Pyrethroid spray

However, the attributes that made them attractive also created concern about the evolution of resistance to these compounds. Their effectiveness has resulted in overuse in many areas of the world. In Thailand for example, farmers have been known to apply as many as 20 pyrethroid sprays per season (H.) In... 

Since pyrethrins are highly photolytic, antioxidants are often added to preparations to stabilize formulations antioxidants adjoin include pyrocatechol, pyrogal-lol, hydroquinone, and l-benzene-azo-2-naphthol. Practically, all pyrethrins and many pyrethroids are commonly combined to additives (including synergists), some formulations include additional insecticides, insect repellents, or both, and many contain hydrocarbon solvents [3] to enhance their insecticidal activity. Pyrethrin and pyrethroid sprays may also be water based or be alcohol or petroleum based, which increases the overall toxicity. It is known that concomitant use of pyrethrins and pyrethroids with synergists such as piperonyl butoxide, A -octyl bicycloheptene dicarboximide, sulfoxide, sesamin, sesame oil, sesamolin, isosafrole, and organophosphorus compounds or carbamates may increase toxicity by mechanisms involving inhibition of microsomal oxidation [4]. 

A pyrethroid spray may be required in October/November if scarring by the larvae is found on more than 70% of leaf petioles. (Scarring may be seen as brown or brownish-purplish pitting on the upper surface of the leaf petiole.)... 

S Hewitt, M Rowland, N Muhammad, M Kamal, and E Kemp. Pyrethroid-sprayed tents for malaria control An entomological evaluation in Pakistan. Med. Vet. Entomol. 9 344—352, 1995. 

Anthrahydroquinones have been patented in Japan as bird repeUents (73), and anthraquinone [84-65-1] (qv) is used widely in Europe as a spray to protect growing crops and as a wood dressing. The synthetic pyrethroid deltamethrin [52918-63-5] (27) was evaluated (74), as were other materials, including bendiocarb (20) (75) and 20,25-dia2ocholesterol dihydrochloride [1249-84-9] (Omitrol) (28), a steroid that inhibits embryo development when adsorbed or ingested as a seed treatment of bait com (55,76). 

Pyrethrum became the main source of household insecticides in sprays in the USA (1919) and mosquito coils (1895) as well as oil-based preparations (1924) in Japan. Thereafter, the insecticidal ingredients shifted from pyrethrins to various synthetic pyrethroids, but mosquito coils have been used worldwide for more than 110 years without changing in shape. 

A recently commercialized U.L.V. (ultra-low volume) -type aerosol sprays a fixed volume of ultra-fine particles into the room and retains effectiveness for 12 h with one spray. The mechanism of the effectiveness was considered to be the contact of pyrethroid particles with mosquitoes in the air at the initial stage followed by re-volatilization into the air of pyrethroids attached to walls and floors however, according to experiments by the present author et al., it was confirmed that mosquitoes are knocked down by contact with pyrethroid particles in the air during the first 1 h and then the lethal effect on mosquitoes is achieved by their contact with pyrethroids adhering to walls. 

Gersdorff WA, Piquett PG (1961) The relative effectiveness of two synthetic pyrethroids more toxic to houseflies than pyrethrins in kerosene sprays. J Econ Entomol 54 1250-1252... 

Only countries with political clout and political sense about DDT, notably South Africa, China, and India, still use it. South Africa had stopped using DDT in 1996 under pressure to join the world s Green community and switched to the next best alternative, the synthetic pyrethroids, which are three times the price and are effective over a shorter time span. Four years later, in 2000, South Africa decided to resume DDT spraying after malaria cases jumped by 1,000 percent because of mosquito resistance to the synthetic pyrethroids. 

The persistent pyrethroids such as permethrin, cypermethrin, cyfluthrin, and fenvalerate are effective mothproofing agents when applied as spot treatments from ready to use (RTU) formulations. Sodium fluosilicate [16893-85-9] is an effective mothproofing agent used at 0.5 to 0.7% in water solution with 0.3% potassium aluminate and 0.03% oxalic acid, and applied to fabrics by spraying or dipping. It is not removed by dry cleaning. 

Pyrethroids are synthetic esters produced to imitate or improve the activity of biological principles of the pyrethrum plant. They are powerful contact insecticides causing rapid knockdown of treated insects. The pyrethroids are extensively used in controlling insect pests on fruit trees, vegetables, and other field crops in space sprays and contact sprays to kill insects infesting homes, industrial locations, and nonfood processing areas and in protection of warehoused food. These compounds include fenvelerate [51630-58-1], (7), R = Cl flucythrinate [70124-77-5], (1) R = CHF20 allethrin [584-79-2] (8) cyfluthrin [68359-37-5] (9) cypermethrin [52315-07-8] (10) deltamethrin [52918-63-5] (11) permethrin [52645-53-1] (12) and tetramethrin [7696-12-0] (13). 

In the indoor environment, many types of products such as crystals, sprays and liquids are applied for active and preventative protection of insects. Insect sprays are particularly popular because they are easy to handle and can be combined with air fresheners. Commonly, the amount of active agents in these products is well below 2%. For example, a commercially available insecticide for indoor use may contain 0.25% tetramethrin, 0.05% D-phenothrin and 1% of the synergist pipero-nyl butoxide. Pyrethroids are also used as active agents in liquid products against furniture beetle. In addition, materials containing natural fibers are often equipped with synthetic pyrethroids as a precaution. Apart from the active ingredients, volatile components such as acetone, aliphatic hydrocarbons, cycloalkanes, branched alkanes C3-benzenes and dipropylene glycol monomethyl ether are usually present in insecticides. 

Malaria vector control accounts for 80-90% of total pesticide use for public health purposes. Residual spraying uses the greatest volume of insecticides. However, the treatment of mosquito nets and other materials with pyrethroid inseetieides is becoming an additional important method for personal protection and reduction of transmission of malaria. 

DDT continues to be the pesticide most used in malaria vector control programmes in the Region with no significant decrease in overall quantities, although in some countries use has declined considerably. The introduction of insecticide-treated mosquito nets and the replacement of DDT by synthetic pyrethroids for indoor residual spraying have contributed to an increase in the public health use of pyrethroids. 

Organophosphorus and pyrethroid insecticides are being used for indoor residual and space spraying for the control of malaria and other vectors and pests of public health importance. 

A wide range of insecticides from all major groups is used for public health purposes. For malaria control, only WP formulations are used for indoor residual spraying, while EC formulations are used as larvicides. UL and thermal fogging with malathion or pyrethroids have been used during malaria epidemics. For insecticide-treated mosquito... 

For dengue, space spraying is used for epidemic control. Malathion, previously the insecticide of choice for dengue control, is slowly being replaced by pyrethroids, including a water-based formulation (EW). Larvicides including temephos and Bti are also used for the control of the two main vectors, A. aegypti and A. albopictus. Limited temephos resistance has been reported but does not appear to be a major problem. 

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