Insecticidal activities

These compounds were tested against a series of Lepidoptera including Plutella xylostella Px, diamondback moth), Hdiothis virescens Hv, tobacco budworm), and Spodopterafrugiperda (Sf, fall armyworm). Insecticidal activity is reported in Tables I-111 as percent plant protection at various concentrations where reduction in plant damage generally resulted from insect mortality rather than cessation of feeding. 

Compounds of formula 15 where Rj is isopropyl or butyl, R2 is haloalkyl (i.e., trifluoroethyl, difluoromethyl or bromodifluoromethyl), Rj is chlorine or bromine 

In Table III, percent plant protection is reported for phenyl and pyridylpyrimi-dine anthranilic diamides of formula 19 against lepidopteran pests. A similar trend in structure-activity was observed for substitution on 19 as that for arylpyrazole anthranilic diamides 12 and 15. Pyridylpyrimidine diamide 4 (formula 19 where Rj is isopropyl, Rj is chlorine and X is N) provided the highest level of plant protection with activity approaching that of more active pyridylpyrazoles diamides of formula 

However, arylpyrimidine diamides 19 tended to be less active overall than the corresponding arylpyrazole derivatives 15. 

The discovery of a novel class of anthranilic diamide insecticides having exceptional activity against a broad spectrum of Lepidoptera at extremely low rates of application has successfully led to the commercialization of Rynaxypyr (2). Compounds of this chemistry class exert their effect by causing release of intracellular Ca stores in muscle cells by activation of the ryanodine receptor. As a new mode-of-action product with outstanding insecticidal properties, Rynaxypyr offers great promise for the marketplace. 

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Aldrin is insecticidally active as a contact and stomach poison against a wide range of soil pests. It is non-phytotoxic and does not cause taint. Aldrin is toxic to humans and animals and is now less used. 

Pyrethroids from Chiysanthemic Acid. The unsaturated side chains of the aHethrolone alcohol moieties of the natural pyrethrins are readily epoxidized by microsomal oxidases and converted to diols, thus detoxifying the insecticides. Esterification of chrysanthemic acid (9), R = CH3, with substituted ben2yl alcohols produces usehil insecticides barthrin [70-43-9J, 2-chloro-3,4-methylenedioxyben2yl (+)-i7j ,/n7 j -chrysanthemate, and dimethrin [70-38-2] 2,4-dimethylben2yl (+)-i7j ,/n7 j -chrysanthemate. These have alimited spectmm of insecticidal activity but are of very low mammalian toxicity, ie, rat oralLD s >20,000 mg/kg. 

Cyclodienes. These are polychlorinated cycHc hydrocarbons with endomethylene-bridged stmctures, prepared by the Diels-Alder diene reaction. The development of these insecticides resulted from the discovery in 1945 of chlordane, the chlorinated adduct of hexachlorocyclopentadiene and cyclopentadiene (qv). The addition of two Cl atoms across the double bond of the ftve-membered ring forms the two isomers of chlordane [12789-03-6] or l,2,4,5,6,7,8,8-octachloro-2,3,3t ,4,7,7t -hexahydro-4,7-methano-lJT-indene, QL-trans (mp 106.5°C) and pt-tis (32) (mp 104.5°C). The p-isomerhas signiftcantiy greater insecticidal activity. Technical chlordane is an amber Hquid (bp 175°C/267 Pa, vp 1.3 mPa at 25°C) which is soluble in water to about 9 fig/L. It has rat LD qS of 335, 430 (oral) and 840, 690 (dermal) mg/kg. Technical chlordane contains about 60% of the isomers and 10—20% of heptachlor. It has been used extensively as a soil insecticide for termite control and as a household insecticide. 

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. 

The polyether antibiotics exhibit a broad range of biological, antibacterial, antifungal, antiviral, anticoccidial, antiparasitic, and insecticidal activities. They improve feed efficiency and growth performance in mminant and monogastric animals. Only the anticoccidial activity in poultry and catde, and the effect on feed efficiency in mminants such as catde and sheep are of commercial interest. 

Methicillin — see Penicillin, 2,6-dimethoxyphenyl-Methidathion insecticidal activity, 6, 576 as insecticide, 1, 196 Methine, dipteridyl-synthesis, 3, 303 Methine dyes, 1, 323-325, 332 L-Methionine, S-adenosyl-in metabolic iV-methylation, 1, 236 Methionine, dehydro- C NMR, 6, 139 X-ray crystallography, 6, 136 Methiothepin... 

In the turnip, the concentration was 63 p.p.m. Toxic action against various insects was established. Two cabbage varieties, cauliflower, brussels sprouts, broccoli, kale, mustard, and kohlrabi also contain 2-phenylethyl isothiocyanate as evidenced by gas liquid chromatography and bioassay. Only root tissues had insecticidal activity. 

Chrysanthemumic acid may exist in four stereoisomers, because of the two asymmetric carbon atoms in the cyclopropane ring. The natural acid has the D-trans configuration and this has been shown to be more insecticidally active than any of the other isomers or the racemic form. Harper et al, (4,18) have synthesized, separated, and optically resolved all of the isomers of this acid. 

Godin et al. (10), working on the effect of insecticidal activity of pyrethrum flowers from fresh and dried flowers, showed that extracts from fresh flowers had little or no greater effect on pyrethroid content and insecticidal activity than extracts from dried flowers with drying temperatures up to 80 °C. However, some of all the pyrethrin was lost at 120°C. The principal loss was in pyrethin I and not pyrethin II. 

Chrysanthemum dicarboxylic acid or pyrethric acid may exist in eight stereoisomers, owing to the trans or cis configuration on the side chain of the double bond as well as that of the cyclopropane. The natural acid has been shown to be the trans-trans acid. As in the case of the chrysanthemum monocarboxylic acid, the naturally occurring configuration is more insecticidally active than the racemic form or any of the three isomers synthesized. 

Sawicki and Elliott (31) re-examined the insecticidal activity of pyrethrin extracts and its four insecticidal constituents against four strains of houseflies, and checked the relative toxicity of pyrethrins I and II. This work confirmed the earlier results, showing that pyrethrin II was 1.3 to 1.6 times more toxic than pyrethrin I, but that the relative toxicities of pyrethrins I and II against the four strains of flies differed little. Resistance to knockdown but not to killing was associated in these strains with resistance to organophos-phorus and chlorinated insecticides. 

Bates, Hewlett, and Lloyd (2) therefore studied the synergistic effects of some compounds related to 2-diethylaminoethyl 2,2-diphenyl-w-pentanoate on the insecticidal activity of pyrethrins. They found active compounds when a 2-diethylamino moiety was joined to the diphenylmethyl moiety through an ester, ketone, or ether linkage. However, none of the compounds investigated approached piperonyl butoxide in synergistic activity with pyrethrins. 

There are several isomers of 1,2,3,4,5,6-hexachlorocyclohexane (HCH). The Y isomer is insecticidally active, whereas most of the others are relatively inactive. These compounds have been shown to activate inflammatory functions of neutrophils (35,36). Using Indo-1, we have characterized intracellular Ca mobilization in response to these compounds. Figure 9 shows the responses of cells labeled with Indo-1 to stimulation by y, < " P , and 6-HCH at a concentration of 260 pH. 

The increase in Ca is initiated rapidly and begins to recover after 1 min. The order of potency correlates fairly well with the solubilities of these compounds in organic solvents (37) and their abilities to accumulate in phospholipid vesicles (38), i.e., 6>y>a>p, but not with their insecticidal activity (y 6>a p 39). At these concentrations, crystals of p-, a-, and y-HCH were evident in the cell suspensions when we made simultaneous measurements of the right-angle light scatter, indicating that the order of aqueous solubilities is 6>y>a>p. However, stimulation by 6-HCH at concentrations below its aqueous solubility limit shows a typical dose dependency of the response (Figure 10). 

The first commercially available HCH insecticide sometimes misleadingly called benzene hexachloride (BHC) was a mixture of isomers, principally alpha HCH (65-70%), beta HCH (7-10%), and gamma HCH (14-15%). Most of the insecticidal activity was due to the gamma isomer (Figure 5.1), a purified preparation of which (>99% pure) was marketed as lindane. In Western countries, technical HCH was quickly replaced by lindane, but in some other countries (e.g., China) the technical product, which is cheaper and easier to produce, has continued to be used. HCH has been used as a seed dressing, a crop spray, and a dip to control ectoparasites of farm animals. It has also been used to treat timber against wood-boring insects. 

Rotenone A complex flavonoid produced by the plant Denis ellyptica. It has insecticidal activity due to its ability to inhibit electron transport in the mitochondrion. 

ISHIMOTO M, YAMADA T, KAGA A (1999) Insecticidal activity of an alpha-amylase inhibitor-like protein resembling a putative precursor of alpha-amylase inhibitor in the common bean, Phaseolus vulgaris L. Biochim Biophys Acta. 1432 104-12. 

Oxime carbamates are generally applied either directly to the tilled soil or sprayed on crops. One of the advantages of oxime carbamates is their short persistence on plants. They are readily degraded into their metabolites shortly after application. However, some of these metabolites have insecticidal properties even more potent than those of the parent compound. For example, the oxidative product of aldicarb is aldicarb sulfoxide, which is observed to be 10-20 times more active as a cholinesterase inhibitor than aldicarb. Other oxime carbamates (e.g., methomyl) have degradates which show no insecticidal activity, have low to negligible ecotoxicity and mammalian toxicity relative to the parent, and are normally nondetectable in crops. Therefore, the residue definition may include the parent oxime carbamate (e.g., methomyl) or parent and metabolites (e.g., aldicarb and its sulfoxide and sulfone metabolites). The tolerance or maximum residue limit (MRL) of pesticides on any food commodity is based on the highest residue concentration detected on mature crops at harvest or the LOQ of the method submitted for enforcement purposes if no detectable residues are found. For example, the tolerances of methomyl in US food commodities range from 0.1 to 6 mg kg for food items and up to 40 mg kg for feed items. ... 

Fraga, B. M. Diaz, C. E. Guadano, A. Gonzalez-Coloma, A. Diterpenes from Salvia broussonetii transformed roots and their insecticidal activity. J. Agric. Food Chem. 2005, 53, 5200-5214. 

Avilla, J. Teixido, A. Velasquez, C. Alvarenga, N. Ferro, E. Canela, R. Insecticidal activity of Maytenus species (Celastraceae) nortriterpene quinone methide against codling moth, Cydia pomonella (L.) (Lepidoptera Tortricidae). J. Agric. Food Chem. 2000, 48, 88-92. 

In continuing efforts toward the development of other nontoxic insecticides, many new products are being synthesized and tested. The direction of the synthetic work is guided by the theory that the insecticidal activity of a given substance is due to the combined influence of a toxic nucleus and modifying auxiliary groups. To illustrate the theory, this paper presents information on six materials related to piperonyl butoxide, when tested in combination with pyrethrins. 

Of five or more isomers, the only one that is appreciably insecticidally active is the gamma isomer, which occurs in various percentages, usually 12 to 13%, depending on methods of manufacture. This mixture of isomers results in a compound of strong and persistent odor, mostly due to the beta isomer, which odor is retained by some fruits, vegetables, and animal tissues after treatment for insect infestations. 

The chemistry, insecticidal, activity and toxicity of the major organofluorine insecticides are reviewed. In the ten years since the discovery of DDT opened up a new field of endeavor for the chemist, biologist, and toxicologist, activity in the field of fluorine-containing insecticides has been great. 

The discovery of the phenomenal insecticidal activity of 1,1, l-trichloro-2,2-bis(p-chlorophenyl)-ethane (DDT), which occurred less than 10 years ago, opened up a new field of endeavor for the chemist, biologist, and toxicologist. The activity in this field is considerable, and a portion of it has been directed toward efforts-to locate useful insecticides among the fluorine-containing compounds. Some of the fluorine compounds known to be insecticidal were re-evaluated, other compounds were tested biologically for the first time, and new compounds were prepared to be subjected to such tests. 

For the purpose of this review, the compounds considered are distributed among the following sections 1,1,l-trichloro-2,2-bis(p-fluorophenyl)-ethane, analogs of 1,1,1-trichloro-2,2-bis(p-fluorophenyl)-ethane, and miscellaneous organofluorine compounds. The chemistry, insecticidal activity, and toxicity of these groups of compounds are considered in the order given. Much of the work in synthetic insecticides, especially the biological portion, is necessarily of an exploratory character, and hence will have to be supported before appraisals become final. 

It is generally agreed that the contact-insecticidal activity of the DDT type of compound depends on at least one toxic component and the CC13 group or some other lipoid-soluble group for penetration. Beyond this point, there is a lack of agreement as to the exact mechanism by which the contact insecticides exert their action. 

Table III. Comparative Insecticidal Activity of DDT and DFDT against Insects of Diptera...

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