Varroa Mite and Neonicotinoid Pesticides
Varroa mite is one of the biggest threats to honey bee colonies. In the UK, it was first discovered in 1992. Exposure to this pest causes viruses and diseases to be transmitted to honey bees. But could it be that neonicotinoid pesticides impair the ability of honey bees to deal effectively with Varroa mite? Treatments against Varroa mite are increasingly found to be ineffective, and it is often said that the mites may have developed a resistance to the chemical treatments available. However, a key natural defence for honey bees against Varroa is for the bees to become “hygienic” – this means, the bees are able to groom and remove the mites from larvae and their bodies. In fact, there are currently efforts to breed “Hygienic bees” that are more likely to engage in this crucial grooming behaviour. Watch how the honey bee deals with the Varroa mite once it has been removed on this video
here (opens new window).
But, given the mode of action of neonicotinoids, is it surprising if these insecticides hinder the ability of bees to develop this grooming ability?
"What is Premise 200SC plus Nature? Low doses of imidacloprid such as the edge of the Treated Zone, disoriented the termites and caused them to cease their natural grooming behaviour. Grooming is important for termites to protect them against pathogenic soil fungi. When termites stop grooming, the naturally occurring fungi in the soil attack and kill the termites. Imidacloprid makes fungi 10,000 times more dangerous to termites. Nature assists imidacloprid in giving unsurpassed control. This control is called Premise 200SC plus Nature." Could it be, then, that neonicotinoids interfere with grooming behaviour in honey bees, making them more likely to succumb to Varroa mites and the diseases they carry? As stated, although this leaflet is particularly concerned with termites and not bees, nevertheless, termites, like bees, are social insects. Imidacloprid is a neonicotinoid, and it is used on farmland, as well as being available for use in gardening and lawn care products. In view of this information, I would like to know whether regulatory approval bodies (such as DEFRA or the CRD in the UK), considered the impact of these pesticides on crucial natural insect behaviours such as these. Have they even requested data from Bayer Cropscience investigating the impact on grooming behaviour in honey bees? Did Bayer submit such data, and if so, what steps are the regulatory bodies taking to ensure the data is independently scrutinised? Are they requesting visibility of independent data? Further evidence of the effects of neonicotinoids on grooming behaviour has also been witnessed in beetles, including having an impact on their larvae. This published study, titled Synergism of imidacloprid and entomopathogenic nematodes against white grubs: the mechanism; by Albrecht M. Koppenhöfer et al in 2000, states:
"Brushing (legs or mouth parts swept across body)……and chewing ….occurred significantly more often in grubs not treated with imidacloprid in the presence of nematodes and this response was reduced by 42--70% after imidacloprid treatment." It seems to me that unless it is proven that neonicotinoids do not impair crucial grooming behaviour in honey bees and non-target insects, then this is further justification for a precautionary suspension, in line with the request from Invertebrates charity, Buglife. It has also been demonstrated that the interaction between the microsporidia Nosema and a neonicotinoid (imidacloprid), significantly weakened honeybees. This study by Alaux et al was published in Environmental Microbiology 2009: Interactions between Nosema microspores and a neonicotinoid weaken honeybees (Apis mellifera) UPDATE In a feature in the Independent newspaper, it is reported that in response to the question of whether Bayer had tested for the effects of neonicotinoids on grooming in honey bees, the reply was 'no': Quote from the newspaper: "Dr Julian Little, Bayer's UK spokesman, said: "We do a lot of tests of the effects of insecticides on bees, and impairment of grooming has never shown up."  Go back from Varroa Mite and Neonicotinoid Pesticides to Home page
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