Chemistry:Aminocyclopyrachlor

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Aminocyclopyrachlor (AMCP) is a selective, low-toxicity, auxin-mimicking herbicide that provides pre- and post-emergent control of broadleaf weeds on several non-food use sites including rights of way, wildlife management areas, recreational areas, turf/lawns, golf courses and sod farms. It was conditionally registered as Imprelis by DuPont in August 2010, and first used in Fall 2010,[1] though used experimentally since 2008 or before.[2]

Commercialization

After the first introduction in 2010, aminocyclopyrachlor was registered as an active ingredient in Australia in September 2014, but no product containing it was registered until Bayer's "Method 240 SL" in 2022. Before this, aminocyclopyrachlor was registered in New Zealand. Method is a 240 g/L soluble concentrate (SL), with aminocyclopyrachlor present as its potassium salt.[3]

DuPont registered DuPont DPX-KJM44 0.02G Lawn Herbicide + Fertilizer, a formulation of 0.02% AMCP with fertilizer in 2010,[4] although they voluntarily withdrew the registration in 2014.[5]

It may be applied at 312 g/Ha (active ingredient) in 100-400 L/Ha of water.[3]

Mechanism of action

Aminocyclopyrachlor is a systemic herbicide and acts by disrupting gene expression. It belongs to the pyrimidine carboxylic acid chemical family and mimics auxin which is a growth-regulating hormone in dicots including broadleaf terrestrial plants.[6] This causes undifferentiated cell division and elongation, with resulting appearance characteristic of auxin herbicide damage such as leaf twisting and curling.[7][8]


Chemical properties

It has some solubility in water, 2.81 g/L, more so in methanol, 36.7 g/L, and is practically insoluble in acetone, 0.96 g/L, dichloromethane, 0.2 g/L, acetonitrile, 0.65 g/L and n-octanol, 1.9 g/L. The low vapor pressure and Henry's law constant suggest that it will not disperse through the air. A low octanol/water partition constant of -1.12 (Log Pow) indicates it be not bioaccumulative, and technical grade aminocyclopyrachor should be stable for at least 2 years in normal storage conditions.[3]

Aminocyclopyrachlor is not flammable, explosive or auto-flammable and except for photo-degradation, the pure aminocyclopyrachlor isn't chemically incompatible with oxidising or reducing agents and is essentially non-hazardous.[3]

Ecotoxicity

Although auxin-mimicking herbicides are selectively toxic to dicots, some angiosperms are also affected. Due to the emergence of damage to some conifer species, the United States Environmental Protection Agency and DuPont advised professional applicators and residential consumers to not use Imprelis where Norway spruce or white pine trees are present on or near the property being treated.[1][9]

Residue

Tomato plants are the preeminent bioassay platform for testing auxin herbicide damage because they are extremely sensitive to it.[10][11] In a controlled greenhouse test, tomato plants were mulched with the remains of Norway spruce and honey locust trees that were damaged from exposure to AMCP that had been applied to adjacent turf grass more than a year prior to the tomato tests. The mulch (i.e. shredded foliage and stems) contained 4.7 to 276 ppb of AMCP. All of the AMCP-exposed tomato plants sustained visible damage while the unexposed controls showed no damage. Residual AMCP in the exposed tomato plants ranged from 0.5 to 8.0 ppb.[12]

The human ADI is 2.8 mg/kg/day, (224 mg/day for an 80 kg adult) based on a NOEL of 297 mg/kg/d in a 2 year long study on rats.[3]

Environmental behavior

As with aminopyralid, AMCP-contaminated soil, mulch, or compost should be excluded from sensitive crops or gardens. The dissipation half-life (DT50) time of AMCP has been measured at between 3 and >112 days in four soils from the Northern Great Plains.[13] More recently, the time required for 90% degradation (DT90) was found to be 622 to 921 days,[14] although an APVMA report cites a half-life in normal air of 42 hours, implying a wildly shorter DT90.[3] As a practical matter, all material in AMCP-treated areas should be regarded as permanently poisonous to tomatoes and other nightshades until proven safe.[citation needed]

Tradenames

Aminoicyclopyrachlor has been sold as "DPX-KJM44",[4] "Method", "Perspective", "Streamline", "Invora", "Viewpoint", "Plainview", "Navius", "TruVist" and "TruRange".[3] This list may be incomplete.

References

  1. ↑ 1.0 1.1 EPA (August 2011). "Imprelis and Investigation of Damage to Trees". http://www.epa.gov/pesticides/regulating/imprelis.html. 
  2. ↑ "Aminocyclopyrachlor (KJM44) Combinations for Total Vegetation and Marestail (Conyza canadensis) Contro". University of Kentucky. 2009. https://weedscience.mgcafe.uky.edu/files/aminocyclopyrachlor_for_marestail_and_total_vegetation_contr.pdf. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Cite error: Invalid <ref> tag; no text was provided for refs named apvma
  4. ↑ 4.0 4.1 "LABEL AND E.P.A. LETTER | DuPont KJM44 O.02G Lawn Herbicide + Fertilizer". E.P.A.. 27 Sep 2010. https://www3.epa.gov/pesticides/chem_search/ppls/000352-00811-20100927.pdf. 
  5. ↑ "Notice of Receipt of Requests To Voluntarily Cancel Certain Pesticide Registrations" (in en). 20 May 2014. https://www.federalregister.gov/documents/2014/05/20/2014-11685/notice-of-receipt-of-requests-to-voluntarily-cancel-certain-pesticide-registrations. 
  6. ↑ AMINOCYCLOPYRACHLOR 3–42 JMPR 2014 https://apps.who.int/pesticide-residues-jmpr-database/Document/222
  7. ↑ University of California, Division of Agriculture and Natural Resources. "Synthetic Auxins" (in en-US). https://herbicidesymptoms.ipm.ucanr.edu/MOA/Synthetic_Auxins/. 
  8. ↑ "Registration of the New Active Ingredient Aminocyclopyrachlor for Use on Non-Crop Areas, Sod Farms, Turf, and Residential Lawns". U.S. Environmental Protection Agency, Office of Pesticide Programs, Registration Division. August 24, 2010. pp. 4. https://docs.google.com/viewer?a=v&q=cache:vE5R3_7oWaoJ:www.regulations.gov/contentStreamer%3FobjectId%3D0900006480b405d8%26disposition%3Dattachment%26contentType%3Dpdf+&hl=en&gl=us&pid=bl&srcid=ADGEESjTxovvENcOMN-vSTDECzZaHsFElyl8S-vYJJenj80A_CdYBcWOF1wjO53RjL4bcnvAgdRZhucRdF3YCQBNbL_bJSrLwiOpWqSDhk_0bUh_LkObnhG3k8Vv8zCq_uNi07Z4BIKF&sig=AHIEtbQORx_SOUeYB9Z1LoTblCCQ7ORYhQ. Retrieved January 6, 2013. 
  9. ↑ EPA. "Imprelis and Investigation of Damage to Trees". https://www.epa.gov/pesticides/regulating/imprelis.html. 
  10. ↑ Israel, T.D., Rhodes, G.N. Jr., Wszelaki, A. Diagnosing Suspected Off-target Herbicide Damage to tomato, University of Tennessee Extension publication W 295-B, https://utia.tennessee.edu/publications/wp-content/uploads/sites/269/2023/10/W295-B.pdf
  11. ↑ , Ramda, K., Boyd, N., McAvoy, C., Suppress the weeds, not the crop, Vegetable and Specialty Crop News March 2019, https://swfrec.ifas.ufl.edu/docs/pdf/weed-science/2019-03-Herbicides%20phytotoxicity_VSC.pdf
  12. ↑ Patton et al.: AMCP in wood chips of damaged trees, Weed Technology 2013 27:803–809, https://oisc.purdue.edu/pesticide/pdf/wt-d-13-00066-1.pdf
  13. ↑ Conklin KL, Lym RG. Effect of Temperature and Moisture on Aminocyclopyrachlor Soil Half-Life. Weed Technology. 2013;27(3):552–556. doi:10.1614/WT-D-12-00147.1
  14. ↑ Takeshita, V., Mendes, K.F., Junqueira, L.V. et al. Quantification of the Fate of Aminocyclopyrachlor in Soil Amended with Organic Residues from a Sugarcane System, Sugar Tech (May–June 2020) 22(3):428–436 https://doi.org/10.1007/s12355-019-00782-1



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