Randy Oliver, with collaboration by Aris Roberts
First revealed in ABJ February 2022
In the summertime of 2020, I examined utilizing Hopguard 3 to regulate varroa. Sadly, the label was not clear, and I didn’t notice that for summer time therapy I used to be allowed to repeat the appliance of the strips. So I ran one other take a look at.
If varroa begins to get forward of you whereas your bees are placing on honey meant for harvest, there are solely two currently-approved remedies to get the mites again below management — formic acid (MAQS or Formic Professional), or Hopguard. I’ve already proven my outcomes for Formic Professional [], and have mentioned with Hopguard’s producer strategies for rewriting the label in an effort to make it extra comprehensible.
The lively ingredient of Hopguard — “potassium salts of hops beta acids” — is extracted (utilizing liquified CO2) from the identical kind of hops flowers used so as to add the bitter taste to beer. Preliminary investigations indicated that bees tolerate hops beta acids about six occasions higher than can varroa [], thus the event of this product as a food-grade “biopesticide” for controlling the mite.
Hopguard has gone by three iterations as a formulated product, every an enchancment over the earlier. The primary limitation for Hopguard and Hopguard II was the brevity of its “residual exercise” [, ], which means that though it brought about a fast kill of mites on the grownup bees, its motion tapered off inside just a few days (and thus wouldn’t have an effect on the remaining mites within the brood as they emerged). The present iteration, Hopguard 3, is an improved formulation that extends the motion for a number of days, and could be very efficacious if utilized to colonies missing brood []. It additionally seems to be gentler on the colony, as evidenced by fewer useless bees in entrance of the hives after software, in comparison with that from Hopguard II (private commentary).
Nonetheless, throughout summer time, when a minimum of 50% of the varroa inhabitants is hidden below the cappings [], Hopguard should be reapplied in an effort to receive good efficacy. Gregorc, after testing it, concluded that three consecutive remedies could be required []. Fortunately, the label permits for Hopguard 3 to be utilized as much as 4 occasions a 12 months, and specifies making use of consecutive remedies two weeks aside (though that interval may use additional exploration, primarily based upon the analysis beforehand cited).
To be able to reply the optimum reapplication interval query, I ran a subject trial starting on the finish of June. As well as, high-school scholar Aris Roberts volunteered to independently acquire information on every day mite drops following August software of Hopguard 3 strips in his hives in Virginia. Though Aris’ information was collected secondly, it’s worthwhile to take a look at it first.
ARIS’ MITE DROP COUNTS
Aris painstakingly counted every day mite drop on the stickyboards of six hives every single day for 37 days. After establishing baseline counts previous to therapy, he utilized Hopguard 3 on the fee of 1 strip per 5 frames of bees, reapplying strips first after 7 days, after which after one other 10 days (Determine 1).
Fig. 1 There was an obvious wide selection of varroa infestation charges of the monitored colonies, primarily based upon their baseline and fast post-treatment mite fall counts. Word how for even the highest-mite colonies, three remedies of Hopguard 3 introduced every day mite drops all the way down to low ranges.
For higher comparability, I summed up all of the mite drop counts for the six hives every day, and in contrast them to the baseline depend from the day earlier than first software of Hopguard 3 (Determine 2).
Fig. 2 By a month from the beginning, three repeated remedies with Hopguard 3 had steadily decreased every day mite drop all the way down to 1 / 4 of the baseline counts. In reply to the query of the residual exercise of the strips, the impact seems to drop off by round 7 days. Information from Aris Roberts.
Sensible software: Hopguard 3 might have prolonged the strips’ residual exercise, however Aris’ information above means that it isn’t doing a lot after per week. So retreatment needs to be accomplished inside two weeks, in an effort to reduce the variety of mites rising from, after which reentering brood cells through the interim. Sadly, the above information had been collected earlier than I wrote the protocol for my very own subject take a look at in California.
SUGGESTIONS FOR BEEKEEPERS WANTING TO DO RESEARCH
Aris exhibits us how even a teenage pastime beekeeper can acquire very helpful information of use to the beekeeping group. For extra info on the way you or a gaggle can carry out significant analysis yourselves, I’ve not too long ago posted the slides for a presentation that I put collectively on tips on how to carry out bee analysis at []. I’m typically comfortable to assist beekeepers with experimental design and protocols, and am prepared to put up good analysis by others at ScientificBeekeeping.com.
A FIELD TRIAL IN CALIFORNIA
Not but realizing the optimum retreatment schedule for Hopguard 3, I consulted with Fabiana Ahumada, now at BetaTec Hop Merchandise, who has been regularly concerned with the event of Hopguard since its early testing on the USDA Tucson Lab. We determined that I ought to take a look at three purposes at both 7- or 14-day intervals.
MATERIALS AND METHODS
I began the trial towards the top of the honey circulate in late June, whereas there was nonetheless some incoming nectar and pollen. The climate was highly regarded and dry (Determine 3). Sadly, we had by that point managed varroa in most of our yards, and the one colonies with mite ranges excessive sufficient for gathering efficacy information had been a gaggle of untreated hives in my dwelling yard, consisting principally of “potential breeder queens” that had gone with out mite therapy for over a 12 months, however now had mite counts going up. I presciently wrote in my notes on the time that “the speed of mite improve in these colonies could also be depressed relative to colonies that had not beforehand exhibited some extent of resistance to mite buildup.” As we’ll see, this concern turned out to be legitimate.
Fig. 3 The trial was run throughout scorching climate in July and August, with every day highs usually within the 90s F.
All colonies had been in double deeps, headed by 2nd-year queens. Colony power ranged from 15-20 frames coated with bees (they’d earlier been contracted to forestall swarming), all with brood in each containers, and loads of honey within the higher field.
We carried out pretreatment mite washes on 27-28 June, taking degree ½- cup samples of bees from frames adjoining to brood within the higher brood chamber, mechanically agitated them, and recorded the variety of mites. I sadly may give you solely 18 hives with excessive sufficient mite counts to make use of for the trial. I assigned remedies in a randomized block design, blocked by beginning mite depend, with 7 hives within the weekly software group, 7 within the 14-day software group, and 4 hives with midrange counts [] within the Management group. We took follow-up mite wash counts after one and two full bee brood cycles after first software of the strips, and once more after 66 days, in an effort to decide the long-term impact of therapy. The experimental design is proven in Desk 1.
We utilized the primary therapy to all hives the day after taking the primary mite counts (Determine 4).
Fig. 4 Utility of Hopguard 3 strips. We utilized them (generously) as per label directions of 1 strip per each 5 frames of bees. Most colonies obtained 4 strips, however the few with solely 15-frame beginning power obtained solely three. We eliminated the earlier strips at every retreatment.
No mite therapy is totally innocent to the bees. The producer cautions to smoke the highest bars to trigger the queen to maneuver out of the best way of a sticky strip as you insert it. If a bee will get rolled by a strip through the insertion course of, we’ll discover it useless on the touchdown board the following morning (Determine 5).
Fig. 5 The unlucky wetted bee within the heart of the picture will probably die from being rolled by an inserted strip. Nonetheless, we’ve utilized Hopguard to many hives, and have but to see a queen get killed.
Utility of Hopguard strips initially causes the bees to maneuver broodrearing away from the strips (Figures 6 & 7).
Fig. 6 Colonies are likely to shift their brood rearing away from contemporary strips.
Fig. 7 However after a few weeks, as soon as the strips’ odor had dissipated, the bees will resume broodrearing below them, and finally begin chewing away on the strips to take away them.
I didn’t carry out precise measurements, however my visible inspections indicated that there was extra brood, particularly open brood, within the Controls than within the handled colonies throughout therapy. This obvious suppression of broodrearing might assist the therapy to work in opposition to varroa (just like formic acid, thymol, and amitraz remedies, which additionally suppress brood rearing to some extent).
The honey circulate started truly fizzling out after beginning the trial, so colony populations had already peaked. It was laborious to inform, however there seemed to be an impact upon the cluster dimension from therapy. On the three-week assessments, the Management colonies coated all 20 frames of their hives, whereas the clusters in lots of the handled colonies had shrunken considerably. After I reapplied the Hopguard strips to the handled colonies, I usually needed to transfer the substitute strips inward to maintain them inside shrinking clusters (Determine 8).
Fig. 8 The clusters tended to shrink a bit within the handled colonies. On the left is a typical colony instantly after software of the primary therapy. In subsequent remedies (proper), the clusters usually now not coated the strips. Regardless of this short-term impact, the colonies recovered rapidly.
MY MISTAKE IN USING MITE-RESISTANT COLONIES
Let’s check out the mite wash counts for all of the hives over the course of the trial (Determine 9).
Fig. 9 Both software routine lowered the infestation fee of the grownup bees in each the brief time period or the long run. Three remedies with Hopguard 3 undoubtedly knocked the mites again, however neither therapy zeroed out mite wash counts. However why the heck did mite counts additionally go down within the untreated Controls after that point?
Sensible software: By two weeks after therapy, any mites that had been initially hidden within the brood would have emerged, after which they typically spend just a few days feeding on nurse bees earlier than they reenter a brood cell in an effort to reproduce. The query then is, would retreatment at 7 days end in greater efficacy than at 14 days? To my shock, it didn’t seem to make a lot distinction.
It seems that it was a mistake for me to have used rejected potential breeder colonies (those who had mite counts growing of their second season) for many of the hives within the trial, since all 4 Management hives finally began to convey their counts down on their very own (some exhibited sturdy uncapping and VSH behaviors; Determine 10). So this screwed up the anticipated improve of mite counts within the Management group, which prevented me from performing any significant efficacy calcs. Reside and study! This trial must be repeated utilizing nothing however demonstrated non-resistant colonies.
Fig. 10 As soon as their infestation charges obtained above a sure degree, a number of the Management colonies exhibited sturdy uncapping and/or “varroa delicate hygiene” (VSH) conduct, which apparently was efficient at lowering their infestation charges. I’ve seen different resistant colonies do the identical — placing it into gear if varroa reaches a sure degree.
Sensible software: After 5 years of sturdy choice for mite resistance, roughly 10% of our colonies require no mite therapy in any way. When testing any miticide, I usually use high-mite colonies that clearly present no mite resistance. Sadly by the point I began this Hopguard trial, I’d already used up any high-mite colonies for different experiments, and thought that I may use some rejected potential breeders. Looking back, that was not a good suggestion!
So maybe the very best interpretation of the information is to take a look at the p.c adjustments within the common infestation charges for every therapy group over time (Determine 11).
Fig. 11 So, what with the screwy Management group, can we salvage any significant info from this subject trial? On this graph, I present the proportion of every group’s beginning infestation fee (normalized to 100%) at every subsequent time level. At Day 21, by which level the depend within the Management group had gone up by 27%, the Hopguard 3-treated teams had gone down by round 80% — not unhealthy in any respect! []. Most tellingly, by the top of the trial at Day 66, the Hopguard-treated colonies nonetheless had mite infestation charges of round a 3rd of what they began with. (Remember that the trial wrapped up in early September, when mite counts typically rise considerably.)
Though I used to be not in a position to calculate a respectable determine for efficacy, I used to be impressed by Hopguard 3 for being a relatively-gentle mite therapy that could possibly be used throughout scorching climate with out concern for queen loss or honey contamination.
Sensible software: Just like formic acid or oxalic dribble, Hopguard is fast-acting and extremely efficacious on the “phoretic” mites on the grownup bees, which is a vital consideration while you need to scale back a excessive mite infestation fee rapidly.
Primarily based upon Aris’ findings that the strips are now not a lot lively after per week, the Day 66 infestation charges had been taken a month to month-and-a-half after the remedies wore off, so the remaining mite populations would have had time to rebuild. These findings recommend that if it’s worthwhile to knock again varroa when you’ve obtained honey on the hive, two purposes of Hopguard 3 two weeks aside present fairly good management.
A single software of Hopguard 3 could also be sufficient if a colony is broodless (I’ve efficiently used it myself at the moment with good success), nevertheless it clearly takes a minimum of two purposes through the summer time if a colony has an lively broodnest. The general efficacy from making use of the strips each two weeks, relatively than weekly, seemed to be about the identical. This comes as a shock to me, since I might have guess that the three weekly purposes would have accomplished a greater job. So it seems like three purposes may not be price the fee or effort (it does take a little bit of time to use and take away the strips).
Sensible software: Attributable to my mistake of utilizing colonies with a level of mite resistance, please don’t think about this to be any form of definitive trial of Hopguard 3. However primarily based on this too-small and confounded take a look at, I’d think about repeated therapy with Hopguard 3 to be a viable non-contaminating, food-grade, and “pure” “knockback” therapy for double-deeps whereas harvestable honey is on the hive. Because it seems to be comparatively mild on the colony, Hopguard 3 seems to be one other priceless instrument in our arsenal in opposition to varroa.
Due to Brion and Alice Dunbar for his or her help in my subject trial.
CITATIONS AND NOTES
 Rademacher, E., et al (2015). The event of HopGuard® as a winter therapy in opposition to Varroa destructor in colonies of Apis mellifera. Apidologie 46(6): 748-759.
 DeGrandi-Hoffman, G, et al (2012) The consequences of beta acids from hops (Humulus lupulus) on mortality of Varroa destructor (Acari: Varroidae). Experimental and Utilized Acarology 58(4): 407-421.
 Vandervalk, L, et al. (2014) New miticides for built-in pest administration of Varroa destructor (Acari: Varroidae) in honey bee colonies on the Canadian prairies. Journal of financial entomology 107(6): 2030-2036.
 Nasr, M, et al (2014) An efficient improved software technique of HopGuard for varroa management in Canada. Obtainable on-line.
 Gregorc, A, et al. (2018). Toxicity of chosen acaricides to honey bees (Apis mellifera) and varroa (Varroa destructor Anderson and Trueman) and their use in controlling varroa inside honey bee colonies. Bugs, 9(2), 55.
 When testing for efficacy of varroa remedies, utilizing mite washes because the metric, I’ve discovered that the p.c mite discount is normally considerably higher for higher-mite hives (https://scientificbeekeeping.com/mite-control-while-honey-is-on-the-hive-part-2/). This presents an issue if Management colonies are chosen randomly, since Controls that begin with very excessive mite counts will usually collapse previous to the top of the trial, however in the event you begin with solely low-mite Controls, they actually can’t be thought-about to be respectable controls. So for this trial, I used the 4 hives with mite counts within the center as Controls.
 If I had been attempting to promote the product, I might have tossed any subsequent information, since I may have claimed 85% efficacy at the moment level.