Insecticides, Fungicides, and Herbicides all fall under the category of pesticides with pests being described as any living organism that is present in a place where it is not wanted and this can be in the form of insects, mammals(rodents), weeds, and microbes just to mention a few. This paper will look at the organic composition of these pesticides, the small differences between them and present that for people to see. Pesticides are categorized according to chemical composition; insecticides, fungicides, herbicides, and bactericides, as shown in.
Herbicides are used to kill off weeds or to reduce and contain their growth. These pesticides are utilized in different tasks such as forestry, pasture, maintenance, and control of wildlife habitats among other uses. Fungicides function to inhibit the growth of fungi and fungal spores or to treat damage caused by the same. Such pesticides are used in agriculture and livestock to fight against fungal infections. An insecticide refers to a class of pesticides used against insects ( Geissbühler & Kearney , 2013). The various chemical components of these pesticides are often the same with only small variations that aim to change the intended effect of the resulting compound. The major chemical components of pesticides include organophosphates, carbamates, pyrethroids and organochlorides. Organophosphates, which are organic esters of phosphoric acid, form the basis of many insecticides and also herbicides. They contain a number of different groups bonded to the phosphorous; terminal oxygen connected via a double bond, two lipophilic groups and a leaving group, often a halide ( Gupta, 2011). Examples of organophosphates include chlorethoxyfos, chlorpyrifos, coumaphos , diazinon and malathion which is among the most widely used in the United States. Organophosphate pesticides (OPPs), function by inhibiting a neuromuscular enzyme necessary for normal body function in insects ( Griffiths, 2012). Carbamates are derivatives of carbamic acid and are used as insecticides to kill insects. Examples include aldicarb, carbofuran (Furadan), carbaryl (Sevin), and methomyl. Carbamates kill insects through a reversible inactivation of the enzyme acetyl cholinesterase while organophosphate pesticides also act on the same enzyme but irreversibly causing more damage than carbamates ( Vargas, Rodríguez & Herrera, 2012).
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Pyrethroids form the most common insecticides for commercial household use. Pyrethroids are usually not harmful to humans when used in small doses although people with allergies or extra sensitivity may be affected by their use. Examples of pyrethroids include allethrin, cyfluthrin, cyphenothrin, esfenvalerate, fenpropathrin, permethrin, tetramethrin, and transfluthrin ( Matsuo & Mori, 2012).
Fungicides function by interfering with critical cellular processes of fungi e.g. Some bind with specific enzymes to interrupt the metabolic pathways involved with cellular respiration. Strobilurin compounds are highly used in industrial agriculture to deal with various types of mildews and molds. Other substances occasionally used as fungicides include methyl bromide, and formaldehyde, although their use has either been banned or is highly controlled in most countries.
There are various types of fungicides based on their use and also method of application. Agricultural or horticultural fungicides are usually applied as sprays as this allows the application to be done in large scale over farms. Seed fungicides usually have to be applied on the seed as a protective covering even before germination. This prevents the seed from being attacked by fungi while still in the ground before germination ( Singh 2014). Chemotherapeutants, also known as systemic fungicides, are applied to the actual plant which then distributes the fungicide into the plant tissues to either eradicate or prevent fungal infections. Pharmaceutical fungicides are used on humans and animals and are commonly applied on the skin in form of topical antifungal creams. They can also be in the form of oral medications ( Oliver & Hewitt, 2014). The use of insecticides, herbicides and fungicides will continue to evolve as more and more compounds are discovered and synthesized and the challenge for man will remain on finding a way to ensure that these chemical compounds being used on the earth do not find their way into the human food chain but incase they do, their effect is relatively low.
References
Geissbühler H., Kearney P. (2013). Synthesis of Pesticides Chemical Structure and Biological Activity Natural Products with Biological Activity: Symposia Papers Presented at the Fourth International Congress of Pesticide Chemistry, Zurich, Switzerland, July 24-28, 1978 . Elsevier,
Griffiths G. (2012). Fine Structure Immunocytochemistry. Springer Science & Business Media,
Gupta, Ramesh. (2011). Toxicology of Organophosphate and Carbamate Compounds. Academic Press,
Matsuo N., Mori T. (2012). Pyrethroids: From Chrysanthemum to Modern Industrial Insecticide . Springer Science & Business Media
McMurry J. (2015). Organic Chemistry. Cengage Learning
Oliver R., & Hewitt G. (2014). Fungicides in Crop Protection, 2nd Edition, CABI.
Singh D. (2014). Advances in Plant Biopesticides . Springer
Vargas, R., Rodríguez, E., Herrera G. (2012). Evolution and Expectations of Enzymatic Biosensors for Pesticides . 329-356. 10.5772/46227.
