Another plethora of neonicotinoid articles today...

[Jon]

tweak one of those estimates and the results change dramatically.

Someone made a similar point on Bee-L recently.
If you lost 5% foragers over and above normal losses over a few days it would be almost unnoticeable - but might make the difference between a colony producing some surplus honey or none at all.
The commercial beekeepers in particular seem to work on very tight margins.
Maybe in a worst case scenario is could be the trigger for collapse over winter.
Bees in the UK certainly manage a surplus foraging on the neonicotinoid treated oil seed rape which suggests that there is no significant loss of foragers occurring.
The default position is that pesticides are not good for bees, some are harmful, some are very dangerous so what percentage loss/damage is acceptable.
And again the ban the neonicotinoid people need to be really careful about getting what they wish for if the replacement/older stuff is going to be worse.

[Neils]

I think you also need to factor in Gavin's point as well, once bees are no longer being exposed to neonicotinoids they metabolise it fairly rapidly. Once, in this case, the OSR finishes, what are they foraging on next? A hypothesis is that larvae may be better than adult bees at metabolising alkaloids generally.

Given that surpluses are stored and concentrated in the form of honey, has anyone actually looked at what level of neonicotinoids are present in honey? Is it greater, the same or less than that found in nectar/pollen?

[Jon]

Certainly any food product would be routinely monitored for pesticide residues.
Didn't some of those studies by Engelsdorp et al and some of Marla Spivak's work look at pesticides found in the hive.
The most prevalent ones were those put there by beekeepers for varroa control.

http://othes.univie.ac.at/9119/

[Neils]

Depends what they're looking for, if they're looking for levels that would be relevant from human consumption then I doubt they're looking at levels that would be relevant to Honey bees.

Would neonicotinoids be found in wax anyway?

[Jon]

I think pesticides of any flavour are more likely to be in the wax than the honey and again there are loads of studies measuring the levels and the effect on developing brood. One good reason for changing old comb I suppose.

This was a good Engelsdorp paper from 2009

This is another about pesticide in comb

[Neils]

The point with neonicotinoids are they're in the nectar to begin with, not being introduced into the hive via any other machanism other than pollen. Is it feasible that they'd "leech" out of the nectar/honey leaving that uncontaminated while the residues are solely in the wax? If its only in the wax does it matter? I thought that they had to be ingested to be effective?

Residues of pesticides effective through contact found in wax would presumably be of more concern.

[Jon]

That second reference I posted mentions how pesticides can move from contaminated comb to fresh comb within the hive. I think once contaminants are in there they will move or be moved about freely.

Pesticide in wax has all sorts of effects on larvae and bee longevity.

[Neils]

Sure, but that's the answer to a different question in some respects. Are neonicotinoids even absorbed into wax in the first place? if they are does that mean that if you analysed Neonicotinoid levels in Nectar being taken into the hive that levels will drop over time as it leeches into wax? If it gets into the wax, does it matter? Presumably for the most part it will be localised in the combs used for storage and what little ends up in and around the brood will be metabolised fairly quickly once exposure ends.

If it's in the honey though, how much of that is consumed on an ongoing basis? i.e. is the fact that they're no longer foraging on treated forage irrelevant because they're still consuming it through contaminated nectar and pollen stored within the hive from earlier?

[gavin]

Guys

Nice to see you busy thinking.

Chris: the neonic half-life work was done in the lab if I remember right, so would not be biased by foragers not returning. I still think that a reaction to pesticides in the field doesn't necessarily mean that there is a problem, just that the organism has been exposed and is now reacting. All organisms react to challenges, and that is what is being reported as a biochemical marker. The bee is reacting to AChE inhibitors by producing more.

On the partitioning and persistence, I've had a look again at the Mullin paper (http://www.plosone.org/article/info%...l.pone.0009754) imidacloprid (like other neonics) was surprisingly rarely found in samples from colonies. 1%, 3% and 0% of wax, pollen and bee samples respectively. That's surprising given the near-ubiquity of the neonics as insecticides. I reckon the reason is that the bees metabolise it.

What about the partitioning to wax? Mean levels in wax, pollen and bees were 0.1 ppb, 3.1 ppb and 0. This implies that it doesn't accumulate in wax but stays in pollen. The lack of detections in bees probably means that they are metabolising it. The selective loss of exposed bees doesn't apply when sub-lethal levels are readily detected.

Honey? They didn't test honey but a local bee farmer has shown me the lab tests on his OSR harvests which are a requirement for his supermarket contracts. Nothing.

Happy to be corrected if you know more.

That study Jon mentioned does have imidacloprid 'on comb' at quite high levels. Not entirely sure how to square that - maybe the bees are using contaminated cooling water in some environments on unused comb which gives these infrequent but high detections?

[Neils]

How much might the method of operation matter? Pyrethoids, for example, I gather work primarily through absorption, Neonics through ingestion. While in neither case that's necessarily exclusive it seems to me reasonable that pyrethoids could be more "willing" to linger in wax. Wasn't that fundamentally the problem with DDT? not much is able to metabolise it and it loves Fat so just keeps on moving up the food chain in greater and greater concentrations.

I think when it comes at the moment to testing in Honey the question still remains are the tests looking for levels of contamination that is harmful to humans or harmful to bees?

Aside from Dr Cresswell I've read about Bees' ability to metabolise Neonicotinoids elsewhere. Someone put it down to their original evolution in Africa where plants commonly have alkaloid compounds in their nectar (apparently Neonicotinoids are alkaloids and with that I've exhausted my knowledge of chemisty/plant biology) compared to, say, here where they commonly don't and suggesting as a result that if one were to look for problems in bees resulting from neonicotinoids that one might be better off looking at bumbles and solitary bees. The obvious downside to that being that aside from a few species of Bumble that they're not kept/raised by us.