Propesticides and Their Implications (original) (raw)
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the complex mix of chemical pesticides with a variety of central atoms and a large variety of substituents around them acts in different manner with the targeted living species. The mechanism of this interaction forms the basis of their toxicity. This chapter is intended to describe the chemistry of a few selected chemical classes of pesticides with the purpose of illustration of the mechanism of their interaction with the targeted living species and the impact that their usage has on the ecology including the living environment. The organochlorines, organophosphates, carbamates, pyrethroids, phenoxys, thiocarbamates, and triazines are the important 14 classes of pesticides dicussed here. They form 70% of those that have been and are still in use. The pesticide classes not discussed here include the amides, benzimidazole, benzonitrile, botanicals, dinitroanilines, phthalates, and triazoles. The characteristics of the various pesticides described here are readily available on several websites, important among them being basic guides, carsoncouncil, EXTONET and PANNA.
Pesticide toxicity: a mechanistic approach
EXCLI Journal, 2018
Pesticides are known for their high persistence and pervasiveness in the environment, and along with products of their biotransformation, they may remain in and interact with the environment and living organisms in multiple ways, according to their nature and chemical structure, dose and targets. In this review, the classifications of pesticides based on their nature, use, physical state, pathophysiological effects, and sources are discussed. The effects of these xenobiotics on the environment, their biotransformation in terms of bioaccumulation are highlighted with special focus on the molecular mechanisms deciphered to date. Basing on targeted organisms, most pesticides are classified as herbicides, fungicides, and insecticides. Herbicides are known as growth regulators, seedling growth inhibitors, photosynthesis inhibitors, inhibitors of amino acid and lipid biosynthesis, cell membrane disrupters, and pigment biosynthesis inhibitors, whereas fungicides include inhibitors of ergos...
Biochemical and Biophysical Research Communications, 2009
We report the isolation of a Pseudomonas sp. which is able to transform imidacloprid and thiamethoxam under microaerophilic conditions in the presence of an alternate carbon source. This bacterium, Pseudomonas sp. 1G, was isolated from soil with a history of repeated exposure to imidacloprid. Both insecticides were transformed to nitrosoguanidine (@NANO), desnitro (@NH), and urea (@O) metabolites and a transformation pathway is proposed. This is the first conclusive report of bacterial transformation of the 'magic nitro' group which is responsible for the insect selectivity of neonicotinoid insecticides. Crown
2019
Pesticides are known for their high persistence and pervasiveness in the environment, and along with products of their biotransformation, they may remain in and interact with the environment and living organisms in multiple ways, according to their nature and chemical structure, dose and targets. In this review, the classifications of pesticides based on their nature, use, physical state, pathophysiological effects, and sources are discussed. The effects of these xenobiotics on the environment, their biotransformation in terms of bioaccumulation are highlighted with special focus on the molecular mechanisms deciphered to date. Basing on targeted organisms, most pesticides are classified as herbicides, fungicides, and insecticides. Herbicides are known as growth regulators, seedling growth inhibitors, photosynthesis inhibitors, inhibitors of amino acid and lipid biosynthesis, cell membrane disrupters, and pigment biosynthesis inhibitors, whereas fungicides include inhibitors of ergos...
TOXICOLOGICAL STUDIES OF SOME PESTICIDES IN RELATION TO THEIR SIDE EFFECTS
The study aimed to evaluate the insecticidal activity of eight organophosphate and carbamate insecticides against certain pests commonly attacking vegetable plants. The pests included sucking pests (i. e. aphids, whitefly, mites) and the cotton leafworm Spodoptera littoralis. In this respect laboratory and field experiments (at fields grown with squash and okra) were carried out. In addition, the toxicity these pesticides to the predator, paederus alferii in the laboratory was studied. The tested organophosphorus were chloropyrifos-methyl, dimethoate, phenthoate, profenofos and pirimiphos-methyl while those of carbamates were, carbosulfan, primicarb and propoxur. The most efficient insecticides (i. e. chloropyrifos-methyl and pirimicarb) were further evaluated for their mammalian toxicity against white albino rats. So, acute and subchronic studies were conducted. In subchronic studies rats were orally given the insecticides at doses 1/ 10 and 1/30 LD50 for each insecticide. The treatmen...
Insecticides with novel modes of action: Mechanism, selectivity and cross-resistance
Entomological Research, 2007
Efforts have been made during the past two decades to develop insecticides with selective properties that act specifically on biochemical sites present in particular insect groups, but whose properties differ from other insecticides. This approach has led to the discovery of compounds that affect the hormonal regulation of molting and developmental processes in insects; for example, ecdysone agonists, juvenile hormone mimics and chitin synthesis inhibitors. In addition, compounds that selectively interact with the insect nicotinic acetylcholine receptor, such as imidacloprid, acetamiprid and thiamethoxam, have been introduced for the control of aphids, whiteflies and other insect species. Natural products acting selectively on insect pests, such as avermectins, spinosad and azadirachtin, have been introduced for controlling selected groups of insect pests. Compounds acting on the nervous site that controls the sucking pump of aphids and whiteflies, such as pymetrozine, or respiration, such as diafenthiuron, have been introduced for controlling sucking pests. All the above compounds are important components in pest and resistance management programs.
Pesticides of Botanical Origin: a Promising Tool in Plant Protection
Pesticides - Formulations, Effects, Fate, 2011
Future agricultural and rural development is, to a large extent, influenced by the rapidly increasing food demand of 2.5 billion people expected to swell the world population by 2020. Achieving food sufficiency in a sustainable manner is a major challenge for farmers, agro-industries, researchers and governments (Schillhorn van Veen, 1999). The intensification of agriculture to fulfil food needs has increased the number of insect pest species attacking different crops and as a result the annual production losses of the standing crops. In the past, synthetic pesticides have played a major role in crop protection programmes and have immensely benefited mankind. Nevertheless, their indiscriminate use has resulted in the development of resistance by pests (insects,weeds, etc), resurgence and outbreak of new pests, toxicity to non-target organisms and hazardous effects on the environment endangering the sustainability of ecosystems (Jeyasankar & Jesudasan, 2005). In the recent years the EU has employed a fundamental reform of the Common Agricultural Policy (CAP) highlighting the respect to the environmental, food safety and animal welfare standards, imposing farmlands' cross-compliance with good agricultural and environmental conditions (Schillhorn van Veen, 1999). Due to environmental side effects and health concerns, many synthetic carbamate, organophosphate, and organophthalide pesticides have been banned (Council Directive 91/414/EEC) or are being under evaluation (Regulation 2009/1107/EC OL & Directive 2009/128/EC). On the other hand, industry does not equally sustain the economic cost of research and registration, of all pesticides' chemical classes. The development of nematicides is rarely supported, even though in some cases, such as in the Netherlands, they represent more than 60% of the total pesticides used in agriculture (Chitwood, 2002). This is due to the fact that nematodes are a rather difficult target and the economic cost of research and registration is an enormous hurdle for a prospective new synthetic nematicide to overcome (Chitwood, 2002). As a result, currently there are only few nematicides left in use, and their limited number makes the repeated applications of the same formulation, inevitable. This fact has led to the enhancement nematicides biodegradation in soil (Qui et al., 2004 , Karpouzas et al., 2004, Arbeli & Fuentes, 2007) and the development of resistance in pests. (Meher et al., 2009) These two phenomena are expressed in field as lack of efficacy of the applied pesticides. All the above facts necessitate the urge for new and alternative pest control methods (Chitwood, 2002). An interesting way of searching for biorational pesticides is screening naturally occurring compounds in plants (Isman, 2006; 2008). Plants, as long-lived stationary organisms, must www.intechopen.com Pesticides-Formulations, Effects, Fate 4 resist attackers over their lifetime, so they produce and exude constituents of the secondary metabolism (PSMs), playing an important role in their defence mechanisms. In fact, the phytochemicals' research has its roots in allelochemistry, involving the complex chemicalmediated interactions between a plant and other organisms in its environment (Chitwood, 2002). Among the 500,000 estimated PSMs only 18,000 have been characterised up until 2008. The main groups of PSMs are (i) phenylpropanoids and phenolics, (ii) terpenoids and steroids, (iii) alkaloids and nitrogen compounds. PSMs were used in plant protection from the end of 19th century till the beginning of the Second World War, when synthetic organic pesticides took over. The development of botanicals used as pesticides resulted from two parallel methods: I) the observation of the traditional uses of plants and extracts for cattle and crop protection, followed by checking the efficiency of these practices and identification of the active molecules. The activity of nicotine extracted from tobacco (Nicotiana tabacum) and rotenone from Fabaceae Lonchocarpus nicou and Derris elliptica fall in this category; II) the systematic screening of botanical families followed by biological tests in order to discover the active molecules. Ryanodine, an alkaloid extracted from Ryania. sp., and marketed in the United States in 1945, is the result of such prospecting, carried out with a collaboration between Rutgers University and Merck in the early 1940s. Before the Second World War, four main groups of PSMs were used in pest management: nicotine and alkaloids, rotenone and rotenoids, pyrethrum and pyrethrins, and vegetable oils. The commercialization of synthetic pesticides including organochlorides, organophosphates, and carbamates, followed. Research on biopesticides of plant origin was actively pursued again throughout the second half of the 20th century in order to improve their stability or to discover new molecules and new sources of molecules. The development of pyrethrinoids, synthetic molecules analogous to pyrethrum, and neem products (Meliaceae) are characteristic examples of commercial plant protection products based on botanical sources. Botanicals and plant allelochemicals are clearly defined as semiochemicals by Organization for Economic Cooperation and Development (OECD). This definition includes all chemicals involved in species communication (pheromones, but also plant extracts, plant volatiles, and natural oils) and exhibiting pest control activities. The concept of biocontrol agents (BCAs) has recently been preferred to that of biopesticides (Regnault-Roger & Philogène, 2008). PSMs may have applications in weed and pest management, if developed for use as pesticides themselves, or they can be used as model compounds for the development of chemically synthesized derivatives. Many of them are environmentally friendly, pose less risk to humans and animals, have a selective mode of action, avoid the emergence of resistant races of pest species, and as a result they can be safely used in Integrated Pest Management (IPM) (Isman, 2006). Furthermore, they may be proved suitable and be used as products of choice for organic food production. Extensive is the literature concerning the use of plants' crude or refined extracts in various fields of crop protection (insects, fungi, nematodes, bacteria, weeds). It is mandatory though to attribute the efficacy of botanicals to specific identified constituent compound(s) in order to delineate the mechanisms of bioactivity, biologically and biochemically, and to fully exploit the therapeutic potential of extracts (Akhtar & Mahmood, 1994). This is a short review encompassing the main chemical classes of PSMs that have been used in crop protection focusing on the most recent advances in the chemicals disclosed, their mode of action and their fate in the ecosystem. In addition, we present our research group's findings on biological activities of limonoids and terpenes, representing our step forward to the contribution in this scientific topic. Finally, we examine
Insecticides with Novel Modes of Action: An Overview
Conventional insecticides such as chlorinated hydrocarbons, organophosphates, carbamates and pyrethroids were successful in controlling insect pests during the past five decades, minimizing thereby losses in agricultural yields. Unfortunately, many of these chemicals are harmful to man and beneficial organisms and cause ecological disturbances. Although considerable efforts have been made to minimize the adverse environmental impact of pesticides and to maximize food production and health of the human population and domestic animals, there is today a great demand for safer and more selective insecticides affecting specifically harmful pests, while sparing beneficial insect species and other organisms. Furthermore, the rapidly developing resistance to conventional insecticides provides the impetus to study new alternatives and more ecologically acceptable methods of insect control as part of integrated pest management (IPM) programs.
Chemosensors
Pesticides are commonly used in agriculture and are an important factor of food security for humankind. However, the overuse of pesticides can harm non-target organisms, and, thus, it is vital to comprehensively study their effects on the different metabolic pathways of living organisms. In the present study, enzyme-inhibition-based assays have been used to investigate the effects of commercial pesticide formulations on the key enzymes of the organisms, which catalyze a wide variety of metabolic reactions (protein catabolism, lactic acid fermentation, alcohol metabolism, the conduction of nerve impulses, etc.). Assay conditions have been optimized, and the limitations of the methods used in the study, which are related to the choice of the solvent for commercial pesticide formulations and optical effects occurring when commercial pesticide formulations are mixed with solutions of enzymes and substrates of assay systems, have been revealed. The effects of commercial pesticide formula...