Insecticides acaricidal activity

This class of pesticides comprises derivatives of tetronic acid. Spiromesifen belongs to this class. It is an insecticide/acaricide active against whiteflies and mites on vegetables, cotton, fruits, and ornamentals. Its oral LD50 in rats is >2500 mg/kg. 

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. 

Another incentive to this screening may have arisen from the discovery of two remarkably potent families of fermentation products with insecticidal and acaricidal activity, the milbemycins and the avermectins. Abamectin (a mixture of not less than 80% avermectin and not more than 20% avermectin is already... 

These derivatives were described as having strong insecticidal, acaricidal, and netnatocidal activity, along with low mammalian toxicity. 

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. 

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. 

The control of lice, mites and warbleflies continues to be achieved by the older agents. The selection pressure that caused resistance in cattle ticks and sheep blowfly has not been encountered by these other ectoparasites since their less frequent incidence has required less insecticide/acaricide usage. In addition to the OPs, rotenone (92) (the active principle of derris), an uncoupler of oxidative phosphorylation, continues to be used to combat mange. 

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 metabolism can completely mineralize the compound, although this process is usually relatively slow so that it is an effective insecticide, acaricide and nematocide. Anaerobically these compounds are hydrolyzed, and then mineralized by methanogens (61). 

Chlorfenapyr (Phantom ), a trifluoromethyl-containing pyrrole ring insecticide, belongs to a new class of uncouplers of oxidative phosphorylation [80], The original insecticidal lead that resulted in chlorfenapyr was the fermentation product dioxapyrrolomycin, isolated from a Streptomyces strain [81], The presence of the trifluoromethyl group is essential for a broad spectrum of insecticide and acaricide activity. 

Thiophosphoric and thiophosphonic acid ester aza analogues (297) of the benzoxazolone insecticide Phosalone (296) have high insecticidal, acaricidal and anthelmintic activities with very low mammalian toxicities (76HCA1593). 

Dihydro-2//-thieno[3,4-c]pyrazoI-3-yIcarbamates show insecticidal, acaricidal and nematocidal activity. 

Tetrachlorvinphos is an insecticide/acaricide with contact and stomach poison activity tor control of houseflies, poultry lice, mites (animal), ticks, etc. It is also used as larvicide for animal feed. Its oral LD50 in rats is >2000 mg/kg. 

Abamectin is an insecticide/acaricide that contains a mixture of avermectin Bja (>80%) and avermectin Bjb (<20%) as active ingredients. Avermectins, which are macrocyclic lactones, are derived from the actinomycete, Streptomyces avermitilis (soil microorganism). It is used to control insect and mite pests of a wide range of agronomic, fruit, vegetable, and ornamental crops. It is also used by home owners for control of fire ants. It has an oral LD50 in rats of 300 mg/kg. 

The compounds were evaluated for insecticidal and acaricidal activity against the following species cabbage looper (Trichoplusia ni [Hubner]), Mexican bean beetle (Epilachna varivestis Muls), southern armyworm (Spodootera eridania [Cram]), pea aphid (Acvrthosiphon pisum [Harris]), twospotted spider mite (Tetranvchus urticae [Koch]) and southern corn rootworm (Diabrotica undecimpunctata Howardi). 

The compounds were screened for insecticidal or acaricidal activity against five species Mexican bean beetle larvae... 

Some older compounds such as toxaphene, lindane and cyclodiene insecticides have been around for some time without their mode of action being known. My third observation is that, almost as a tradition, some insecticidal activity has been found and then later a physiological lesion has been discovered. The initial acaricidal activity of chlordimeform, the nematicidal activity of avermectin, or the diptericidal activity of cyromazine are good examples. 

Table I. Insecticidal and acaricidal activity of Delphinium extracts compared with MLA...

Nikkomycins are nucleoside amide antibiotics produced by Streptomyces tendae Tii 901 and are known to show antifungal, anti-insecticidal, and acaricidal activities. They are competitive inhibitors of chitin synthase. Nikkomycins are produced as a complex mixture, with nikkomycin Z (13) and nikkomycin X (14) representing the major components. ... 

Structually much more complex molecules have also been submitted to re-gioselective enzymatic hydroxylation. Two such examples have been described involving milbemycin, a sixteen-membered macrolide which exhibits broad-spectrum insecticidal and acaricidal activity, and monensin, a carboxylic polyether antibiotic193- 94l Milbemycin (Fig. 16.1-19) was thus regioselectively hydroxylated at the 13(3 position (followed eventually by a C-29 hydroxylation) to afford the 13P,29-... 

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