Insecticides in agriculture

The increased use of IV-methyl carbamate insecticides in agriculture demands the development of selective and sensitive analytical procedures to determine trace level residues of these compounds in crops and other food products. HPLC is the technique most widely used to circumvent heat sensitivity of these pesticides. However, HPLC with UV detection lacks the selectivity and sensitivity needed for their analysis. In the late 1970s and early 1980s, HPLC using post-column hydrolysis and derivatization was developed and refined with fluorescence detection to overcome these problems. The technique relies on the post-column hydrolysis of the carbamate moiety to methylamine with subsequent derivatization to a fluorescent isoindole product. This technique is currently the most widely used HPLC method for the determination of carbamates in water" and in fruits and vegetables." " ... 

HCH insecticide in agricultural areas of the Mugano-Salyansk land region and also loss or leaching of its residues from recently formed RPA (Galiulin and Galiulina, 1996). Meanwhile the proportion of DDT in the bottom sediments of rivers was DDE + DDD/DDT < 1, that may indicate a relatively little transformation of this insecticide in the present environment (Galiulin, 1994). 

The main polysulphide products are trisulphide, tetrasulphide and pentasulphide, but on account of the tendency of the polysulphides to decompose, yielding thiosulj hate and hydrogen sulphide, the quantity of thiosulphate usually exceeds that indicated in the equation.7 Loss of sulphur by the thiosulphate yields sulphite.8 The so-called lime-sulphur washes, used as insecticides in agricultural work, are obtained by treating sulphur with milk of lime in this way.9... 

There are hundreds of organophosphorus and carbamate insecticides in agricultural and household use. Two important examples are malathion, an organophosphorus compound, and carbaryl, a carbamate, both shown in Figure 15.20. Malathion kills a variety of insects, such as aphids, leafhoppers, beetles, and spider mites. Carbaryl, like many other carbamates, is relatively selective in the types of insects it kills. 

Nicotine (C10 H14 N2, beta-pyridyl-alpha-N methylpyrrolidine) is a very poisonous, water- and lipid-soluble, liquid alkaloid with a burning taste. It is colorless, but turns brown and takes on the odor of tobacco upon exposure to air. First isolated in 1828, it is used as an insecticide in agriculture, and as a killer of parasites in veterinary medicine. 

Uses Phosphamidon is used as a broad-spectrum insecticide in agriculture. It is toxic both systemically and by contact, and acts through the inhibition of ChE. Phosphamidon currently is registered for use by both ground and aerial applications on vegetables, fruits, and field crops.28... 

Many natural products and biologically active compounds contain cyclopropane rings we shall feature j ist a few. First, a most important natural insecticide, a pyrethrin from the East African pyrethrum daisy, and its synthetic analogue decamethrin, now the most important insecticide in agriculture (see Chapter 1). Very low doses of this highly active and nonpersistent insecticide are needed. 

A broad spectrum insecticide in agricultural applications. When heated to decomposition it emits highly toxic fumes of NOx, POx, and SOx. 

Pyrethrin I (the chapter-opening molecule) and decamethrin both contain cyclopropane rings. Pyrethrin I is a naturally occurring insecticide obtained from chiysanthemums, whereas deca-methrin is a more potent synthetic analogue that is widely used as an insecticide in agriculture. 

Both the naturally occurring pyrethrins and the synthetic pyrethroids are widely used as insecticides in agricultural, public health, and domestic applications. They are also used as ectoparisiticides in veterinary and human medicine. Attractive features are their low environmental persistence, and their rapid knock down activity, whereby flying insects very quickly become uncoordinated and unable to fly before they are killed. 

A typical example of replacing the products is the fairly recent production of bioinsecticides instead of the production of chemical insecticides. In agriculture, the replacement of powdered fertilizers (causing many problems during their application into the soil) by liquid fertilizers is also important. 

Anticholinesterase compounds constitute the largest number of chemicals that are primarily used as insecticides in agriculture, industry, and around the home/garden. Some OPs (nerve agents) have been used both in chemical warfare and terrorist attacks while other OPs and CMs have been recommended as therapeutic agents in human and veterinary medicine. 

Despite its high toxicity, nicotine was used as an insecticide in agriculture, since there were hardly any compounds with higher selectivity. Around 1950, the world s annual demand for nicotine came to around 2,800 tonnes. 

Tobacco is derived from the leaves of Nicotiana tabacum (Solanaceae), and it was used to treat headache and toothache. However, it is not used as a medicine now, and smoking tobacco is now a global addictive habit. Tobacco leaf contains a large amount of nicotine (2-8%), and the nicotine extracted as nicotine sulfate is used as an insecticide in agriculture. Tobacco leaf contains more than ten related alkaloids other than nicotine, and all of these alkaloids possess a pyridine skeleton with 3-substitution. The main alkaloids other than nicotine, anabasine and nor-nicotine, are isolated from the leaf material, and these alkaloids also possess insecticidal activity. 

Amason JT (2011) Natural products from plants as insecticides in agriculture and human health (Chapter 13). In Pezzuto JM, Kato MJ (eds) Photochemistry and pharmacognosy. Encyclopedia of life support systems (EOLSS), developed under the Auspices of the UNESCO. Eolss, Oxford... 

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