Varroa under the micrscope

[ShinySideUp]

I wiped off my removable floor today of the hundreds of varroa mites that have fallen due to OA trickling and thought I'd put one under the microscope; what horrible little beasts they are! They have hairs and shiny bodies, lots of legs and look generally yucky (technical term, that). As I was focussing I noticed that the action of the depth of field changing was making two of the legs look like they were moving...no, they were moving; damn thing was still alive!

Which brings me to a question that a search of the web seems reluctant to cough up an answer -- how exactly does oxalic acid kill varroa mites?

The most common answer seems to be that the acid dissolves the mites' mouth parts so they starve to death but that doesn't really explain fully why they fall of the bees while still alive, unless they become weak I suppose.

Is there a definitive answer that someone knows of?

 

[For want of a better word]

The spicules of OA crystals pierce their black hearts !

Nadalik Lowen ha blydhen nowydh da

Nos da

 

[ShinySideUp]

 

[viridens]

Does this help?
Quoted from http://www.varroamilbe.ch/Abstract_Effect-of-oxalic-acid-on-Varroa-mites.pdf

Oxalic acid uptake:
In the reports at hand, the effects of oxalic acid on varroa mites have been studied over a period of
12 years with simple methods. When feeding bees with honey syrup it was apparent that bees
refrain from ingesting oxalic acid with the food and thereby that oxalic acid uptake by the varroa
cannot happen via the bees system. When examining the feet (tarsus) of fallen-off but still alive
mites under a microscope, major accumulations of oxalic acid crystals could be found at the
outermost segment of the tarsus with the moist adhesive pad. The mites died within 24 hours of the
examination. During this time it was noticeable that the oxalic acid crystals at the adhesive pad of the
mites dissolved and penetrated the pad. This was accompanied by a simultaneous cease in life signs
in the mites. This observation leads to the hypothesis that oxalic acid crystals are collected in great
numbers with the adhesive pads on the mites feet, where they then dissolve within a few hours and
penetrate the body of the varroa via the membranes in the adhesive pads. This hypothesis is also
supported by the fact that the same observation can be made, regardless of the method of
application (spraying, trickling or vaporizing).

 

[Hivemaker.]

When feeding bees with honey syrup it was apparent that bees
refrain from ingesting oxalic acid with the food and thereby that oxalic acid uptake by the varroa
cannot happen via the bees system.

Bees do ingest oxalic when trickled in syrup according to some research.

This observation leads to the hypothesis that oxalic acid crystals are collected in great
numbers with the adhesive pads on the mites feet, where they then dissolve within a few hours and
penetrate the body of the varroa via the membranes in the adhesive pads.[/I]

Looks to be the likely way mites are killed.

This amount used in beekeeping practice seems to be too low to reach a systemic toxicity to V. destructor through ingestion. Therefore, we conclude that the mode of action in the colony must be contact poisoning against V. destructor.

Effects of Oxalic Acid on Apis mellifera (Hymenoptera: Apidae)
Eva Rademacher *, Marika Harz and Saskia Schneider
Institute of Biology/Neurobiology, Freie Universität Berlin, Königin-Luise-Str. 28-30, 14195 Berlin, Germany
*
Correspondence: Tel.: +49-30-8385-6537
Academic Editor: Brian T. Forschler
Received: 12 June 2017 / Accepted: 2 August 2017 / Published: 7 August 2017

Conclusions
OAD used to treat varroosis of A. mellifera shows a rapid and consistent distribution in the colony for at least up to 14 days, and high efficacy against the mite, but also lethal and sublethal effects. In practical beekeeping, appropriate use of OAD (one topical application, on average 175 µg/bee) is relatively safe for A. mellifera at the colony level, even when some individuals are lost. However, ingestion leads to high mortality. The reported sublethal effects are highly decreased longevity, a reduction in pH-values in the digestive system and the hemolymph, and an increased responsiveness to water. The shift towards stronger acidity after treatment confirms that damage to the epithelial tissue and organs is likely to be caused by hyperacidity. Pathological repercussions e.g., degeneration of rectal epithelium, malpighian tubules and ventriculus may also occur.
These results indicate a general impairment of the bees after treatment. The treatment in autumn or winter affects primarily long-living winter bees which are essential for winter survival and successful colony development in the spring. Treatment during summer with brood can cause substantial brood damage. Even when treating artificial swarms or nucleus colonies it cannot be certain that damages will not occur due to the extensive exposure to OAD in the colony. Long-term effects such as reduced amount of brood in treated colonies have been reported.
OAD is one of the most important organic acids used for the control of V. destructor. It is indispensable but must be dosed precisely and applied as seldom as possible to prevent sublethal damages which eventually lead to the loss of bees. Long disposition in the bee hive can cause accumulation of the acid and therefore induce further damage.

Full paper here...
http://www.mdpi.com/2075-4450/8/3/84/htm

 

[ShinySideUp]

The last piece, quoted by Hivemaker, might indicate that administration of OA by sublimatioin might be preferable for individual bees as any one bee is less likely to ingest a lethal dose than when using trickling but looking at the hive as one organism then either method seems to be effective (no, I'm not resurrecting the trickling/sublimation discussion).

It has certainly been effective on my hive as the mites are dropping in their thousands now (which concerns me that the load was so high without a large general mite drop before treatment). Strangely, my all-summer-long nuc box is almost free of mites and even after OA trickling, mite drop is in the tens...or less.

 

[charlievictorbravo]

The last piece, quoted by Hivemaker, might indicate that administration of OA by sublimatioin might be preferable for individual bees as any one bee is less likely to ingest a lethal dose than when using trickling but looking at the hive as one organism then either method seems to be effective (no, I'm not resurrecting the trickling/sublimation discussion).

It has certainly been effective on my hive as the mites are dropping in their thousands now (which concerns me that the load was so high without a large general mite drop before treatment). Strangely, my all-summer-long nuc box is almost free of mites and even after OA trickling, mite drop is in the tens...or less.

If they're well behaved and can produce a surplus of honey, then that's the colony to be breeding with.

CVB

 

[ShinySideUp]

If they're well behaved and can produce a surplus of honey, then that's the colony to be breeding with.

CVB

They are quite calm and good with honey and the queen is in her third year next year. SHe will be moved into a full hive in the spring then I will split to get another hive and see if she goes for 2018 -- I'm a softie at heart and putting down a healthy queen goes against the grain even though it's a heartless, stinging insect!

 

[For want of a better word]

If they're well behaved and can produce a surplus of honey, then that's the colony to be breeding with.

CVB

Majority of my Cornish Native Amm do not show high infestation of varroa... perhaps Shiney's bees have interbred with the high level of Amm in the area of the Tamar / Lynher / Inney drone flooded catchment?



Trolls now climbing out from beneath bridges to have a good ol' Winter rumble!!

Nos da

 

[Beefriendly]

As you are constantly "baiting" with provocative posts are you surprised?
If Cornish Amm's were the miracle bees you repeatedly suggest they are ...why isn't the world beating a path to your door?

 

[For want of a better word]

As you are constantly "baiting" with provocative posts are you surprised?
If Cornish Amm's were the miracle bees you repeatedly suggest they are ...why isn't the world beating a path to your door?

Only in Cornwall!.... and possibly into the greater South West

Nadelik Lowen ha blydhen nowydh da

 

[SDM]

:

Only in Cornwall!.... and possibly into the greater South West

Nadelik Lowen ha blydhen nowydh da

Where standards are lower.