I wrote to the author of the Nature paper, what follows is our exchange:

I read with interest your recent paper (Non-cultivated plants present a season-long route).  I thought the methodology was sound and the results notable. However, there has been criticism of it by others. How would you respond to these comments?

> every sample contained DEET.  I haven't seen DEET (mosquito repellant) in the samples of other investigators. I'd suspect that the Nature paper field crew wasn't wearing disposable gloves when handling pollen samples, and that they contaminated every sample.

> the biggest issue is that this paper is based on the results from 2 colonies at 3 small 3.7 acre field sites, in one county in Indiana. This this study is apparently considered adequate for characterizing bee exposure to corn-soybean agro-ecosystems.

His reply:

Peter,

Thanks for your note and for forwarding the comments. I am always happy to hear reaction of any kind to the work. I have heard the DEET contamination comment several times since the work was published. It is most surprising that the commenters think we would not have thought of that obvious source of contamination. However, all samples were collected and handled by the same individual (me), always with disposable gloves, and I never wore any insect repellent. In fact, I rarely wear repellent at any time. During the lab work, we were similarly careful to always wear gloves during handling. I too initially doubted that spike and we had it re-confirmed multiple times by the analytical chemist who did the analyses. We speculate on its origin in the manuscript but it is a bit of a puzzle.  

On the second point - we do not assert that this study characterizes exposure in all corn-soybean systems. I am not aware that anybody has else stated that it is adequate for that purpose. We take pains in the manuscript to point out that this is a small study, low sample size etc. But it is a start, in that it is the first work to characterize both the pollen foraging habits of the bees (which may prove to be the most interesting/useful piece of the paper, long-term) and the pesticide residues in the monocultures that typify much of the country. More samples/sites are difficult without more resources (i.e. money); this is always desirable. And we did not do any assessments of honey bee health, which would be a key next step for interpreting what this all means at the population level. 

Feel free to send these comments on to any who you think would be interested in them. Thanks again,

CK

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