Usually when we want to get rid of an insect or other arthropod we spray it with something nasty. And that is indeed what beekeepers do to kill varroa destructor, a mite that infects beehives and contributes to Colony Collapse Disorder (CCD), a sudden bee die-off.

But aren’t we forgetting something fundamental here? Insecticides kill insects – bees are insects – insecticides kill bees? One of such, imidacloprid, widely used by farmers, is even suspected of being a main cause of CCD.

But of course not all poisons are equal and not all animals under one inch length share the same metabolism. This is why clever biochemists have designed a special class of pesticides, called acaricides, intended to single out the subclass of ticks and mites, or acari.

Pesticides & ecology: poor track record

But such poison brewers have something of a history to mix up theory and practice. For instance the Swiss chemist Paul Müller in 1948 won the Nobel Prize in Physiology or Medicine for discovering the pesticide DDT ‘was effective as a contact poison against several arthropods’ – not because it was almost equally effective in wiping out stork or bald eagle populations, or anything else feathered high up in the food chain.

So two decades after introduction of the compounds a group of entomologists of the University of Illinois thought it may be a good thing to check if really the two acaricides [The pyrethroid tau-fluvalinate and the organophosphate coumaphos] that beekeepers use to kill the bee-killing mites, don’t accidentally have something to do with CCD themselves.

What doesn’t kill you can make you weaker

In their PNAS publication [latest edition print, July 20 | online edition, June 27] they conclude at first sight we’re fortunate. Bees, like humans, have a wide range of detoxifying P450 enzymes. Some of these [CYP9Q1, CYP9Q2, and CYP9Q3] proved effective at metabolising both pesticides.

Being ‘able to metabolise’ something does not make that substance healthy. Human livers metabolise alcohol too – but at a cost. And general bee health may be an actual CCD concern.

Moreover, as the enzymes are needed to neutralise both toxins, using a pesticide cocktail to combat varroa destructor mites could be unwise. Two non-lethal doses could add up to one overdose.

Healthy bees more likely to survive insecticide dose

Besides, the bees’ ability to produce P450 enzymes can vary, the researchers state:

“Induction of CYP9Q2 and CYP9Q3 transcripts by honey extracts suggested that diet-derived phytochemicals may be natural substrates and heterologous expression of CYP9Q3 confirmed activity against quercetin, a flavonoid ubiquitous in honey. Up-regulation by honey constituents suggests that diet may influence the ability of honey bees to detoxify pesticides.”

So perhaps their dietary intake of micronutrients not only affects the bees’ defence against pests, but also against pesticides.

Message for the beekeepers: if really you have to spray the hyves with poison, don’t save expenses on classic damage control – and buy your bees a nice, big mixed bouquet.

© Rolf Schuttenhelm | www.bitsofscience.org