Acaricidal compounds

In 1976 scientists at the Merck Corporation discovered a complex of eight closely related natural products, subsequently named avermectins A through in a culture of Streptomjces avermitilis MA-4680 (NRRL8165) originating from a soil sample collected at Kawana, Ito City, Shizuoka Prefecture, Japan and isolated by the Kitasato Institute. Their stmctures are shown in Figure 1 (1 6). They are among the most potent anthelmintic, insecticidal, and acaricidal compounds known. 

Summarizing, the use of natural products as miticides in apiculture, with the exception of some substances, is not widespread. In extensive laboratory tests many compounds showed significant acaricidal properties. However, very few of them have proven to be effective when applied in field trials. Considerable variations in local environmental and colony conditions can affect efficacy. In case of mixtures, such as essential oils, the difficulty in obtaining standardized compounds also affects treatment predictability. Nevertheless, identifying new acaricide compounds with low toxicity to honey bees is fundamental for providing candidate compounds for field trials. Furthermore, the development of... 

It appears that spider mite resistance, or, more precisely, spider mites which possess heritable, substantial reductions in susceptibility, occur to essentially all of the acaricides widely used in agriculture, and possibly for some newer classes of acaricidal compounds that have not been widely employed to-date. Therefore, for most acaricides it is not a question of whether resistance exists per se, rather it is of greatest relevance to determine if problematic frequencies of resistant mites occur at specific locations and, through research, determine what management efforts will keep frequencies of resistant pests below those which impair field performance of acaricides. 

Oxadiazine derivatives are widely used in agrochemistry as insecticides, herbicides, fungicides, and pesticides. For example, 2-aryl-4-alkyl-5,6-dihydro-l,3,4-oxadiazines are useful insecticidal and acaricidal compounds... 

The avermectins are a group of closely related 16-membered macrocyclic lactones extracted from a fermentation broth produced by a culture of Strepto-myces avermitilis MA-4680 (NRRL 8165) isolated at the Kitasato Institute from a soil sample collected at Kawana, Ino City, Shizuoka Prefecture, Japan [4]. They are the most potent anthelmintic and acaricidal compounds known. Avermectin structures are shown in Fig. 1. 

The scabies mite, Sarcoptes scabiei van hominis, is becoming increasingly resistant to existing acaricidal compounds such as lindane, benzyl benzoate, permethrin, and oral ivermectin. The potential use of a 5% M. alternifolia essential oil solution to treat scabies infections was investigated in vitro. It was found to be highly effective at reducing mite survival times, and the main active component was terpinen-4-ol. However, the in vivo effectiveness was only tested on one individual, in combination with benzyl benzoate and ivermectin (Walton et al., 2004). 

Karathane A trade name for 2,4-dinitro-6-( 1 -methylheptyl)phenyl crotonate, CJ8H24N2O6, a compound which has both acaricidal and fungicidal activity. It is a red-brown oil of high boiling point, insoluble in water but soluble in most organic solvents. Karathane is used for the control of powdery mildew, and is nontoxic to mammals. 

Carbamates such as Aldicarb undergo degradation under both aerobic and anaerobic conditions. Indeed the oxidation of the sulfur moiety to the sulfoxide and sulfone is part of the activation of the compound to its most potent form. Subsequent aerobic metaboHsm can completely mineralize the compound, although this process is usually relatively slow so that it is an effective iasecticide, acaricide and nematocide. Anaerobically these compounds are hydrolyzed, and then mineralized by methanogens (61). 

Dicofol [54532-36-4] l,l-bis(/)-chlorophenyl)-2,2,2-trichloroethanol, R = Cl (139), is a white crystalline soHd (mp 79°C). This compound is insoluble in water and soluble in organic solvents, and in the presence of alkaU forms the inactive/),/) -dichloroben2ophenone and chloroform. Dicofol is a long-lasting acaricide and is active against all stages of mites. The rat oral LD qS are 809, 684 mg/kg. 

The compounds represented by general formula 117 are useful as a insecticides, acaricides, and bactericides (99INP9946247). 

Most analytical work on sulphones has naturally been concerned with the compounds synthesized for special purposes, e.g. sulphonal, trional and tetronal as sedatives and hypnotics Sulphenone (4-chlorodiphenyl sulphone) and Tedion (2,4,4, 5 -tetrachlorodiphenyl sulphone) as acaricides 4,4 -diaminodiphenyl sulphone as an antileprotic. In choosing examples preference has been given to methods devoted to more than a single sulphone. 

The rapid rise in the industrial (catalyst in PVC and foam production), agricultural (fungicides and acaricides), and biological applications (wood, stone, and glass preservatives) of organotin(IV) compounds during the last few decades has led to their accumulation in the environment and, consequently, in biological systems. 

The next major discovery in this field, which was the result of a joint research effort in 1968 between M and T Chemicals, Inc., and the Dow Chemical Company in the United States (475, 524), was that tricyclo-hexyltin hydroxide ("Plictran ) possesses a very high activity against certain types of mites, and this compound was subsequently introduced by Dow as an acaricide for use on apple, pear, and citrus-fruit trees. A second triorganotin acaricide, bis(trineophyltin) oxide ("Vendex or "Torque ), has recently been introduced by Shell Chemical Company (476). Two other tricyclohexyltin compounds are currently under de-... 

This is a large subject that can only be dealt with in the barest outline in the present text. Many antibacterial and antifungal compounds have been discovered in microorganisms, and some of them have been successfully developed as antibiotics for use in human and veterinary medicine. They lie outside the scope of this book. A considerable number of other microbial compounds act as insecticides, acaricides, or herbicides, although few of them have been developed commercially (Copping and Menu 2000, Copping and Duke 2007). 

Paraquat Pesticides (includes acaricides, avicides, bactericides, insecticides, molluskicides, nematocides, piscicides, rodenticides) L S Chlorinated hydrocarbons (q.v.) Carbamates (q.v.) Organophosphorus compounds (q.v.) Herbicide... 

The avermectins, a family of compounds with potent anthelmintic, insecticidal and acaricidal activity, have vividly demonstrated that fermentation products can have entirely unanticipated activities. Besides their utility in animals, they show great promise for the control of insect pests of plants. Although antibiotics have found only a limited role in the control of plant diseases, the desire to find environmentally acceptable alternatives to the chemicals currently used has prompted new research efforts to discover fermentation products for use as pesticides. 

Results from these laboratory studies demonstrated that avermectin Bj had high toxicity for the twospotted spider mite (Tetranychus urticae) on bean plants. When applied in solution directly onto adult and nymphal spider mite populations on foliage, avermectin Bj was shown to be 50-200 times as potent as commercially available acaricides, with an LC q of 0.02-0.03 ppm. Additional tests on foliage with insects in the order Lepidoptera, Coleoptera, Homoptera, Orthoptera, Diptera, Isoptera and Hymenoptera confirmed the broad spectrum activity and potency of the avermectin family of compounds and avermectin Bj in particular. Table II provides LC q values for avermectin Bj for the control of larval forms of several of these insects in foliar residue assays (18). 

Thiazetidines are investigated with special emphasis on their possible antiradiation drug activity. Certain 1,3-thiazetidines exhibit pesticidal activity. Compounds 21 are specifically eflective as insecticidal and acaricidal agents. 

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. 

Alkyl(aryl)-2-(trifluoromethyl)-5(277)-oxazolones have been used as intermediates to prepare 2-(trifluoromethyl)pyrroles interesting compounds frequently used as insecticides and acaricides. The oxazolones react with electron-dehcient unsaturated compounds in the presence of a base. Reaction of 5(277)-oxazolones, usually with a substituted aryl ring at C-4, with a wide variety of alkynes and alkenes has given rise to numerous 2-(trifluoromethyl)pyrroles 56. For example,... 

A recently introduced insecticide/acaricide, chlorfenapyr (Figure 3.14), has been shown to disrupt the electrochemical gradient in mitochondria and, thereby, uncouple oxidative phosphorylation. There is also evidence that the compound is a pro-insecticide, being converted into the active form by mixed function oxidases within the insect or mite. 

Tin-containing compounds have been used in agriculture for many years as both fungicides (Chapter 4) and as acaricides. Tricyclohexyltin hydroxide and several related compounds (Figure 3.20), are very active against adult spider mites and are believed to act through an inhibition of oxidative phosphorylation. 

A pioneering study by Baker and Krantz (1984) demonstrated the use of an alarm pheromone for R. robini (identified at the time as neral (2) plus geranial (6)) in combination with acaricides for mite control. The results appeared promising in principle, but in practice, use of mite alarm pheromones for control of pests infesting stored products may not be feasible because of the strong and often offensive odors and flavors of the compounds. 

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