The Coalition for a Healthy Ottawa

Fact Sheet on "Merit" insecticide (grub killer)
(active ingredient: Imidacloprid)
(Instead of using Merit please consider using natural Nematodes, which eat grubs!


- Imidacloprid is the active ingredient used in the grub killing pesticide named "Merit"
(Merit and Bayer are trademarks of Bayer CropScience)

- imidacloprid is a chlorinated nicotinoid compound, that affects the nervous system

- Imidacloprid is manufactured by Bayer

- Imidacloprid is banned in Italy, Germany, Slovenia, and restricted in France (see: source).

- Imidacloprid works by fitting into nerve receptors meant to receive the neurotransmitter acetylcholine (ACh).  By blocking these acetylcholine receptors, an excess of acetylcholine accumulates causing paralysis and eventual death

- Adverse effects of imidacloprid may include apathy, difficulty breathing, loss of the ability to move, staggering, trembling and spasms[1]

- The thyroid is particularly sensitive to exposure of imidacloprid, which is linked to causing thyroid lesions.[2]

- Imidacloprid is very toxic to earth worms,[3] with an LD50 of between 2 and 4 parts per million in soil

- Imidacloprid is extremely toxic to honey bees  [see product label example]  and is restricted in France because of plummeting bee populations.

- Imidacloprid kills parasitic wasps that control grub larvae.  This is counter-productive, setting the stage for repeated, more extensive grub infestations.

- Imidacloprid is applied to seeds because it acts as a bird repellent.  Birds such as starlings and robins eat very large numbers of grubs.  Repelling this important natural control would be counter-productive.

- Imidacloprid use has been linked to eggshell thinning in birds.[4]

- Imidacloprid is highly toxic to certain species including the house sparrow,[5] pigeon, canary and Japanese quail[6]

- Imidacloprid severely limits the mobility of lady beetles[7] and other predatory insects such as marid bugs and lacewings.[8]

- At exposures of 0.2 ppm, imidacloprid has been shown to cause deformed sperm and 0.5 ppm for DNA damage[9].

- When imidacloprid was fed to pregnant rabbits between the sixth and eighteenth days of pregnancy, there was an increase in the number of miscarriages and an increase in the number of offspring with abnormal skeletons.[10]  Imidacloprid-exposed rats also gave birth to smaller offspring.

- The label stipulates that food crops cannot be planted for a year after imidacloprid application.  Thus, two growing seasons would have elapsed before harvest.  Our children are not afforded the protection of two growing seasons before exposure to turf that has been treated with imidacloprid. 

- Breakdown of imidacloprid in the environment is very complex and slow, and some degradation products are more toxic than the parent compound.  Thus, the possibility exists that soil will become more toxic rather than less toxic with the passage of time.  This may not happen if sufficient pesticide was washed away, but pollution of our water is not a desirable outcome either.

- Compared with 11 other popular pesticides, imidacloprid moved more quickly through soil than any of the other pesticides tested.[11]  The EPA places imidacloprid in category I as having the highest leaching potential. 

- There is a potential for the compound to move through sensitive soil types including porous, gravelly, or cobbly soils, depending on irrigation practices [12]

- The New York State Department is concerned that imidacloprid is found in an "increasing number of detections in private homeowner wells" -- click here to view

- Imidacloprid is extremely long-lasting.  It has a half-life up to 730 days, yet is approved for annual applications. It has been observed to build up over the years, in agricultural application.

- Constant exposure to pesticides fosters pesticide resistance. Resistance to imidacloprid has appeared within as little as 2 years.  Insecticides should be reserved for when they are badly needed to protect public health.

- Inert ingredients / contaminants of the imidacloprid product "Merit" have been reported to include naphthalene and crystalline silica. Both napthalene and crystalline silica are proven cancer causing agents  [13],[14]

- Imidacloprid degrades into toxic, persistent, 2-chloropyridine. This was not considered in the federal assessment.

- Historically, imidacloprid was granted at least three temporary registrations by the PMRA, in spite of missing environmental fate data.

- Commissioner for the Environment, Johanne Gélinas, has repeatedly criticised the Pest Management Regulatory Agency (PMRA) for granting temporary registrations when important data is lacking.

- As of June 12, 2007, the PMRA as registered four commercial insecticides containing Imidacloprid:

Merit Solupack Insecticide (Reg. No. 25932) 
Merit 0.5 G insecticide (Reg. No. 25933), 

The PMRA still does not have complete environmental fate data.

In 2003, 527 kg of imidacloprid was used for agriculture purposes in Ontario, while in Ottawa 776 kg of insecticides including imidacloprid and sevin was used on turf.  Public statements from lawn pesticide applicators indicated that they mainly apply imidacloprid.  It would therefore appear that the largest use of imidacloprid in Ontario is for turf.

For additional studies on imidacloprid, please click here (Fact Sheet with 18 references).

Recent News:

- On August 25, 2008, The Coalition against Bayer Dangers initiated a lawsuit against Werner Wenning, chairman of the Bayer AG Board of Management, and Bayer CropScience for "marketing dangerous pesticides and thereby accepting the mass death of bees all over the world." The alleged dangerous Bayer pesticides are imidacloprid (used in "Merit") and clothianidin.  Both are "neonicotinoid" insecticides.  Harro Schultze, attorney of the Coalition against Bayer Dangers, said "we're suspecting that Bayer submitted flawed studies to play down the risks of pesticide residues in treated plants”  For more info, please see: The Coalition against Bayer Dangers News item 1, News item 2 and PMRA's 2004 assessment of Clothianidin - which on page 30 found studies "to be deficient in design and conduct".

- August 2008, The Natural Resources Defense Council filed a lawsuit seeking the release of U.S. Environmental Protection Agency (EPA) test data for Bayer's neonicotinoid pesticides (imidacloprid and clothianidin).  For details, click hereUp

Imidacloprid Breakdown –
Environmental Fate

Presented to Ottawa City Council
by Bayer, manufacturer of "Merit"

August, 2004


"Unidentified" fate of Imidacloprid

----> + CO2

6-chloronicotinic acid --> 2-chloropyridine + carbon dioxide



[1] Doull, J., C.D. Klassen, and M.O. Amdur (eds.). 1991. Cassarett and Doull's Toxicology. The Basic Science of Poisons. Fourth Edition. Pergamon Press, Elmsford, NY.

[2] U.S. EPA. Office of Pesticides. 1994. Toxoneliners: Imidacloprid. Washington, D.C., Jan. 3, p. 1.

[3] Zang, Y. et al. 2000. Genotoxicity of two novel pesticides on earthworm, Eisenia foetida. Chemosphere 39:2347-2356.

[4] U.S. EPA. Office of Pesticide Programs. 1994. Pesticide fact sheet: Imidacloprid. Washington, D.C., Mar. 18.

[5] U.S. EPA. Office of Pesticide Programs. 1994. Pesticide fact sheet: Imidacloprid. Washington, D.C., Mar. 18.

[6] U.S. EPA. Office of prevention, Pesticides and Toxic Substances. 1994. Imidacloprid, acian 6(a) (2) submittals. Memo from A.F. Mciorowski, Ecological Effects Branch, to D. Edwards, Registration Division, Washington, D.C.

[7] Smith, S.F. and V.A. Krischik. 1999. Effects of systemic imidacloprid on Coleomegilla maculate. Environmental Entimology. 28:1189-1195.

[8] Mizell, R.F. and M.C. Sconyers. 1992. Toxicity of imidaclprid to selected arthropod predators in the laboratory. Flor. Entomol. 75:277-280.

[9] Zang, Y. et al. 2000. Genotoxicity of two novel pesticides on earthworm, Eisenia foetida. Chemosphere 39:2347-2356.

[10] U.S. EPA Office of Prevention, Pesticides and Toxic Substances. 1993. Imidacloprid. Evaluation of toxicity data submitted and identification of outstanding toxicology data requirements.

[11] Vollner, L. and D. Klotz. 1997. Leaching and degrqadation of pesticides in groundwater layers. Environmental Behaviour of crop protection chemicals. Vienna, Austria: International Atomic Energy Agency. Pp. 187-203.

[12] Jenkins, J.J. 1994. Use of Imidacloprid for Aphid Control on Apples in Oregon. Potential for Ground and Surface Water Contamination. Department of Agricultural Chemistry. Oregon State University, Corvallis, OR.

[13] International Agency for Research on Cancer. 1997. Silica.

[14] National Toxicology Program. Undated. Toxicology and carcinogenesis studies of naphthalene (CAS No. 91-20-3) in F344/N rats (inhalation studies).


Fact sheet updated Sept. 16, 2008


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Last updated:April 16, 2009

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