Lambda-cyhalothrin (lambda-cyhalothrin)

Lambda-cyhalothrin is a synthetic pyrethroid insecticide widely used to control pests in various crops, such as cotton, cereals, potatoes, vegetables, and fruits. It acts primarily through contact and ingestion, being effective against a wide range of insects, including aphids, thrips, Colorado potato beetles, caterpillars, mosquitoes, and mites.

Common name (ISO): lambda-cyhalothrin (lambda-cyhalothrin)

Synonyms: PP 321, WHO 3021, Karate (commercial product name)

Gross chemical formula: C23H19ClF3NO3

Number CAS: 91465-08-6

Chemical class: Synthetic pyrethroid (class of pyrethroid esters, derived from halogenated cyclopropanecarboxylic acids).

Release year: 1985

Development history: Lambda-cyhalothrin was developed between 1974 and 1977 by chemists at Imperial Chemical Industries (ICI, later Zeneca) at the Jealott's Hill research center in the United Kingdom, as patentable analogues of existing pyrethroids – such as permethrin, cypermethrin, and deltamethrin. The key innovation involved replacing a chlorine atom with a trifluoromethyl group in the side chain, increasing insecticidal potency (up to 10 times more active) and UV light stability, as well as improving its action against mites. Initially, it was produced as cyhalothrin (brand name Grenade), a mixture of four isomers. Later, it was refined to lambda-cyhalothrin (code PP321), a 1:1 mixture of two enantiomers (RS and SR), more biologically active, via crystallization processes and recycling of unwanted isomers. Commercial synthesis is complex, involving esterification, halogenation, and stereoselective cyclopropanation with fluorinated and chlorinated reagents. In 2000, Zeneca merged with Novartis to form Syngenta, which remains the main manufacturer.

Mode of action: This non-systemic insecticide acts through contact and stomach ingestion, possessing repellent properties. It is a sodium channel modulator (IRAC class 3A), acting as a fast-acting axonal excitotoxin: it interferes with the nervous system of insects, preventing the closure of voltage-dependent sodium channels in axonal membranes. This keeps the channels open, inhibiting nerve repolarization, causing hyperexcitation, paralysis, and death. It provides rapid knockdown, ceasing feeding and causing the affected insects to fall.

Patent numbers: US 4183948, GB 2085000, EP 1578720 and others.

Other technical information:

The study assessed the fitness of a population of Eriopis connexa (Germar) resistant to lambda-cyhalothrin in relation to development, reproduction, survival under prey scarcity, and prey consumption. [...] The results obtained show that resistant females have lower reproductive output than susceptible females and that this is not related to the knockdown effect; however, the costs of recovery from knockdown interfere with offspring survival and also, to a lesser extent, with prey consumption. Thus, we conclude that the population of Eriopis connexa Resistant to lambda-cyhalothrin exhibits a disadvantage in egg production compared to susceptible populations, and this disadvantage increases when the population is subjected to prey scarcity. - DOI 10.1111/j.1461-9563.2012.00599.x -

The transmission rate of the virus by two genotypes of Myzus persicaeThe study evaluated the interaction of aphid vectors, fed with potato leaves infected with potato virus Y (PVY) and treated with the pyrethroid lambda-cyhalothrin. [...] Lambda-cyhalothrin, in commercial formulation, interrupts PVY transmission by disorienting the aphid vectors long enough for the virus to lose its transmissibility. However, the genotypes of Myzus persicae Individuals carrying the M918L mutation are not prevented from transmitting the virus. DOI 10.1002/ps.3967