# Lambda cyhalothrin
**Lambda cyhalothrin** (λ-cyhalothrin) is a synthetic pyrethroid insecticide and acaricide used to control a broad range of pest insects and mites in agriculture, public health, structural pest management, and households. It is an enriched isomer of cyhalothrin, with CAS number 91465-08-6 and molecular formula C23H19ClF3NO3.[1](https://www3.epa.gov/pesticides/endanger/litstatus/effects/redleg-frog/2012/lambda-cyha/appendix-j.pdf) • [2](https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1016QDM.TXT) Sold under trade names including Karate, Matador, Demand, Icon, Saber, and Warrior, it is among the most widely used pyrethroids worldwide.[3](https://extoxnet.orst.edu/pips/lambdacy.htm) • [4](https://doi.org/10.1016/j.envpol.2023.122694)
| Key fact | Detail |
|---|---|
| Identity | Synthetic pyrethroid insecticide and acaricide; CAS 91465-08-6; molecular weight 449.9 g/mol; enriched isomer of cyhalothrin[1](https://www3.epa.gov/pesticides/endanger/litstatus/effects/redleg-frog/2012/lambda-cyha/appendix-j.pdf) • [2](https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1016QDM.TXT) |
| Uses | Food and feed crops, livestock, turf, shelterbelts, structural sites, ornamentals, and public health vector control (mosquitoes, cockroaches, ticks, flies)[5](https://www.canada.ca/en/health-canada/services/consumer-product-safety/reports-publications/pesticides-pest-management/decisions-updates/reevaluation-decision/2021/lambda-cyhalothrin.html) |
| Soil behavior | Koc 180,000; field half-lives of 4 to 12 weeks; little potential for groundwater contamination[3](https://extoxnet.orst.edu/pips/lambdacy.htm) |
| Aquatic chemistry | Stable at pH below 8; hydrolyzes to HCN and an aldehyde under alkaline conditions; photolysis half-life under 10 minutes under UV but over 3 weeks under natural irradiation[6](https://pubmed.ncbi.nlm.nih.gov/18418954/) |
| Toxicity benchmarks | Highly toxic to bees (oral LD50 38 ng/bee); EPA Toxicity Class II; EFSA ADI 0.0025 mg/kg bw per day and ARfD 0.005 mg/kg bw[3](https://extoxnet.orst.edu/pips/lambdacy.htm) • [7](https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2024.8816) |
| Market size | $1.25 billion in 2020, projected to exceed $3.8 billion by 2027[4](https://doi.org/10.1016/j.envpol.2023.122694) |
| Regulatory status | EU plant protection approval expires 31 August 2026 (candidate for substitution); EU biocidal PT18 approval runs to 30 September 2028[8](https://echa.europa.eu/legislation-obligation/-/obligations/100.101.414) • [9](https://echa.europa.eu/information-on-chemicals/biocidal-active-substances/-/disas/substance/100.101.414) |
## Chemistry and mode of action
Lambda cyhalothrin belongs to the pyrethroid class, synthetic compounds modeled on the pyrethrins of chrysanthemum. Like other pyrethroids, it targets the insect nervous system; other proposed ways the class works are blocking inhibition mediated by gamma-aminobutyric acid (GABA), altering nicotinic cholinergic signaling, promoting the release of noradrenaline, and affecting calcium ions.[10](https://pubchem.ncbi.nlm.nih.gov/compound/lambda-CYHALOTHRIN) It kills by contact and ingestion, and commercial formulations include emulsifiable concentrates, wettable powders, capsule suspensions (microencapsulated), and ultra-low-volume liquids.[3](https://extoxnet.orst.edu/pips/lambdacy.htm) • [11](https://www.lifescientific.com/en/products/life-scientific-lambda)
The substance is a 1:1 reaction mass of two stereoisomers, (R)-α-cyano-3-phenoxybenzyl (1S,3S)-3-[(Z)-2-chloro-3,3,3-trifluoropropenyl]-2,2-dimethylcyclopropanecarboxylate and its (S,1R,3R) counterpart.[9](https://echa.europa.eu/information-on-chemicals/biocidal-active-substances/-/disas/substance/100.101.414) A closely related single-isomer product, gamma-cyhalothrin, is regulated separately in some jurisdictions.[12](https://www.epa.gov/sites/default/files/2020-10/documents/lambda-gamma-cyhalothrin-reg-review-pid.pdf)
## Uses
Lambda cyhalothrin controls aphids, beetle pests such as the [Colorado potato beetle](https://www.edgepedia.org/colorado-potato-beetle) and adult [Japanese beetle](https://www.edgepedia.org/japanese-beetle), caterpillars and butterfly larvae, grasshoppers, and mites on crops including cotton, cereals, hops, potatoes, vegetables, and ornamentals.[3](https://extoxnet.orst.edu/pips/lambdacy.htm) • [1](https://www3.epa.gov/pesticides/endanger/litstatus/effects/redleg-frog/2012/lambda-cyha/appendix-j.pdf) In public health it is used against mosquitoes, cockroaches, ticks, and flies that can act as disease vectors, and World Health Organization specifications cover wettable powder, emulsifiable concentrate, and slow-release capsule suspension forms for indoor residual spraying, space spraying, and treatment of mosquito nets.[13](https://extranet.who.int/prequal/sites/default/files/doc_parts/WHOVC-SP_Lambda-cyhalothrin_2023.pdf) Structural uses include termite control, and a pour-on formulation is applied along the backline of beef cattle against lice and horn flies.[1](https://www3.epa.gov/pesticides/endanger/litstatus/effects/redleg-frog/2012/lambda-cyha/appendix-j.pdf)
The United States, China, and India are the main producers and consumers, with Thailand, Australia, Japan, Germany, and Russia among countries expected to increase consumption as cultivated area grows.[4](https://doi.org/10.1016/j.envpol.2023.122694)
## Environmental fate
Lambda cyhalothrin is moderately persistent in soil, with reported field half-lives of four to 12 weeks and a high affinity for soil organic matter (Koc 180,000), so it is not expected to be appreciably mobile and poses little groundwater contamination risk; leaching of the compound and its degradates was minimal in field studies.[3](https://extoxnet.orst.edu/pips/lambdacy.htm) [Breakdown](https://www.edgepedia.org/breakdown) in soil proceeds by hydrolysis of the central ester bond and oxidation, yielding products similar to those formed in mammalian systems.[3](https://extoxnet.orst.edu/pips/lambdacy.htm)
In water, the compound is quite stable below pH 8 but hydrolyzes to hydrogen cyanide and an aldehyde under alkaline conditions. Although relatively photostable under natural sunlight, with a half-life above three weeks, it photolyzes rapidly under ultraviolet irradiation, with a half-life under 10 minutes.[6](https://pubmed.ncbi.nlm.nih.gov/18418954/) Dissolved residues decrease quickly when suspended solids, algae, macrophytes, or animals are present because the molecules adsorb strongly to particulates and plants; adsorbed molecules degrade more slowly but their short-term bioavailability in the water column is reduced, which can mitigate acute toxicity to aquatic organisms.[6](https://pubmed.ncbi.nlm.nih.gov/18418954/) This rapid dissipation from the water phase has been a key factor in refining European aquatic risk assessments for water-column organisms, where spray drift is the main entry route from agricultural uses.[14](https://pubs.acs.org/doi/10.1021/bk-2008-0991.ch015)
Despite these mitigating processes, widespread use has left residues in sediment that have been found toxic to fish and amphipods. Measured environmental concentrations include 0.98 µg/L in sediments from Costa Rican agroecosystems and 0.35 to 0.80 µg/L in surface waters. Runoff mitigation can be achieved by reducing runoff volume and suspended solid content through wetlands, detention ponds, or vegetated ditches.[6](https://pubmed.ncbi.nlm.nih.gov/18418954/) • [4](https://doi.org/10.1016/j.envpol.2023.122694)
## Ecotoxicity
In laboratory studies lambda cyhalothrin is highly toxic to fish and invertebrates.[14](https://pubs.acs.org/doi/10.1021/bk-2008-0991.ch015) It is highly toxic to bees, with a reported oral LD50 of 38 ng/bee and a contact LD50 of 909 ng/bee, while toxicity to birds ranges from slightly toxic to practically non-toxic.[3](https://extoxnet.orst.edu/pips/lambdacy.htm) Bioconcentration in channel catfish has been reported as minimal with rapid depuration; a bioconcentration factor of 858 has been reported in an unspecified fish species, with concentration confined to non-edible tissues and rapid elimination.[3](https://extoxnet.orst.edu/pips/lambdacy.htm)
A 2023 review concluded that oxidative stress appears to be the main mechanism of lambda cyhalothrin toxicity in non-target organisms, linking it to hepatotoxicity, nephrotoxicity, neurotoxicity, and reproductive toxicity, and that antioxidants can significantly alleviate these toxic effects in experimental settings.[4](https://doi.org/10.1016/j.envpol.2023.122694) Reported effects in specific systems include pancreatic toxicity, hepatic oxidative damage in rodents, embryonic toxicity and oxidative damage in fish, and acute toxicity in pigeons.[4](https://doi.org/10.1016/j.envpol.2023.122694)
## Human health and regulation
EFSA's peer review, based on evaluation by Sweden as rapporteur member state, identified a high risk to aquatic organisms and established an acceptable daily intake of 0.0025 mg/kg body weight per day and an acute reference dose of 0.005 mg/kg body weight; the ADI was based on clinical signs of neurotoxicity in a 52-week dog study, the most sensitive endpoint reported.[15](https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2014.3677) • [7](https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2024.8816) The Joint FAO/WHO Meeting on Pesticide Residues maintains a group ADI of 0 to 0.02 mg/kg body weight and an ARfD of 0.02 mg/kg body weight for cyhalothrin including lambda-cyhalothrin, first set in 2007 and reaffirmed in 2018 and 2024.[16](https://apps.who.int/pesticide-residues-jmpr-database/pesticide?name=Cyhalothrin+%28includes+lambda-cyhalothrin%29)
In the United States, some lambda-cyhalothrin products are restricted to certified applicators, while others are available to the general public; it sits in EPA Toxicity Class II (signal word WARNING), and in 2020 the EPA proposed interim registration review decisions including removal of certain uses, personal protective equipment requirements, re-entry intervals, and pollinator and aquatic mitigation measures.[3](https://extoxnet.orst.edu/pips/lambdacy.htm) • [12](https://www.epa.gov/sites/default/files/2020-10/documents/lambda-gamma-cyhalothrin-reg-review-pid.pdf) • [18](https://www3.epa.gov/pesticides/chem_search/ppls/097702-00017-20260211.pdf) [Health Canada](https://www.edgepedia.org/health-canada)'s 2021 re-evaluation found continued registration acceptable with additional mitigation, but canceled uses on lettuce, condiment-type mustard seed, all feed uses, Crop Group 3-07 bulb vegetables, and most of Crop Group 20 oilseeds; retained uses carry measures such as vegetative filter strips, spray buffer zones, and restrictions on application during crop bloom.[5](https://www.canada.ca/en/health-canada/services/consumer-product-safety/reports-publications/pesticides-pest-management/decisions-updates/reevaluation-decision/2021/lambda-cyhalothrin.html) In the European Union, lambda cyhalothrin is approved for plant protection until 31 August 2026 and is listed as a candidate for substitution; for biocidal product-type 18 (insect control), approval runs to 30 September 2028 with Greece as evaluating authority.[8](https://echa.europa.eu/legislation-obligation/-/obligations/100.101.414) • [9](https://echa.europa.eu/information-on-chemicals/biocidal-active-substances/-/disas/substance/100.101.414)
## Resistance
Resistance has developed in some pest populations. In *Spodoptera frugiperda* (fall armyworm), the P450 enzyme inhibitor piperonyl butoxide significantly enhanced lambda cyhalothrin toxicity in resistant strains, indicating metabolic detoxification by cytochrome P450 enzymes as a resistance mechanism; the study's authors framed the results as input for resistance management strategies.[17](https://www.sciencedirect.com/science/article/pii/S0048357524001494)
## References
1. [Lambda-Cyhalothrin: Human Health Risk Assessment, Appendix J, US EPA](https://www3.epa.gov/pesticides/endanger/litstatus/effects/redleg-frog/2012/lambda-cyha/appendix-j.pdf)
2. [Risks of Lambda-Cyhalothrin Use to Federally Threatened and Endangered Species, US EPA](https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1016QDM.TXT)
3. [EXTOXNET PIP: Lambda Cyhalothrin, Extension Toxicology Network, Oregon State University](https://extoxnet.orst.edu/pips/lambdacy.htm)
4. [Xu et al. (2023). Oxidative stress and mitochondrial damage in lambda-cyhalothrin toxicity. Environmental Pollution 338:122694](https://doi.org/10.1016/j.envpol.2023.122694)
5. [Re-evaluation Decision RVD2021-04, Lambda-cyhalothrin, Health Canada](https://www.canada.ca/en/health-canada/services/consumer-product-safety/reports-publications/pesticides-pest-management/decisions-updates/reevaluation-decision/2021/lambda-cyhalothrin.html)
6. [Environmental chemistry, ecotoxicity, and fate of lambda-cyhalothrin, PubMed (PMID 18418954)](https://pubmed.ncbi.nlm.nih.gov/18418954/)
7. [Targeted risk assessment of MRLs for lambda-cyhalothrin in poultry and eggs, EFSA Journal 2024;12(5):8816](https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2024.8816)
8. [Annex of Approved Active Substances for Plant Protection Products, ECHA](https://echa.europa.eu/legislation-obligation/-/obligations/100.101.414)
9. [Biocidal active substance factsheet: lambda-cyhalothrin PT18, ECHA](https://echa.europa.eu/information-on-chemicals/biocidal-active-substances/-/disas/substance/100.101.414)
10. [lambda-Cyhalothrin, CID 6440557, PubChem](https://pubchem.ncbi.nlm.nih.gov/compound/lambda-CYHALOTHRIN)
11. [LIFE SCIENTIFIC LAMBDA product page, Life Scientific](https://www.lifescientific.com/en/products/life-scientific-lambda)
12. [Lambda-Cyhalothrin and Gamma-Cyhalothrin Proposed Interim Registration Review Decision, US EPA (September 2020)](https://www.epa.gov/sites/default/files/2020-10/documents/lambda-gamma-cyhalothrin-reg-review-pid.pdf)
13. [WHO specification: Lambda-cyhalothrin (2023)](https://extranet.who.int/prequal/sites/default/files/doc_parts/WHOVC-SP_Lambda-cyhalothrin_2023.pdf)
14. [Aquatic Fate and Effects of Lambda-Cyhalothrin in Model Ecosystem Experiments, ACS Symposium Series (2008)](https://pubs.acs.org/doi/10.1021/bk-2008-0991.ch015)
15. [Conclusion on the peer review of the pesticide risk assessment of lambda-cyhalothrin, EFSA Journal 2014;12(5):3677](https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2014.3677)
16. [JMPR inventory of evaluations: Cyhalothrin (includes lambda-cyhalothrin), WHO](https://apps.who.int/pesticide-residues-jmpr-database/pesticide?name=Cyhalothrin+%28includes+lambda-cyhalothrin%29)
17. [Investigation of lambda-cyhalothrin resistance in Spodoptera frugiperda, Pesticide Biochemistry and Physiology](https://www.sciencedirect.com/science/article/pii/S0048357524001494)
18. [www3.epa.gov](https://www3.epa.gov/pesticides/chem_search/ppls/097702-00017-20260211.pdf)
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*Topic: Encyclopedia › Life and health › Applied biology and nonhuman health › Plant disease and plant protection › Pesticides › Insecticides › Pyrethroid insecticides*
*Initially written Oct 21, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license