Systemic insecticides, activity

There is a great deal of activity in the synthesis of 2,2-dimethylbenzofm-ans such as Carbofuran (179). Carbofuran is a systemic insecticide active against flies, aphids, larvae, and mosquitos. 

IKI-1145 is a new phosphoramidothioate insecticide and nematicide discovered by Ishihara Sangyo Kaisha, Ltd. It is characterized by an excellent nematicidal activity and an marked systemic insecticidal activity. It also shows high activity against pests having resistance to conventional insecticides. These properties can be considered very attractive for the control of nematodes and foliar pests. 

Me0>2P(0)0CMe = CHC02Me. A trade name for a highly active systemic insecticide both CIS and trans isomers are active. 

Carbamate Insecticides. These are stmcturaUy optimi2ed derivatives of the unique plant alkaloid physostigmine [57-47-6] a cholinergic dmg isolated in 1864 from Phjsostigma venenosum (see Alkaloids) (17,24,35—39). The carbamates maybe considered synthetic derivatives of the synaptic neurotransmitter acetylcholine, with very low turnover numbers. The A/,A/-dimethylcarbamates of heterocycHc enols (36) and the Ai-methylcarbamates of a variety of substituted phenols (35) with a wide range of insecticidal activity were described in 1954 (35). The latter are the most widely used carbamate insecticides, and the A/-methylcatbamates of oximes have subsequentiy been found to be effective systemic insecticides. 

Toxification rates may vary. For example, when humans are acutely poisoned by the systemic insecticide menazon, there is an incubation period (of up to one day) and a slow growth in the anticholinesterase activity when the PS-form with low toxicity becomes the active PO-form [A17]. 

Verona and Picci (U9) have shown that the phosphorus contained in Hanane was used by the soil microbes for their nutrition in relation with studies conducted on the breakdown of systemic insecticides. Pianka, as cited by Nicol (32), has reported that it is possible to enhance the activity of systemic insecticides by the addition of certain chemicals not necessarily systemic. Samples of dimefox activated by... 

We have recently reported ( ) several synthetic studies of weak nucleophile SnAr reactions. In the latter cases (26f-1), new synthetic methodology was reported for the direct introduction of fluoroalkoxy groups into a variety of aromatic systems. These reports represent synthetically useful procedures for obtaining some otherwise inaccessible fluoroalkoxy materials but, unfortunately, they require the use of a dipolar, aprotic solvent (usually hexamethylphosphoramide, HMPA) and, in some cases, elevated temperatures. However, because of their diverse and important applications ( ), the syntheses of these and other organofluoro compounds continue to be of interest. For example, two recent reports of useful fluoroalkoxy materials include the insecticide activity exhibited by fluoroalkoxy substituted 1,3,4-oxadiazoles... 

The activity spectrum of a pesticidal compound is often determined by the physical properties of the compound. For example, systemic insecticides usually require both water and lipid solubility since it is necessary for them to pass through... 

Pyrethrinoids are powerful natural insecticides that act on the nervous system of insects. They are esters of chrysantemic acid with a substituted cyclopentenol. The replacement of this motif by a more photochemically stable group affords products that are utilizable in agrochemistry. These compounds exhibit a high insecticide activity and are nontoxic for mammals consequently, they are established in very important markets (e.g., deltamethrin, permethriri). Some fluorinated pyrethrinoids have been synthesized and marketed. One goal of these compounds is to enhance the acaricide activity. Some examples are given in Figure 4.46. 

Lindane, the y-isomer of HCH, is a potent insecticide. Its insecticidal action is due to a hyperexcitatory effect on the insect s central nervous system induced by accumulation of acetylcholine in the synaptic region 73). We prepared a number of analogs in which some of the chlorine atoms are replaced by other substituents while maintaining the -configuration and determined their insecticidal activity against mosquitos74,). 

The tobacco compound nicotine has been used as an insecticide for over 200 years. It is especially effective against sucking insects, such as aphids, and has excellent contact activity. Related compounds are neonicotinoids (e.g., imidacloprid), which have similar insecticidal activity, but are less toxic to mammals. Nicotine and imidacloprid mimic the action of acetylcholine, which is the major excitatory neurotransmitter in an insect s central nervous system. The action of acetylcholine is stopped by the enzyme acetylcholinesterase, which rapidly breaks down acetylcholine. Nicotine and imidacloprid are also neuroexcitatory, but do so persistendy, since they are not affected by acetylcholinesterase. Overstimulation of the nervous system often leads to convulsions, paralysis, and death. 

The A/-phenylpyrazole insecticide fipronil, already discussed in Section 2.1.1.2, contains the unusual trifluoromethylsulfinyl substituent, not often seen in agrochemical chemistry. Following the introduction of fipronil, several chemistries related to fipronil were launched, including acetoprole [105], an insecticide with acaricidal and nematicidal activity, and ethiprole [106], a systemic insecticide for the control of a broad spectrum of insects, both from Bayer CropScience. 

Systemic insecticide with translaminar activity and with contact and stomach action... 

Insecticide active by ingestion and contact also exhibits root systemic activity... 

Systemic, ingested insecticide active by root application. Interferes with moulting affecting larval stages of insects. Also reduces fecundity in treated adults and have some ovicidal properties... 

Systemic insecticide with translaminar activity and with contact and stomach action. Readily taken up by plant and further distributed acropetally, with good root-systemic action... 

Dimethoate is a systemic insecticide and acaricide with contact and stomach poison activity for control of a wide range of insects such as aphids, leafhoppers, thrips, white-flies, and mites in apples, corn, cotton, citrus, ornamentals, vegetables, and others. It has an oral LD50 in rats of 235 mg/kg. 

Imidacloprid is a systemic insecticide with contact and stomach poison activity for control of sucking insects including aphids, leafhoppers, planthoppers, thrips, and whiteflies, and soil insects, termites, and some species of biting insects. It has an oral LD30 in rats of 450 mg/kg. 

Lufenuron is a benzoylurea compound with chitin synthetase inhibitory activity that is used principally as a systemic insecticide. Given orally to horses, at a dose rate of 5 mg/kg once daily, lufenuron may be beneficial when used in combination with topical antifungal agents. The potential toxicity of this compound in the horse has not been investigated. 

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