# Towards integrated control of varroa: 2)comparing application methods and doses of ox



## JWChesnut (Jul 31, 2013)

Towards integrated control of varroa: Part 2) comparing
application methods and doses of oxalic acid on
the mortality of phoretic Varroa destructor mites
and their honey bee hosts


Hasan Al Toufailia, Luciano Scandian & Francis L W Ratnieks (2015) Towards
integrated control of varroa: 2)comparing application methods and doses of oxalic acid on the
mortality of phoretic Varroa destructor mites and their honey bee hosts, Journal of Apicultural
Research, 54:2, 108-120, 
DOI: 10.1080/00218839.2015.1106777
To link to this article: http://dx.doi.org/10.1080/00218839.2015.1106777

ORIGINAL RESEARCH ARTICLE

Received 16 April 2014; accepted 6 October 2015

In the past two decades, the parasitic mite Varroa destructor
has become harder to control with synthetic acaricide chemicals due to genetic resistance. We determined the efficacy of the natural chemical oxalic acid (OA) in killing phoretic mites on adult worker bees under field conditions in southern England. We compared three OA application methods (trickling, spraying, and sublimation) at three or four (sublimation) doses, using 110 broodless colonies in early January 2013. Treatment efficacy was assessed by extracting mites from samples of c. 270 worker bees collected immediately before and 10 days after treatment. All three methods could give high varroa mortality, c. 93–95%, using 2.25 g OA per colony. However, sublimation was superior as it gave higher mortality at lower doses (.56 or 1.125 g per colony: trickling 20, 57% mortality; spraying 25, 86%; sublimation 81, 97%.). Sublimation using 2.25 g of OA also resulted in 3 and 12 times less worker bee mortality in the 10 days after application than either trickling or spraying, respectively, and lower colony mortality four months later in mid spring. Colonies treated via sublimation also had greater brood area four months later than colonies treated via trickling, spraying, or control colonies. A second trial in December 2013 treated 89 broodless colonies with 2.25 g OA via sublimation to confirm the previous results. Varroa mortality was 97.6% and 87 (98%) of the colonies survived until spring. This confirms that applying OA via sublimation in broodless honey bee colonies in winter is a highly effective way of controlling V. destructor and causes no harm to the colonies


----------



## Robert Holcombe (Oct 10, 2019)

There is also an article out there supporting a 99.7% efficacy for two winter treatments (brood-less or a little brood?) fourteen days apart. OAV is a major IPM tool for me, especially in the Fall. What neither article or any article I can find deals with the onslaught of the Varroa, Fall horizontal migration and robbing affects. Around me, it is huge.


----------



## msl (Sep 6, 2016)

> What neither article or any article I can find deals with the onslaught of the Varroa, Fall horizontal migration and robbing affects


Sakofski, F, et al (1990) Seasonality of honeybee colony invasion by Varroa jacobsoni Oud. Apidologie 21:547–550

Greatti M, Milani N, Nazzi F (1992) Reinfestation of an acaricide-treated apiary by Varroa jacobsoni Oud. Exp Appl Acarol 16:279–286

Mangum, WA (2011) Varroa immigration and resistant mites. ABJ 151(5): 475-477.

Frey E, Schnell H, Rosenkranz P (2011) Invasion of Varroa destructor into mite-free honeybee colonies under the controlled conditions of a military training area. J Apic Res 50:138–144.

Frey E, Rosenkrantz P (2014) Autumn invasion rates of Varroa destructor (Mesostigmata: Varroidae) into honey bee (Hymenoptera: Apidae) colonies and the resulting increase in mite populations. J Econ Entomol 107:508–515.

Peck, D.T.; Seeley, T.D. (2019) Mite bombs or robber lures? The roles of drifting and robbing in Varroa destructor transmission from collapsing honey bee colonies to their neighbors. PLoS ONE 2019, 14, e0218392.

and of course Randy olver has some good stuff (but not peer reviewed studys)
http://scientificbeekeeping.com/the-varroa-problem-part-16b/
http://scientificbeekeeping.com/mite-drift-quantification/


----------



## Michael Palmer (Dec 29, 2006)

I guess efficacy might depend on where the apiary is located. I vaped tow years, in early November when the colonies were broodless. In th spring after the second year, the mite levels were sky high. I believe that in my climate, when the colonies are broodless, the clusters are tight and the vapors don't penetrate th clusters. I also tried in September..three times a week apart. Mite counts of around 20 went up or stayed the same, a week after final vape.


----------



## Robert Holcombe (Oct 10, 2019)

Being retired and a hobbyist I spend more time being a Contrarian. I have seen different results from OAV treatments over the last two years, good results; been using OAV since 2016. It is likely a related to different approaches when using OAV. I do use multiple OAV treatments and Varroa-drone trapping and tested a brood-break treatment approach. I have only lost 1 colony out of 21 colonies in two winters now (multiple hive status). Most of my problems seem to be Spring queen issues. During the "bombing" period I treat every 4-5 days to protect the winter brood (un-verified). 

What I have been trying to explore is the variations in application performance as a result of application timing and hive variations with nine colonies. The impact of Fall Bombs is being well reported now but how to deal with them is not. My best answer so far is a long term or multiple Fall treatments during the invasion until the count is really down as the hive goes brood-less. In my little apiary it has taken and still takes a lot work just learning about identifying the Varroa problem. I gave up on alcohol washes.

I have not been able to create a cook-book IPM receipt so far. I am limited in what I will use - house rules. The variations identified with nine colonies range from a growing nuc all summer to a"very resistant" colony and to a colony that underwent a complete hive brood break with post-break OAV treatments, to an outlier loaded with mites and requiring twice the amount of time to hammer the huge Varroa population ( missed identifying this one earlier). Plotting each hives' 3rd or 4th day Varroa Dead Drop Count (VDDC) results against a calendar date after treatment shows the variations. Summing all the hives VDDC produces a clear plot of the invasion dates and likely the drop of in the amount of brood rearing. The one brood-break colony did not show a large resident colony of Varroa in late September after supers were removed - 291 total for a large foraging colony. The 291 is a total season value and likely includes some "traveling mites" as the robbing was starting up. Around here, with my home grown bees and purchased queens, Varroa Bombs seems to dominate. Two years running with Winter OAV treatments I have yet to find a hive with significant Varroa via sample capped drone checking or using the brood-break during the summer. I may have missed one hive or they started robbing early.


----------



## Robert Holcombe (Oct 10, 2019)




----------



## BernhardHeuvel (Mar 13, 2013)

Michael Palmer said:


> I vaped tow years,


Nice. Michael tries vapping while I tried Amitraz treatment this year.  

Definitely kills mites. Average 5.000-8.000 mites per hive this year. Don't know why, but this year there where a lot of mites in 2/3 of the hives, while the other third had almost no mites at all. Very unusual. Already in Spring. (Not only in my hives but virtually all hives that I came across throughout Germany and neighboring countries, throughout the year.)


































Some important observation I made.

What I observed is, that mites crouched into cells that were ready to be capped. Not unusual. But what was highly unusual: the mites started feeding on the larvae before the cells were capped. Never observed something like that before. Anyone elses seen this? Is that a change in behavior I've observed?


----------



## Oldtimer (Jul 4, 2010)

Ouch that looks terrible Bernhard, poor little larvae!

How do you know they were feeding on the larvae pre capping? I had understood they eat royal jelly till capping.


----------



## BernhardHeuvel (Mar 13, 2013)

Varroa mites don't eat royal jelly. In fact they hate it. Bee larvae are fed royal larvae only for the first three days, after that they get another diet from nectar+pollen jelly. 

Mites dive down into the brood food (not royal jelly) and "snorkel" there to hide from the bees. 

I can tell they start sucking because they cling to the larvae and not hiding in the brood food jelly. I could also visibly see the hole they made into the larvae. The feeding spot.


----------



## BernhardHeuvel (Mar 13, 2013)

I just hope they don't generally change their behavior. Because damage would be much greater if the mites start feeding earlier on the larvae. 

I am unsure, what reasons made them do so. Is this a reaction to treatments? Is this a reaction to protein deficits? Do they feed earlier to prolong the reproduction phase? And get more mated daughters by that? I can't say.


----------



## Oldtimer (Jul 4, 2010)

Very interesting questions you raise!!


----------



## AHudd (Mar 5, 2015)

Dang, that third photo made me gasp.

Alex


----------

