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Mecoprop, commonly known as MCPP, is a chlorophenoxy herbicide that was registered in 1960s. This initial formulation consisted of two chemical isomers in equal proportion, only one of which is the active herbicide. New technologies in the 1980s allowed for the creation of products with higher concentrations of the active isomer, at an approximate 93-95% purity. The new formulation was named mecoprop-p, or MCPP-p (#EPA).

MCPP-p is commonly used to control a variety of weeds. It is used extensively on turf, such as residential lawns and sports fields.

Mecoprop may be marketed as Kilprop, Mecopar, Triester-II, Mecomin-D, Triamine-II, Triplet, TriPower, Trimec, Trimec-Encore, and U46 KV Fluid (#EXTOXNET).

Chemical Description

Mecoprop-p is a colorless, odorless crystal. MCPP-p acid is the parent of several other formulations including MCPP-p dimethylamine salt and MCPP-p potassium salt. Some forms are water soluble. Mecoprop-p does not bond strongly to soil (#EPA). In tests with artificial light, MCPP-p has a half-life of 83 days (#NCAMP).

Commercially, mecoprop-p is available as granular formulations, emulsifiable concentrates, water-soluble concentrates, wettable powders, and ready-to-use solutions (#EPA).


MCPP-p is used on ornamental and recreational turf, sod farms, roadsides, industrial sites, and rights-of-way (#EPA). It is used for the post-emergent control of broadleaf weeds including prostate chickweed, stitchwort, ground ivy, knowtweed, clover,and plaintain (#NCAMP).

Of the estimated 1-6 million pounds of mecoprop used annually in the United States, 96% is used on turf, including residential lawns, sports turf, and commercial sod farms (#NCAMP).

According to the MCPP-p Task Force, total annual domestic usage of MCPP-p is approximately 5 million pounds: >97% is applied to residential lawns, 2% is applied to golf courses, and <1% is applied to turf farms and other uncultivated non-agricultural land (#EPA).

Human Health Effects

Mecoprop-p has a slight acute toxicity. Studies on rats indicate an acute oral LD50 of 775 mg/kg. Eye irritant tests on rabbits found that opacity, irritation, and discharge may occur. The Cancer Assessment Review Committee found some evidence of carcinogenicity, but not enough to classify MCPP-p as a carcinogen (#EPA). Kidney damage was found in rats fed doses 9 mg/kg and 27 mg/kg for 90 days (#NCAMP).

Chlorophenoxy compounds are understood to cause skin and eye irritation, coughing, burning sensations in the chest, dizziness, headache, vomiting, diarrhea, confusion or bizarre behavior, increased heart rate, and kidney failure (#PANNA).

Environmental Health Effects

In plants, MCPP-p increases cell wall plasticity, and stimulates protein synthesis and ethylene production. This interferes with normal plant growth, damaging vascular tissue (#EPA).

MCPP-p has a slight acute toxicity to mammals. It also slightly toxic to birds and freshwater fish. The acute oral LD50 in bobwhite quail is 700 mg/kg. In rainbow trout, the LC50 is 124 ppm. There is little to no acceptable data regarding the toxicity to many other aquatic organisms, nor is there reliable data on the toxicity to non-target plants (#NCAMP). Bioaccumulation is not expected to be a significant source of contamination (#EPA).

Due to its solubility and low affinity for soil, mecoprop-p can easily leach. However, the level of drinking water contamination falls below the level of concern for acute toxicity (#EPA).


Mecoprop-p is registered for general use, but has no registration for use on food crops.

Precautionary Notes

Some labels that read MCPP are referring to MCPP-p. Mecoprop has a high mobility in soil. Use caution if near water sources.


Environmental Protection Agency. Reregistration Eligibility Decision for Mecoprop-p. (August 2007) [Accessed 8/01/10].

Extension Toxicology Network. Mecoprop. (1996). [Accessed 8/01/10].

National Coalition Against the Misuse of Pesticides. Chemical Watch Factsheet: Mecoprop. [Accessed 8/01/10].

Pesticide Action Network North America. Mecoprop-p. [Accessed 8/01/10].

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