May 21, 2024

Pyrethroids: Advancements in Formulations and Applications for Effective Insect Management

Pyrethroids are modern-day synthetic pesticides derived from the chemical structure of natural pyrethrins which are found in chrysanthemum flowers. Synthesized during the 1970s, pyrethroids have revolutionized insect control due to their low mammalian toxicity and high-potency against insects. They are widely used globally in applications ranging from agriculture to mosquito control to household insecticides. This article discusses the classification, uses, toxicity and impacts of pyrethroids.

Classification of pyrethroids

Based on their chemical structure, pyrethroids are classified into two major types:

– Type I or Type II pyrethroids: Type I pyrethroids are more toxic to insects but less toxic to mammals. Permethrin and Tetramethrin are examples.

– Type II pyrethroids: These are less toxic to insects but more toxic to mammals compared to Type I. Deltamethrin and Cypermethrin are common Type II pyrethroids.

Some newer pyrethroids have properties of both Type I and II and are classified as Type I/II or mixed pyrethroids like Esfenvalerate. Proper classification helps understand their toxicity profile and select the right product.

Uses of pyrethroids in agriculture
Pyrethroids are extensively used globally in agricultural applications due to their high efficiency against a broad range of insect pests like aphids, moths and flies. Some major uses are:

– Crops protection: Pyrethroids protect valuable crops from devastating insect damages. For example, Fenpropathrin protects cotton, Fructopyran and Fenvalerate protects fruits and vegetables.

– Livestock pest control: Ectoparasites like lice and ticks that infect livestock are effectively killed by pyrethroid pour-ons and sprays. Deltamethrin and Cypermethrin are commonly used.

– Public health pest control: Mosquitoes spreading diseases like malaria, dengue, Zika are targeted. Fenitrothion and Sumithrin are used in fogging, indoor residual spray programs.

– Stored grain protection: Pyrethroids prevent worm infestations in stored rice, wheat and protect significant food supplies. Deltamethrin and Lambda-cyhalothrin are frequently used.

Pyrethroids in public health and home insect control

Beyond agriculture, pyrethroids are vital for public health due to their safety and low resistance in disease vectors. Major uses are:

– Treated bednets: Long-lasting insecticidal nets (LLINs) treated with pyrethroids save millions from malaria. Alpha-cypermethrin and Deltamethrin are commonly used.

– Indoor residual spray (IRS): IRS with pyrethroids inside homes/buildings effectively reduce disease transmission. K-Othrine/Deltamethrin mixtures are popular choices for IRS programs.

– Mosquito control: Space spraying during outbreaks, fogging in residential areas effectively reduce mosquito populations. Sumithrin and Fenitrothion mixtures are widely used.

– Home insect control: Raid, Baygon and other household insecticides readily available for home users control cockroaches, ants with formulations of Cypermethrin, Phenothrin or D-Phenothrin.

Toxicity of Pyrethroids

While significantly safer than older pesticides, concerns remain over potential toxicity especially through repeated/high exposures:

– Neurotoxicity: Pyrethroids primarily target the nervous system in insects and mammals. Symptoms include tremors, increased salivation in high doses.

– Developmental/reproductive effects: Studies link permethrin and cypermethrin to impaired fertility, birth defects, neurodevelopmental issues at high doses in animal trials.

– Allergic reactions: Skin rashes, itching and breathing issues occur occasionally due to sensitivity/allergic reactions to some pyrethroids.

– Cancer risk: The EPA classifies likely carcinogens like cypermethrin as probable carcinogens based on animal test tumors, but human evidence is limited.

Therefore, relevant authorities emphasize judicious use following guidelines and taking precautionary measures like using mosquito nets, protective clothing, and discarding containers as hazardous waste to prevent contamination.

Environmental impacts and resistance

Like all pesticides, improper use of pyrethroids pollutes the environment and increases insect resistance risks:

– Pollution of soil & waterways: Overspray drift deposition in non-target sites pollutes the environment. Pyrethroids persist and accumulate in sediments.

– Toxicity to aquatic life: Highly toxic to fish and aquatic insects even at low doses. Permethrin is suspected to damage reproductive/developmental processes in fish.

– Decimation of non-target organisms: Beneficial insects pollinators, parasites that naturally keep pests in check are unintentionally killed by pyrethroids.

– Insect resistance: Over-reliance and misuse has led to development of resistance in disease vectors and crop pests to commonly used pyrethroids worldwide requiring replacement.

Therefore, integrated pest management with other methods and judicious targeted use as one component is recommended to preserve this important class of chemicals. Proper disposal helps prevent environmental damage.

1.Source: Coherent Market Insights, Public sources, Desk research
2.We have leveraged AI tools to mine information and compile it