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Diflufenican

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Diflufenican
Names
IUPAC name
N-(2,4-difluorophenyl)-2-[3-(trifluoromethyl)phenoxy]pyridine-3-carboxamide
Other names
diflufenicanil; N-(2,4-Difluorophenyl)-2-(3-(trifluoromethyl)phenoxy)nicotinamide
Identifiers
ChemSpider
ECHA InfoCard 100.122.360 Edit this at Wikidata
Properties
C19H11F5N2O2
Molar mass 394.301 g·mol−1
Appearance White Powder
Density 1.438 g/cm3[1]
Melting point 160[2][1] °C (320 °F; 433 K)
Boiling point 376[1] °C (709 °F; 649 K)
Insoluble[2] – 0.05mg/L[3]
Solubility in acetone Soluble[2] – 100 g/L[3]
Solubility in ethylene glycol Soluble[4]
Solubility in ethanol Soluble[4]
Vapor pressure 0.07 mPa (30°C)[3]
Hazards
GHS labelling:
GHS09: Environmental hazard[5]
H411, H413[5]
P262, P273, P352, P391[5]
Flash point 181.3°C, 358.3°F[1]
Lethal dose or concentration (LD, LC):
>5000 mg/kg (rat, oral)[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Diflufenican (sometimes called DFF) is a herbicide used to control weeds including wild radish and wild turnip weeds or suppress capeweed, crassula, marshmallow or shepherd's purse, in clover pasture, lupins, lentils or field peas. It has seen use in Australia,[6] Europe, and in Feb 2024 registered in North America by the PMRA, EPA registration pending, for use on soybean and corn.[7]

376 tonnes of diflufenican active ingredient were used in the United Kingdom in 2020.[8]

Discovery

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Diflufenican was discovered with a common intermediate method (CIM),[9] and trialled in England and France between 1981 and 1983.[10] A simple intermediate is reacted and recombined. Diflufenican derives from 2-chloronicotinic acid, one product replaced the chlorine with a phenoxy group, one receives an aniline group, and then both are recombined into DFF.[9]

Toxicology

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The Australian Acceptable Daily Intake for diflufenican is set at 0.2 mg/kg/day, based on the NOEL of 16.3 mg/kg/day.[5] With an oral rat LD50 of >5000 mg/kg, diflufenican is not toxic to mammals,[2] nor to honeybees.[7][3]

By inhalation, the air LC50 is 2.34 mg/L, for rats. It is not irritating to the skin and eyes, tested on rabbits. In dogs over 90 days, a NOEL of 1000 mg/kg daily was found. By the Ames Test, it is non-mutagenic.[3]

To birds, diflufenican is not toxic. LD50 of >2150 mg/kg (quail), >4000 mg/kg (mallard ducks). For fish, the LC50 is 56–100 mg/L (rainbow trout), 105 mg/L (carp). DFF does not inhibit the growth of algae. Non-toxic to earthworms.[3]

Environmental Fate

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Diflufenican has high persistence in soil but has low mobility, and low bioaccumulative potential. It is toxic to aquatic life.[5] (See toxicology section for details).

Diflufenican rapidly metabolises in cereals to carbon dioxide via nicotinamide and nicotinic acid, and leaves no detectable residue after 200–250 days. In soil, similar degradation to CO2 is seen, with a half life of 15 to 30 weeks.[3]

Effect and Mechanism

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Targeted weeds display bleaching and chlorotic spotting, followed by pink and purple foliage and necrosis. Symptoms typically begin 3–4 days after application.[6] DFF's residual activity may last 8 weeks.[11]

Diflufenican inhibits carotenoid synthesis, without which photosynthesis begins to fail and the plant is vulnerable to damage from sunlight, causing growth cessation and necrosis.[7] It is absorbed by germinating seedlings. Usually applied at 125–250 g/ha pre-emergence or shortly after, often with other cereal herbicides.[3]

Diflufenican is a Group F, (Australia), F1 (global) or Group 12 (numeric) resistance class herbicide.[12]

Regulations

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Diflufenican is registered in the United Kingdom and the European Union, for professional and amateur use.[13] It is also approved in New Zealand.[14]

Applications

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Diflufenican is often applied at 50–100 g/ha,[11][6] or lower if part of a herbicide mixture, e.g. as little as 9 g/ha with bromoxynil.[15]

List of Targetted Weeds

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Diflufenican has shown control over: wild radish, wild turnip, turnip weed,[6] multiply herbicide resistant waterhemp[7] (applied pre-emergence), hedge mustard, Indian hedge mustard, charlock, deadnettle, prickly lettuce, pheasant's eye,[11] Galium aparine, ivy-leaved speedwell and Veronica persica;[10] and suppression of capeweed, crassula, night-scented stock, marshmallow, corn gromwell, chickweed, hyssop loosestrife, Skeleton weed, speedwell, amsinckia, Paterson's curse, rough poppy, sorrel, toad rush, stinging nettle and shepherd's purse.[11]

List of Co-used Pesticides

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Diflufenican has been sold in formulations containing (not limited to): isoproturon, ioxynil, mecoprop, bromoxynil, diclofop-methyl,[3] and pendimethalin.[16] Furthermore, compatibility is reported with: simazine, alpha cypermethrin, metribuzin and quizalofop, in addition to compatibility with most grass herbicides.[11]

List of Crops Applied On

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Diflufenican has been applied to crops, including: wheat, barley,[3] field peas, lentils, lupins and oilseed poppy.[11]

Tradenames

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  • Diflufenican
  • DFF
  • Brodal

References

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  1. ^ a b c d "Diflufenican Safety Data Sheets". EChemi.
  2. ^ a b c d e "Diflufenican Standard SDS" (PDF). FujiFilm. Retrieved 7 August 2024.
  3. ^ a b c d e f g h i j Tomlin, Clive (1994). The Pesticide Manual Incorporating the Agrochemicals Handbook (Tenth ed.). State Library of Western Australia: The Royal Society of Chemistry. p. 335. ISBN 0-948404-79-5.
  4. ^ a b Li, Wentian; Wang, Juan; Li, Shuguang; Liu, Yinping; Li, Siqi; Wu, Junfeng (2023). "Solubility modeling, dissolution and solvation thermodynamics, and solute–solvent interactions of diflufenican in aqueous aprotic and protic cosolvents". The Journal of Chemical Thermodynamics. 179: 106981. doi:10.1016/j.jct.2022.106981.
  5. ^ a b c d e "4Farmers Diflufenican 500 SDS" (PDF). 4Farmers Australia.
  6. ^ a b c d "4Farmer Diflufenican 500 Infosheet" (PDF). 4Farmers Australia.
  7. ^ a b c d Soltani, Nader; Willemse, Christian; Sikkema, Peter H. (3 June 2024). "Biologically effective dose of diflufenican applied preemergence for the control of multiple herbicide-resistant waterhemp in corn" (pre-proof). Weed Technology. doi:10.1017/wet.2024.42.
  8. ^ "PESTICIDE USAGE SURVEY REPORT 295: ARABLE CROPS IN THE UNITED KINGDOM 2020" (PDF). Land Use & Sustainability Team.
  9. ^ a b Changling, Liu; Guan, Aiying; Yang, Jindong (17 December 2014). "Efficient Approach To Discover Novel Agrochemical Candidates: Intermediate Derivatization Method". Journal of Agricultural and Food Chemistry. 64 (1). doi:10.1021/jf5054707.
  10. ^ a b Cramp, Michael C.; Gilmour, James; Hatton, Leslie R.; Hewett, Richard H.; Duck, Donald; Nolan, Christopher J.; Parnell, Edgar W. (30 Oct 1985). "Design and Synthesis of N-(2,4-difluoropheny1)-2-(3-trifluoromethylphenoxy)-3-pyridinecarboxamide (diflufenican), a Novel Pre- and Early Post-emergence Herbicide for Use in Winter Cereals". Pesticide Science. 18: 15–28. doi:10.1002/ps.2780180103.
  11. ^ a b c d e f "4Farmers Diflufenican 500 Label" (PDF). 4Farmers Australia. Retrieved 7 August 2024.
  12. ^ "Australia Herbicide Classification Lookup". Herbicide Resistance Action Committee.
  13. ^ "Agency Opinion on the classification and labelling of diflufenican (ISO)" (PDF). www.hse.gov.uk. United Kingdom Health and Safety Executive. June 2022. Retrieved 13 September 2024.
  14. ^ "APPROVAL: DIFLUFENICAN" (PDF). Environmental Protection Authority of New Zealand. 30 April 2021.
  15. ^ "4Farmers Bromoxynil DFF Label" (PDF). 4farmers.com.au. 4Farmers Australia. Retrieved 28 August 2024.
  16. ^ Impey, Louise (2015). "How agchem firms are breathing new life into old pesticide actives". Farmers Weekly.
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