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Posted 17 July 09

For those interested, back in March this year, The Honey Bee Advisory Committee met with Bayer Chemical to discuss, among other things, issues they had with some of the chemicals Bayer is selling. The report of the meeting was published on Bee Culture's CATCH THE BUZZ, and in Bee Culture magazine. Bayer has responded to the report submitted by the beekeepers, and after review, EPA has posted it on their site ... you can download the original .pdf file here

I have pasted Bayer's response below together with a report by Dr. Daniel Mayer - a scientist who appears to have been the independent investigator employed by the North Dakota bee-farmers to present their case against Bayer in court. It is a very good summation of all the evidence and deserves a wider distribution- even though it is 3 years old. If you have not read these documents yet, perhaps you should. They are enlightening.

Response to National Honey Bee Advisory Board Letter on Imidacloprid Registration Review

Dear National Honey Bee Advisory Board:

Bayer CropScience read with interest your public comment letter dated March 17, 2009 to the EPA concerning the Agency’s registration review of imidacloprid. We fully recognize the value pollinators bring to US agriculture and the dedication of those in the business of beekeeping. We empathize with those beekeepers that have experienced extensive colony losses in recent years and support research efforts to identify the underlying causes of this syndrome. However, reliable research to date does not support the contention that imidacloprid or other agricultural pesticides have caused these losses and we feel compelled to comment on several points that you raised.

You state that “Beekeepers from around the United States, and around the world, have had persistent problems associated with the use of the systemic pesticide imidacloprid”. This is simply not true. Commercial use of imidacloprid began in the US in 1994. Coinciding with the introduction of the sweet potato whitefly and extreme resistance development in Colorado potato beetle to other chemicals, imidacloprid-based products quickly became a market leader in major crops including cotton, potatoes, and a broad array of vegetables, many of which have been pollinated by bee colonies supplied by members of your organization for years. These introductions of imidacloprid-based products such as Admire® and Provado® were NOT followed by any claims of harm to bee colonies by beekeepers in the US. In fact, imidacloprid had been in widespread use in US agriculture for more than a decade before the syndrome now called “colony collapse disorder” began being reported.

The first claim in the US that imidacloprid had harmed bee colonies was the case in North Dakota that was brought to the attention of Bayer in 2001. A group of beekeepers claimed that imidacloprid used as a canola seed treatment harmed bees which foraged on this crop. You describe this case, which formed the basis of the Bauer et al. vs. Bayer Corporation lawsuit, in your letter to EPA as “the largest incident” of “major incidents [that] have been reported by beekeepers linked to imidacloprid.” It is surprising that you cite this case as an imidacloprid incident since the allegations of Bauer et al. were not proven. This is not just Bayer’s opinion. The United States District Court for the Middle District of Pennsylvania, after considering the evidence presented, granted Bayer’s Motion to Dismiss this case in June, 2008. The analytical data you cite in your letter were discredited based on the fact the analytical method used to generate them was not scientifically sound. The original chemical analysis by ADPEN Laboratories, Inc. which reported high levels of imidacloprid in wax and honey samples from plaintiff’s hives also showed high levels of imidacloprid in control samples that were assumed to be chemical free. This was a red flag that the analytical work was flawed, and indeed upon examining it further, it was determined that the analytical method that was used was inappropriate and unreliable for analysis of imidacloprid. ADPEN repeated their analysis of plaintiff’s samples using a proven and validated analytical method and found concentrations ranging from <0.5 to 3.2 ppb. These are levels consistent with previous research and do not support the conclusion that plaintiff’s bees were harmed in any way by imidacloprid.

The remaining “beekeeper incidents” you list in you letter are anecdotal with no definitive, reliable or scientific evidence linking the colony dwindling or losses that were observed to exposure to imidacloprid. There are many other possible explanations for these losses. It is not clear to what extent these have been considered.

Recent research (for example, Cox-Foster et al., 2007, Science 318:283-287; Higes et al., Environmental Microbiology Reports 1(2):110-113; 2009) has shown that CCD-type losses are associated strongly with presence of pathogens such as Nosema ceranae and various viruses. Field observations also suggest it is caused by an infectious agent and not a chemical. In the February 2009 issue of Bee Culture, Debnam et al. wrote: “Normally when a strong colony is combined with a collapsed one from the same apiary it also collapses. Once the symptoms start they seem to affect most colonies in that apiary. We’ve seen CCD travel like a wave through large holding yards.”

There is no scientific evidence that CCD losses are associated with imidacloprid exposure. Researchers from Pennsylvania State University (Dr. Chris Mullin, et al.) sampled wax and pollen samples from hives of commercial beekeepers that were experiencing CCD losses. Data presented by this team to the Entomological Society of America in December 2007 showed no correlation between colony losses and presence of imidacloprid residues. In fact, imidacloprid was detected in <10% of the samples reported in this study. An article by this research team entitled “What have pesticides got to do with it?” published in June 2008 issue of American Bee Journal doesn’t even mention imidacloprid at all! According to this article, the chemicals of greatest concern are those applied by beekeepers themselves – miticides targeting Varroa destructor, an introduced parasite of the honey bee.

All chemicals are toxic to bees when the dose is high enough and all chemicals are safe to bees when the dose is low enough. In the case of imidacloprid, chronic testing with bee colonies has established that no adverse effects are to be expected when the concentration in pollen and/or nectar that bees are exposed to is <20 ppb. Field studies have shown that when imidacloprid is applied per label directions, concentrations in pollen and nectar of agricultural crops are almost always below this no-adverse-effect concentration. These field studies have NOT shown any harm to bee colonies when imidacloprid is applied to agricultural crops per label directions. This includes studies performed by university and government scientists in Argentina, Canada, France, Germany, the United Kingdom, and the United States. No pesticide has been more thoroughly tested for safety to honey bees than imidacloprid.

Your letter advocates suspending registration of imidacloprid in the US. Suspending imidacloprid and/or other neonicotinoid insecticides in the US will cause major hardship for farmers (not to mention consumers of fresh fruits and vegetables) and almost certainly do nothing to improve the health of US bee colonies. In France, no improvement in bee health occurred as a result of the suspension of Gaucho®. Recent reports of the French Food Safety Agency (AFFSA) have concluded that Gaucho® played little if any role in the massive bee colony losses that occurred in France during the late 1990’s and early 2000’s. These reports conclude that the main factors causing these losses were varroa mites, pathogens (including viruses and Nosema ceranae), nutritional deficiencies, and beekeeper use of unapproved miticides. Bee health monitoring studies in Germany and Canada have also indicated biological factors, rather than pesticides, are the main factors causing colony losses.

Contrary to your intent, if enacted, the suspension of imidacloprid registrations in the US is likely to have a negative impact on beekeepers because growers will compensate for the loss of an effective systemic control of insects by increasing the number of broadcast spray applications of other insecticides. One seed or soil application of a systemic insecticide typically replaces the need for three or more foliar spray applications. Insecticide spray applications have a much greater potential to cause bee kills and subsequent hive damage. They also have a greater likelihood of contaminating nearby terrestrial and aquatic habitats via spray drift and storm water runoff.

Bayer CropScience welcomes a dialogue with the NHBAB and other stakeholders who have an interest in ensuring risks to honey bees and other pollinators are appropriately considered when pesticide products are developed and undergo regulatory review. We hope you agree that the best available science should be applied in order to reach this goal. We are confident that when the best available science is applied, the conclusion will be that the use of imidacloprid per label directions does not cause an unreasonable risk to honey bee colonies.

Sincerely yours,
David L. Fischer, Ph.D.
Director, Ecotoxicology
US Global Research and Development


BUZZ ME Daniel F. Mayer, Ph.D. 743 Sheafman Creek Road Hamilton, MT 59840 (406) 961-1577

By Daniel F. Mayer, Ph.D.

31 July 2006

Bayer was Negligent Concerning Imidacloprid and Honey Bees

Bayer was negligent concerning imidacloprid residues in different soil classes Bayer did not adequately determine the persistent of imidacloprid in soil in relation to environmental conditions. Bayer now states imidacloprid persists in the soil for more than one year. In their early research it appears that Bayer thought imidacloprid would persist in the soil for only one growing season and have no biological effect the following year (case of CPB).

The half-life of imidacloprid ranges from 39 days to more than in year in sandy, loam soil and its primary metabolite, 6-chlornicitonic acid, may also be highly toxic.

Bayer was negligent concerning data submitted to EPA for registration of Gaucho

Under the provision of FIFRA, the EPA approves and authorizes the marketing of a pesticide following an array of tests performed by or on behalf of the manufacturer. New insecticides are invariably evaluated for their toxicity to honey bees, but this evaluation is almost always limited to measures of the 24-hour LD50 (the dose that results in the death of half of the subjects to which it is applied in 24 hours). This was the only test EPA required of Bayer by the EPA before approval of imidacloprid. Based on this data The LD50 is determined orally or by topical drop to determine the direct toxicity. Imidacloprid was determined to be highly toxic to honey bees. EPA imposed certain restrictions on the sprayable forms of imidacloprid such as application timing, rate and restricted crop use to protect honey bees. However, they did not impose any restrictions on the use of imidacloprid as a seed treatment or for soil applications.

Gaucho (imidacloprid) is used as a seed treatment at the time of planting and the imidacloprid moves systemically through the plant during the growing season killing insects. Based on its application method the EPA did not require Bayer to submit any data on the bee hazard of Gaucho to honey bees. In the case of Gaucho as a seed treatment they did not ask Bayer for any bee toxicity data due to the method of application, especially when Bayer assured EPA, without supplying any scientific data, that there were no problems with bees because of the method of application.

The EPA did not require Bayer to submit data from any inhalation, neurotoxicity, oncogenicity, teratogenecity, reproduction or mutagenecity studies on honey bees. And, in fact, Bayer did not conduct any of these types of studies with imidacloprid and honey bees.

Bayer should have conducted tests on honey bees with Gaucho since they knew that imidacloprid was present in plant flowers for most of the growing season and therefore honey bees were exposed to imidac1oprid.

Bayer was negligent concerning field test on the effects of Gaucho on honey bees.

Bayer did not conduct a large scale field test to determine the effects of Gaucho treatments on honey bees. Bayer conducted some small scale field and tunnel tests with Gaucho. However, data collected in these type tests only rarely provides data or information on what happens when a product is marketed widely and used on large acreages.

Honey bees forage about one mile in all directions. The following is a brief description of a definitive field test on the effects of Gaucho on honey bees. Forty colonies would be placed in the centre of an area where Gaucho treated canola was planted in all fields or nearly all fields in all directions within one mile from the test colonies. This would assure that honey bees forage on imidacloprid contaminated flowers. Biological and environmental data would be collected from the test and control colonies weekly and residue analyses for imidacloprid conducted on adult bees, larvae, honey, wax nectar, plants, soil, etc. The test would be conducted for two years and the fields would be replanted with Gaucho treated canola in the second growing season. This is what happened in the real world in France, North Dakota and other places where beekeepers suffered losses from impidacloprid. Honey bees were exposed to large acreages of imidacloprid treated crops and thus exposed to higher levels of imidac1oprid.

Bayer was negligent concerning imidacloprid residues found in wax from combs and honey and failed to evaluate the residues for toxic effects to honey bees

Bayer should have tested, both chemically and biologically, for imidacloprid residues in wax from combs and from honey. Tests should have been conducted using supers that had been exposed to Gaucho treated crops for several years. Chemists consider wax to be a difficult matrix to work with, however, there are a number of analytical laboratories that can and do conduct residue tests for insecticides found in wax. Also, wax is often a "sink" for pesticides.

Bayer was negligent concerning the effects of moisture on the systemic action of imidacloprid

Bayer did not conduct any tests on the uptake of imidacloprid into plants in relation to irrigation and/or rainfall and the resulting toxic effects on honey bees. For some systemic insecticides, the insecticide moves into the plant at a higher rate when the crop is irrigated. For example, in alfalfa seed fields treated at planting with aldicarb the aldicarb became less biologically active and failed to control insect pests when the fields began to dry up. Then during the middle of the growing season when the fields were irrigated aldicarb again moved up and into the plants killing Iygus bugs.

Bayer was negligent concerning the effects on honey bees of multiple applications of Gaucho to the same field for a number of years

Bayer states that more than one application of Gaucho or an application of Gaucho the following year does not lead to higher residues in the plant even though there are higher residues in the soil. They state that the plant reaches maximum concentration from the first application of Gaucho. This is difficult to believe. They have no scientific data to validate this be faulty, convoluted statement.

Bayer was negligent concerning application rates of Gaucho and failed to consider the toxic effects to honey bees

Almost all substances, including insecticides are dose dependent. In general, higher doses have more biologically activity eventually causing death of the organism while lower doses result in sublethal effects. The effects on the insect are rate dependent.

It is not clear how Bayer determined rates for Gaucho. Growers and insecticide manufactures prefer a systemic insecticide that provides pest insect control for the entire growing season. The field is planted and insect control accomplished with one pass through the field. This is one of the major reasons growers prefer planting seed treated with a systemic insecticide even though other foliar applied insecticides are available. The fact that a systemic insecticide provides season long pest control is a major marketing and selling tool for the manufacture.

Therefore, Bayer chose to use rates of Gaucho that provided season long control for a number of insect pests. There needed to be sufficient imidacloprid present in the flowers during the flowering stage of canola to provide suppression of second generation lygus bugs and cabbage seedpod weevil. Thus Bayer knew imidacloprid was in the flowers and also knew honey bees foraged these flowers for food and were exposed to toxic residues of imidacloprid. Bayer makes the following statement concerning canola, "For suppression of Lygus bugs, including Lygus spp., in their second generation and cabbage Seedpod Weevil larvae, including, including Ceutorhynchus assimilis, apply 15.36 to 25.6 fl. oz per hundredweight of seed".

Bayer could have chosen to use lower rates of Gaucho. Lower rates would have controlled early season insect pests but not provided season long insect pest control. Bayer would have lost a major marketing tool. However, lower rates would have ensured that honey bees were not exposed to or harmed by imidacloprid when they foraged on the flowers.

Bayer could have chosen to restrict Gaucho applications to reduce the harmful effects of imidacloprid on honeybees. For example, they could have allowed Gaucho to be applied to a field only every other year. This would have led to reduced imidacloprid residues in the soil and less harm to honey bees.

Bayer was negligent concerning the No Observed Effect Concentration (NOEC)

The No Observed Effect Concentration (NOEC) is a rather recent hypothesis in the honey bee/pesticide scientific community. Bayer is a leader in promoting the NOEC assumption. There is no scientific basis validating that the NOEC truly means that an insecticide is not harming bees.

The NOEC for imidacloprid on honey bees has been lowered as more research has been completed. The following table indicates that the Bayer tests were faulty and/or data was extrapolated. The NOEC level accepted by Bayer scientists remains at 20 ppb

Researcher NOEC for honey bees
1997 Bayer 5,000 ppb
1998 Bayer 100 ppb
2000 Sclunidt, Bayer 20ppb
1998 Colin & Bonmatin, INRA, France 6ppb
2000 Pham Delegue 4ppb
2000 Colin & Bonmatin, INRA, France 1-3 ppb

Many of the tests conducted by Bayer showed the treated colonies preformed better than the control which in itself is quite unusual. It also raises the question of how does this type data fit into their tremble dance pesticides avoidance scheme which makes honey bees avoid imidacloprid treated flowers.

Bayer maintains that any losses that beekeepers suffer are due to poor beekeeping, mites or other diseases and not because of imidacloprid.

Beekeepers Problems and Loss of Bees from Imidacloprid


In 1997, French beekeepers, having complained for some years about the massive loss of bees and colonies during the sunflower bloom period and about the reduced honey production, made the connection between their losses and the use of Gaucho as a seed treatment. Since then the French have conducted further research of the effect of low levels of imidacloprid on honey bees.

The following results are from French research since 1998 on the effect of low amounts (4 to 10 ppb) of imidacloprid on honey bees. Imidacloprid has a negative effect on length of a bee visit to a contaminated source, consumption, number of visits to a contaminated source, behaviour, ability to recognize relatives, food intake, and olfactory recognition, number of foragers, learning and mortality.

Prince Edward Island

Bees belonging to beekeepers on Prince Edward Island have been exposed to acres of imidacloprid treated crops since 1997. The beekeepers are convinced that the increased use of imidacloprid has caused their increased bee losses. Potato seed pieces were treated with Gaucho and planted and harvested at the end of the growing season. The next year the fields were planted into canola and the beekeepers suffered losses from the residues of imidacloprid in the canola. This has been going on for some time as crops are rotated from field to field.

North Dakota, Texas, Nebraska

Chris Charles and Mitchell Charles are migratory beekeepers based in North Dakota. They have around 8,000 colonies and work closely with another brother who has about 3,000 colonies based in Nebraska. In their operations for honey production they generally place 40 to 48 (6 per pallet) colonies at one location (apiary). They use queen excluders and over winter the most of the colonies in one box in Texas.

In 1999, they began suffering unexplained bee losses of up to 60% of their colonies. There were more "dead outs" and queen loss than normal during the honey production season and winter loss jumped from around 10% to around 50%. In 2001, Mitchell noticed that the cause of these bee losses was in the comb. When they put old comb from the pervious years on top of thriving nucleus colonies in Nebraska they watched the adult bees come tumbling out of the hive, twitching on the ground and dying. These are typical symptoms of bee poisoning from insecticides.

They then sent samples of the comb to the United States Department of Agriculture (USDA) Honey Bee Group at Weslaco, TX. The USDA laboratory conducted some preliminary analytical tests for residues of pesticides but found nothing. The USDA laboratory then referred the Charles to ADPEN Laboratories, INC., a certified chemical analytical laboratory in Jackson, FL.

Henry Graham, Biological Research Technician, from the Honey Bee Group at Weslaco sent six samples of North Dakota bees and bee comb that belonged to the Charles to ADPEN. He asked ADPEN to run an analysis on the material for the insecticides, imidacloprid, carbofuran and dichlorvos.

APDEN analyzed the material for, imidacloprid, carbofuran, dichlorvos and coumaphos. They found residues of imidacloprid in all of the samples. The levels of imidacloprid found ranged from 22 to 671 ppb. These levels are much higher than the LD50 and are certainly killing honey bees and causing sub lethal effects.

The LD50 is the amount of a pesticide that kills 50% of the test population. Using the topical drop method we found the LD50 for imidacloprid for honey bees was 0.04 ug/bee. Depending on method and laboratory, others have reported slightly different LD50 values for imidacloprid and honey bees. Bayer reported in their in-house publication that the oral LD50 was between 41 and 81 ng/bee and the topical LD50 was between 49 and 102 nglbee for imidacloprid .. These values are higher than those reported by others. Some exceptional work in France showed the oral LD50 was 5 ng/bee and the topical LD50 was 14 to 24 ng/bee. However, it is important to point out that in all the LD50 studies conducted, including the work done by Bayer, the LD50 for imidacloprid was very low. The metabolites of imidacloprid are also toxic to honeybees and have sublethal effects on honey bees. There is no dispute that imidacloprid is one of the more toxic contact insecticides for honey bees. And, there is no dispute that imidacloprid at very low ppb has a sublethal negative effect on honey bees.

In mid-July of2003 I met with Chris and Mitch Charles at Carrington, North Dakota. I discussed the honey bee/imidacloprid situation with them. Gaucho was first used in the area in 1995 and a lot was used through 2002. Because of the negative actions of Bayer the Charles brothers were unable to learn the extent of Gaucho use in 2003.

The sequence of events leading to the losses of bees, colonies and honey production is as follows. Canola seed treated with Gaucho is planted and the systemic insecticide imidacloprid moves up the plant and is present in the flowers of canola. Honey bees foraging on the contaminated flowers for nectar and pollen pick up the imidacloprid and take it back to the hive. The nectar is converted to honey. Both the honey and the pollen are stored in the wax combs in the honey supers. Imidacloprid moves from the honey and pollen into the wax. The imidacloprid residues build up in the wax and after two years of field use there is sufficient imidacloprid in the wax to cause bees to behave erratically and die. The colony does not become strong enough to produce any surplus honey and often the whole colony dies. The beekeepers were trying to use uncontaminated foundation in an attempt to reduce losses. But, this mitigation method is very expensive, time consuming and not practical on a large scale.

On July 18, 2003, I investigated the area and examined honey bee colonies in 17 different apiaries. I personally know that many of the canola fields in the Carrington area of North Dakota were planted with seed treated with Gaucho. I personally observed the effects of imidacloprid on honey bee colonies as per the following observations.

  1. Colonies that had been supered with imidacloprid contaminated supers had 300-600 fresh dead adult honey bees in front of each colony and many older dead dried bees underneath the fresh dead bees.
  2. Colonies that had been supered with uncontaminated supers had 5 to 10 dead fresh adult honey bees in front of each colony with only a few older dead dried bees underneath the fresh dead bees.
  3. The bees in colonies that had been supered with imidacloprid contaminated supers appeared disorientated and adult bees were crawling and twitching in front of the colony. These symptoms are typical of bees being killed by an insecticide.
  4. The bees in colonies that had been supered with uncontaminated supers appeared normal.
  5. In colonies that had been supered with imidacloprid contaminated supers none to only a few bees and no stored honey were present in those supers.
  6. In colonies that had been supered with uncontaminated supers the supers were full of bees and stored honey was present.
  7. In colonies that had been supered with imidacloprid contaminated supers there was less than half the amount of honey as compared to the colonies that had been supered with uncontaminated supers.

On November 20-22, I again went to Carrington, North Dakota. I met with Chris Charles and Mitch Charles. I personally know that many of the canola fields in the Carrington area of North Dakota were planted with seed treated with Gaucho. I personally observed the effects of imidacloprid on honey bee colonies. I inspected 21colonies. Seventeen of the colonies were dying from the effects of imidacloprid. Eight colonies had 400-500 fresh dead bees in front of each colony. Nine colonies had more than 1,000 dead bees on the bottom board of each colony. They were so demoralized from the imidacloprid they were unable to remove the dead bees from the colony.

I again went to Carrington, North Dakota on August 24, 2004. I spent several days there with the beekeepers and consultants from Bayer and inspected honey bee colonies in a number of apiaries. I personally know that many of the canola fields in the Carrington area of North Dakota were planted with seed treated with Gaucho. I personally observed typical symptoms of bee poisoning from the effects of imidacloprid on the bees. I also visited with the following beekeepers Chris Charles, Mitch Charles, Lonnie Thompson and Dewey Robson's foreman Bruce Chambers.


All my opinions are made with a reasonable degree of scientific certainty. In my opinion, imidacloprid from the Gaucho seed treatments caused the dead bees, erratic bee behaviour, colonies to dwindle, dead colonies and loss of honey production to the plaintiffs.

My opinion is confirmed by the results from ADPEN Laboratories. In their analytical tests for imidacloprid in dead bees and comb from the Charles they found very high residues of imidacloprid.

I conclude the injury to the honey bees belonging to the plaintiffs was caused by imidacloprid and my conclusion is confirmed by the imidacloprid residues found in the bees and wax by ADPEN Laboratories.

Literature Reviewed

ADPEN Laboratories, INC. Results of analytical tests for imidacloprid in bees and wax from Charles Bayer. All Documents Bayer Submitted for Case.

Armengaud, C., M. Lambin and M. Gauthier. 2002. Effects of imidacloprid on the neural process of memory in honey bees. In: Honey Bees; Estimating the Environmental Impact of Chemicals.

Armengaud, c., J. Ait-Oubah, N. Causse, and M. Gauthier. 2001. Nicotinic acetylcholine receptor ligands differently affect cytochrome oxidase in the honeybee brain. Neuroscience Letter 304:97-101.

Bonmatin, J.M., P.A. Marchand, R. Charvet and M.E. Colin. 2004. Fate of systemic insecticides in fields (imidacloprid and fipronil) and risks for pollinations. First European Conf. of Apidology, Udine: 118.

Bonmatin, J.M., 1. Moineau, R. Charvet, C. Fleche, M.E. Colin and E.R. Bengsch. 2003. A LCI APCI-MS/MS method for analysis of imidacloprid in soils, in plants, and in pollens. Anal. Chem.75:2027-2033.

Colin, M.E., Y. LeConte and J.P. Vermandere. 2001. Managing nuclei in insectproof tunnel as an observation tool for foraging bees: sub lethal effects of deltamethrin and imidacloprid. In Hazards of Pesticides to Bees.

Clay,. H. 2003 Canadian Honey Council. Decourtye, A. 2000. Impact of imidacloprid and its main metabolites on the honeybee Apis mellifera L.: Effects of chronic exposures on mortality and learning.

Guez, D., L.P. Belzunces and R. Maleszka. 2003. Effects ofimidacloprid metabolites on habituation in honeybees suggest the existence of two subtypes of nicotinic receptors differentially express during adult development. Pharmacology, Biochemistry and Behavior 75:217-222.

Guez, D., S. Suchail, M. Gauthier, R. Maleszka and L.P. Belzunces. 20011 Contrasting effects ofimidacloprid on habituation in 7-and 8-day-old honeybees (Apis mellifera).

Gustafson LLC. Undated. Gaucho 600 Flowable Label. 1400 Preston Road, Suite 400, Plano, TX 75093 Hellipointer, E. 1994. Degradation and translocation of imidacloprid (NTN 33893) under field conditions on a lysimer. Miles Report No. 106426, pp. 1-71. Miles Inc., Agricultural Division: Kansas City, MO .

Lambin, M, C. Amengaud and S. Raymond. 2001. Imidacloprid-induced facilitation of the proboscis extension reflex habituation in the honeybee. Arch. Insect Biochem and Physio. 48:129-134.

Mayer, D.F. and !.D. Lunden. 1997. Effects of imidacloprid insecticide on three bee pollinators. Hort. SCI. 29:93-97

Medrzycki, P., R. Montanari, L. Bortolotti, AG. Sabatini, S. Maini and C Porrini. 2002. Effects of imidacloprid administered in sub-lethal doses on honey bee behaviour: Laboratory tests. In Proc. 8th Internat. Sym on Hazards of Pesticides to Bees.

Nauen,R., E. Kintscher, and R. Schmuck. 2001. Toxicity and nicotinic acetylcholine receptor interaction of imidacloprid and its metabolites in Apis mellifera (Hymenoptera:Apidae) Pest Management Sci. 57:577-586.

Scholz, K. and M. Spiteller. 1992. Influence of groundcover on the degradation of 14-C Imidacloprid in soil. Brighton Crop Protection Conference. Pests and Diseases. Pp.833-888 .

Stark, J.D., P.C. Jepson and D. F. Mayer. 1995. Limitations to use of topical toxicity data for predictions of pesticide side effects in the filed. J. Econ. Entomol. 88:1081-1088.

Steffens, Robert. Deposition taken on 27 July 2006.

Suchail, S., D. Guez and L.P. Belzunces. 2000. Characteristics of imidacloprid toxicity in two Apis mellifera subspecies. Environ. Tox. and Chern. 19:1902-1950.

Zafeiridou, G. and G. Theophilidis. Modulation of the respiratory rhythm in honeybees, Apis mellifera macedonica, caused by the insecticide imidacloprid in the low namomolar concentrations range. First European Conf. of Apidology, Udine: 121.

Zunic, A. and A. Cokl. 2004. Effects of subletal doses of imidacloprid on honeybees' freezing response, after cuitcular exposure. First European Conf. of Apidology, Udine: 120.


By Daniel F. Mayer, Ph.D. 1 August 2006

Opinions and Conclusion

I relied on the material listed in my 31 July 2006 report for my opinions and conclusion. I also relied on the following: interview of plaintiffs; inspections of honey bee operations; and depositions of the plaintiffs for my opinions and conclusion.


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