Vaporizers, metofluthrin

Metofluthrin is a newly developed highly effective pyrethroid which has excellent insecticidal activity against mosquitoes. Due to its superior characteristics, Metofluthrin is suitable for use in various types of mosquito control formulation, including mosquito coils and liquid vaporizers. Metofluthrin also has excellent... 

Ujihara K, Mori T, Iwasaki T, Sugano M, Shono Y, Matsuo N (2004) Metofluthrin a potent new synthetic pyrethroid with high vapor activity against mosquitoes. Biosci Biotechnol Biochem 68(1) 170-174... 

Table 2 Efficiency of metofluthrin in a non-heating vapor formulation with a fan and mosquito coil formulations aganinst various mosquito species ...

Abstract Metofluthrin (commercial name SumiOne, Eminence ) is a novel pyrethroid insecticide developed by Sumitomo Chemical Co., Ltd. Metofluthrin has extremely high insecticidal activity to various pest insects, especially to mosquitoes. In addition, Metofluthrin has relatively high volatility and low mammalian toxicity. Metofluthrin is therefore suitable for use not only in conventional mosquito control formulations such as coils and liquid vaporizers, but also in a variety of novel devices that do not require heating, such as fan vaporizers and paper and resin emanators. Here we describe the insecticidal activity of Metofluthrin mainly against mosquitoes in various formulations in both laboratory and field trials. 

Table 5 Knockdown efficacy of Metofluthrin liquid vaporizer (60 days use formulation) against Culex pipiens pallens (laboratory strain) large chamber (28 m3) cage method...

Table 7 Knockdown efficacy of Metofluthrin liquid vaporizer against Culex quinquefasciatus (Bogor field strain) by the large chamber free-flying method with 1 h pre-fumigation ...

One of the major characteristics of Metofluthrin is its vapor action at room temperature not seen in the existing pyrethroids D-allethrin and prallethrin. We will describe a fan type formulation ( a fan vaporizer ) where a motor turns a fan and the active ingredient is vaporized by the airflow from it at room temperature. 

Fig. 4 Knockdown efficacy of Metofluthrin(=160 mg) fan vaporizer against Culex pipiens pallens (susceptible strain) compared to commercial liquid vaporizer (prallethrin = 600 mg)...

Fig. 6 Field efficacy of Metofluthrin liquid vaporizers against indoor night biting mosquitoes, evaluated in homes in Indonesia and in Malaysia...

In the treated homes, one liquid vaporizer was switched on and placed on the floor in the living room, approximately 1-1.5 m away from the human bait. Results obtained from the two trial sites indicated that liquid vaporizers containing 0.11 wt % Metofluthrin were slightly inferior to those containing 0.86 wt% prallethrin. However, the percentage of bite reduction provided by 0.17 wt% Metofluthrin was similar to, or better than, that provided by 0.86 wt% prallethrin (Fig. 6). Therefore, the relative efficacy of Metofluthrin in liquid vaporizer formulations is at least five times better than prallethrin. 

Natural vaporization agents, where the active ingredient is formulated on paper or resin, and where it is vaporized without heating or use of power, are easy to use, so there is particular high potential for associated new developments in the field of mosquito control. Insecticides that can be used in formulations for this purpose must possess the characteristics of room temperature vapor action, high level activity, and a high degree of safety for mammals. Metofluthrin meets all of these requirements. 

We carried out a detailed investigation into the performance of metofluthrin in mosquito coils and liquid vaporizers, the most commonly used forms of heated mosquito control devices. 

Figure 9. Knockdown efficacy of metofluthrin vaporizer liquid against Culex quinquefasciatus (Bogor, field strain) by large chamber free-flying method, 1-hour pre-fumigation.

Table III. Knockdown efficacy of metofluthrin fan vaporizer against Culexpipiens (laboratory strain).

Pyrethroids with a high vapor pressure, such as metofluthrin, transfiuthrin, and allethrin, evaporate faster at ambient temperatures, resulting in high-vapor-phase concentrations of active ingredients that can produce a barrier effect. Evaporation rates are farther enhanced in product... 

Another active-emission technology uses a fan to disperse vapors from a material that volatilizes under ambient conditions. The U.S. EPA has registered several products that consist of a cartridge containing either linalool or geraniol inserted into a stationary fan device that disperses the repellent vapors. Recently, several wearable personal repellent devices have received EPA registration. These devices consist of a small battery-powered fan and a repellent matrix treated with an active ingredient (metofluthrin, a pyrethroid or a mixture of essential oils) that volatilizes at ambient temperatures. The devices create a cloud of mosquito-repellent vapor around the wearer. 

Thresholds exist for when and how insects respond to these chemical actions. These thresholds are governed by intrinsic factors related to the mode of action of the chemical and the insects susceptibility, as well as by extrinsic factors that modify those effects. Among the extrinsic factors, the physical environment, humidity, air movement, and temperature can affect the volatility of the active ingredient. The dose-dependent order in which thresholds are exceeded determines whether the primary mode of chemical action is repellent, irritant, or toxicant. Some pyrethroids can produce excitorepellency with possible mortality as a result of the exposure. Other pyrethroids with sufficiently high vapor phase concentration, for example, metofluthrin and transfluthrin, can result in a spatial repellent (barrier) effect regardless of knockdown and mortality of insects. 

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