of the blocks containing extra oil. There have been thymol crystals at the surfaces of all of the blocks rather than essentially the most oil-saturated.

Tara then opened the hives day by day, and recorded how the bees have been responding to the blocks, so far as avoidance, chewing, or propolization (Determine 12).

Fig. 12. There was once in fact colony-to-colony variation, however we discovered that the bees tended to propolize blocks containing extra oil, while after a couple of days they began chewing away blocks with much less oil.

This discovering steered that blocks of Homasote containing thymol by myself (no oil), may paintings effectively as an extended-release cousin of the Thymovar strips.

transferring forward to 2022

I shelved the above concept till this yr. Since I’ve not too long ago been experimenting with extended-release formic and oxalic acids, I figured that I must select again up on my experimentation with thymol and Homasote. However I’m out of house, so that you’re going to have to attend till subsequent month to peer what we discovered.

Citations and notes

[1] Figuring out Unapproved Use of Authorized Medicine “Off Label” | FDA

[2] Varroacide Registration : USDA ARS

[3] IPM 7 Combating Varroa The Arsenal: “Herbal” Remedies – Section 2 – Medical Beekeeping The appliance directions at the label are unusually complicated, however Veto Pharma has some helpful movies on its site.

[4] The Finding out Curve – Section 3: The Herbal Miticides – Medical Beekeeping

[5] Chiesa, F & M D’agaro (1991) Efficient management of varroatosis the use of powdered thymol. Apidologie 22(2): 135-145.