Acaricidal activity

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... 

In the early 1970 s potent acaricidal activity in 3-aryl-4-hy-droxy-coumarins. III, and 2-aryl-l,3-indanediones, IV, and their enol esters was discovered at Union Carbide (1,2). Extensive synthesis and screening of analogs in the dione and enol ester series led to the field test candidates Va and Vb, active against both motile forms (mite) and eggs. Va and Vb embodied certain structural and physicochemical features shown by published QSAR studies (2,3) to be important in determining the level of activity in the 1,3-indanedione series (1) the dimension D2 across the aryl ring must be near 7A and symmetry is preferred (2) the... 

Dithazolium salt (141) displays fungicidal and acaricidal activities <82JAP82l83770), and salts of the type (248) are shown to be inhibitors of biocorrosion of metals <90URP1587049). 

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. 

Table 1. Acaricidal activity of essential oil, linalool and artificial mixture from Lavandula angustifolia on Psoroptes cuniculi.

Ajoene, Fig. (10), an unsaturated sulfoxide disulfide, is the principal chemical responsible for garlic s anticoagulant properties. It has been also investigated for its acaricidal activity on T. urticae [275]. Complete mortality (100%) by ajoene was observed at 0.075% after 14 h of treatment, a dose comparable with other synthetic acaricides used in the experiment. At lower concentrations (0.05%), it affected female fecundity... 

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. 

Lee, C.-H., Sung, B.-K. and Lee, H.-S. (2006) Acaricidal activity of fennel seed oils and their main components against Tyrophagus putrescentiae, a stored-food mite. Journal of Stored Products Research 42(1), 8-1 4. 

As the table shows, phytotoxlclty of the spray dried formulation is much lower than the conventional formulation, viiille acaricidal activity is not significantly reduced. 

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. 

Amidoflumet is the only member in this class. It is an acaricide active against house dust mites. 

---