Hi Ghislain, Re the Suchail study that you cited, here are some notes that I wrote: Suchail fed imidacloprid and some of its metabolites to bees in syrup for 10 days (chronic exposure). Her conclusions were stunningly surprising (her term): her results indicated that with chronic exposure, imidacloprid and its metabolites were toxic to bees at levels 60-100,000 times lower than that reported by others in acute intoxication studies! Those figures proved to be anomalies, though, and have not been replicated by other researchers (Schmuck 2004). So we must ask ourselves, how could Suchail have found a level of toxicity so far out of line compared to the results of other researchers? Unfortunately, the paper is not readily available on the web, so despite being unquestioningly referred to by nearly every anti-neonic paper and blog, I suspect that many have actually only read the abstract. I’ve personally spent some time going over the paper, and completely agree with the authors that their results were not only surprising, but completely implausible! So let’s look at her actual methodology, which brings up a few questions: 1. To start with, Suchail used older bees rather than younger bees from the brood combs (these bees would not only be nearer to natural death, but also lacking in protein reserves). 2. She also made the questionable decision to take all the bees for all “replicates” from only one colony, instead replicating the experiments with bees from multiple colonies, which may differ in health and susceptibility to the toxin. 3. She apparently did not check the bees for nosema or other infections. 4. She then stressed the bees by both treating them with CO2 (which can shorten lifespan) and then holding during the trials in an incubator at a relatively cool temperature (dropping as low as 74°F) which can increase both bee stress and pesticide toxicity. 5. Suchail did not show the mortality curves for the control (untreated) bees, although she says that “mortality of the control did not exceed 15%” over the 10-day trial (I typically see close to zero mortality in 10 days). The control curve should have been shown. 6. In order to make sure that a toxicological experiment is actually measuring a “real” effect of the treatment, one often adds a “positive control” with a known toxin (usu. Dimethoate). Since Suchail didn’t do this, it is difficult to draw conclusions from her data whether there was any actual toxic effect from any of her treatments (see below)! 7. I’m then not sure about her “replications,” especially since she states that there were no deviations from the means, inferring that exactly the same number of bees died each day in all three cages in each treatment group. It’s rather incredulous to see zero deviation in trials run in triplicate! 8. Suchail also added an inexcusable variable—dimethyl sulfoxide (DMSO). DMSO is a nontoxic solvent that is used to penetrate biological membranes. It is used as a drug delivery enhancer to carry compounds through skin or other membranes without damaging them. It increases the rate of absorption of pesticides through the skin to the extent that a toxicolologist that I questioned told me, “In our formulation work, we stay away from using DMSO due to its high adjuvancy and penetration enhancement which is a danger to the worker or researcher. If you are not careful to protect yourself, you would end up bringing the toxicant into your body through dermal penetration.” Note that a study by Suchail in 2004, she found that imidacloprid is not normally well absorbed through the gut wall. DMSO is not used in field applications of imidacloprid, so for Suchail to add it to the test syrup seriously undermines the relevance of her study in reflecting the normal absorption of the pesticide. This fact alone is enough to make a case for discounting the results of Suchail’s experiment. -- Randy Oliver Grass Valley, CA www.ScientificBeekeeping.com *********************************************** The BEE-L mailing list is powered by L-Soft's renowned LISTSERV(R) list management software. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html Guidelines for posting to BEE-L can be found at: http://honeybeeworld.com/bee-l/guidelines.htm