# Assessment of Chronic Sublethal Effects of Imidacloprid on Honey Bee Colony Health



## AmericasBeekeeper (Jan 24, 2010)

Assessment of Chronic Sublethal Effects of Imidacloprid on Honey Bee Colony Health
Here we present results of a three-year study to determine the fate of imidacloprid residues in hive matrices and to assess chronic sublethal effects on whole honey bee colonies fed supplemental pollen diet containing imidacloprid at 5, 20 and 100 μg/kg over multiple brood cycles. Various endpoints of colony performance and foraging behavior were measured during and after exposure, including winter survival. Imidacloprid residues became diluted or non-detectable within colonies due to the processing of beebread and honey and the rapid metabolism of the chemical. Imidacloprid exposure doses up to 100 μg/kg had no significant effects on foraging activity or other colony performance indicators during and shortly after exposure. Diseases and pest species did not affect colony health but infestations of Varroa mites were significantly higher in exposed colonies. Honey stores indicated that exposed colonies may have avoided the contaminated food. Imidacloprid dose effects was delayed later in the summer, when colonies exposed to 20 and 100 μg/kg experienced higher rates of queen failure and broodless periods, which led to weaker colonies going into the winter. Pooled over two years, winter survival of colonies averaged 85.7, 72.4, 61.2 and 59.2% in the control, 5, 20 and 100 μg/kg treatment groups, respectively. Analysis of colony survival data showed a significant dose effect, and all contrast tests comparing survival between control and treatment groups were significant, except for colonies exposed to 5 μg/kg. Given the weight of evidence, chronic exposure to imidacloprid at the higher range of field doses (20 to 100 μg/kg) in pollen of certain treated crops could cause negative impacts on honey bee colony health and reduced overwintering success, but the most likely encountered high range of field doses relevant for seed-treated crops (5 μg/kg) had negligible effects on colony health and are unlikely a sole cause of colony declines.

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0118748


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## AstroBee (Jan 3, 2003)

Interesting study. Seems that the takeaway may suggest that seed coatings may not be as detrimental as previous thought. However, when concentrations are higher, e.g, direct spray, a much different situation may result, with particular impact on queens.


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## AmericasBeekeeper (Jan 24, 2010)

That is why the farmers, seed companies and the EPA want the products on the seed, targeting the problem directly and not drencing everything around the plants.


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## AmericasBeekeeper (Jan 24, 2010)

Correction: Assessment of Chronic Sublethal Effects of Imidacloprid on Honey Bee Colony Health
In the Results section, there is an error in the third sentence of the first paragraph where the units of imidacloprid are incorrectly stated in mg instead of μg. The correct sentence is: Based on total consumption over 12 weeks, each colony of the 5, 20 and 100 μg/kg treatment groups was exposed to an average cumulative dose of 16.6, 63.7 and 322.6 μg of imidacloprid, respectively.
Reference
1.	1. Dively GP, Embrey MS, Kamel A, Hawthorne DJ, Pettis JS (2015) Assessment of Chronic Sublethal Effects of Imidacloprid on Honey Bee Colony Health. PLoS ONE 10(3): e0118748. doi:10.1371/journal.pone.0118748. pmid:25786127 

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0126043


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## Michael Bush (Aug 2, 2002)

>That is why the farmers, seed companies and the EPA want the products on the seed, targeting the problem directly and not drencing everything around the plants.

So we can permeate the entire plant and we get to eat it...


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## AmericasBeekeeper (Jan 24, 2010)

To do that they would have to sell neonicotinoids in more than 70 of the 155 plus countries. It would also require an mis-understanding that neonics are absorbed by the plant and target sap sucking insects unlike all other insecticides. But we get to rediscover broad spectrum insecticides when neonics are banned.


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