Hi all
Those who don’t know the history of the varroa mite problem, maybe don’t realize that most of the important work was done decades ago.
> Since 1974, research on chemical controls has been done at 22 institutes in the USSR with over 100 chemicals tested … In 1978, KeIthane® (Dicofol) was used ... In 1979 formic acid was used as a fumigant … Each chemical at the time was supposed to be the most thorough control available, yet the number of infested colonies increased each year … The Japanese and the Russians have determined that hot air blown into the hive will dislodge many mites from the bees
DE JONG, MORSE & EICKWORT (1982) MITE PESTS OF HONEY BEES
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Insofar as the mode of action of varroacides goes, some information is of limited usefulness such as
> Formic acid is inhibiting electron transport in the mitochondria binding of cytochromec oxidase in mites and may produce a neuroexcitatory effect on arthropod neurons. Formic acid can reduce worker longevity and harming brood survival.The mode of action of oxalic acid against Varroa is unknown.
> Amitraz is a formamidine pesticide. The mode of action of formamidine pesticides such in insects is believed to be the toxic effects on a G protein-coupled receptor for a neuromodulator octopamine, working as octopaminergic agonists. High levels of octopamine in the honey bee brain are associated with increased foraging behavior. … the acute toxicity of this compound was shown in larvae where it increases apoptotic cell death in the midgut
And these are the ones that no one wants to hear:
> Two monoterpenoid components of plant- derived essential oils, thymol and menthol, are used for control of Varroa and tracheal mites. They were found to be among the most toxic of all terpenoids tested when applied to honey bees as a fumigant
> Boncristiani et al. found that thymol, coumaphos and formic acid are able to alter detoxification gene expression pathways, components of the immune system responsible for cellular response and developmental genes. This study indicates that these acaricides could significantly influence the health of individual honey bees and entire colonies
Glavan, G., & Bozic, J. (2013). The synergy of xenobiotics in honey bee Apis mellifera: mechanisms and effects. Acta Biologica Slovenica, 56(1).
Boncristiani, H., Underwood, R., Schwarz, R., Evans, J.D., Pettis, J., vanEngelsdorp, D., (2012). Direct effect of acaricides on pathogen loads and gene expression levels in honey bees Apis mellifera. Journal of Insect Physiology, 58 (5), 613–620.
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