Acaricides milbemectin

Milbemectin, a synthetic avermectin-type product, is an insecticide/acaricide. It contains a mixture of milbemectin A3 and milbemectin A4. It is used for control of citrus red mites, pink citrus rust mites, and Kanzawa spider mites on citrus, tea, and others. Its oral LD50 in rats is 762 mg/kg. 

Milbemectin is a GABA agonist. Therefore, for those acaricides that also possess high insecticidal activity, they share the same modes of action as found in insects. Table 7.2 summarizes the biochemical sites of action of insecticides and acaricides. 

In 1990, milbemectin [a mixture of milbemycin A3 (tti) and A4 (0C3)] was launched as an acaricide on tea and eggplant. In the animal health field, milbemycin D was developed for the control of fatal canine heartworm disease, caused by Diwfilaria immitis, and launched in Japan in 1986. A mixture of the oxime derivatives of milbemycin A3 and A4 (milbemycin oxime) is used as a canine parasiticide. 

Milbemectin is isolated from the fermentation of Streptomyces hygrocopicus, another naturally occurring soil Actinomycete. It was introduced as an acaricide by Sankyo Co., Ltd. in 1990 (Table 29.6.2). 

Milbemectin is the name for a mixture of milbemycins A3 and A4, also referred to as milbemycin A3/A4. It was launched as an acaricide under the trade name Milbeknock by Sankyo in 1990. So far, it is the only milbemycin on the market for crop protection use. However, a second compound is expected to be launched by Sankyo, which became known as lepimectin (provisionally approved ISO common name) in 2004. Lepimectin is a semisynthetic derivative of milbemectin, thus containing an A3 and an A4 component, the latter being the major one. 

Table 29.6.4 shows the acaricidal and insecticidal activity of milbemectin, as described by Aold et al. [50]. Except for effects against some insects (Thrips and some Lepidoptera), milbemectin is mainly an acaricide. This is consistent with the structure-activity relationships observed with avermectin derivatives [28]. In general, compounds with Upophilic substituents on Cl 3 (or unsubstituted ones) are highly active, while polar substituents diminish the activity (cf Schemes 29.6.3 and 29.6.4). 

Milbemectin is mainly used as an acaricide against many important mites in tea and pome fruits, and also against pine wood nematode in Japan (Table... 

Neurotoxic compounds have been traditionally the largest category of acaricides, with several representatives from the organophosphate, carbamate, and pyreth-roid classes. Several new pyrethroid compounds such as acrinathrin, lubrocythri-nate and halfenprox and an analog of the macrolide abamectin milbemectin were recently introduced as acaricides. A completely new acaricidal chemistry has been found with carbazate chemistry [1]. 

---

See also in sourсe #XX -- [ ]

---