Pyrethroids synergists

These examples of the limitations of bioassay methodology show that comparative interpretations of data from various sources can be confused and so lead to ill-reasoned conclusions of both the extent and description of resistance and synergism. As Yamamoto (1973) wrote. Synergistic effect is greatly influenced by the lest insect, formulation, pyrethroid-synergist ratio, method of administration and choice of response, cither kill or knockdown these experimental differences complicate [the] interpretation of results/ However, it is only on the basis of sound toxicological evidence that any theories concerning the mode of action of PBO, either alone or when in combination with another compound, must be founded. 

Bioassay data for the H. armi era strains arc shown in Tabic 13.1. Strains were 1U-, 30- and 60-fold resistant to fen valerate. Profenofos was ineffective as a pyrethroid synergist, but PBO rendered the 10-fold-resistant strain almost completely susceptible to fen valerate, In the more highly resistant populations (30-and 60-fold), PBO was much less effective. 

Uses Insecticide pyrethroid synergist Manuf./Distrib. Supelco http //www.sigma-aldrich.com... 

Here R, R2, and R3 have a multiplicity of organic functions, and these materials synergize many insecticides. In piperonyl butoxide, an important pyrethroid synergist, the Ri group is butoxyethoxyethyl. In addition there also is a propyl group in the 6-position in piperonyl butoxide. Certain alkyne, hetero-... 

Gas ehromatography mass-mass aequisition was used for the pyrethroid determination. Pyrethroids investigated were Allethrin, Prallethrin, Tetramethrin, Bifenthrin, Phenothrin, X-Cyhalothrin, Permethrin, Cyfluthrin, Cypermethrin, Flueythrinate, Fsfenvalerate, Fluvalinate and Deltamethrin. Piperonyl butoxide, main synergist eompound for pyrethroid eompounds, was also studied. 

Bromley-Challenor, K.C.A. (1992). Synergistic Mechanisms of Synthetic Pyrethroids and Fungicides in Apis Mellifera. M.Sc. Thesis, University of Reading, UK. 

Mainly against the Group III mosquitoes, Katsuda et al. investigated the efficacy of mosquito coils containing various pyrethroids. In the 25-m3 semi-field test shown in Table 9, mosquito coils with d.d-Y-prallethrin at concentrations of 0.1-0.15% plus a synergist, /V-(2-ethylhexyl)bicyclo 2.2.1 -hept-5-ene-2,3-dicarboxyimide (39, Fig. 11), were effective even for the allethrin-resistant A. aegypti. 

Katsuda Y, Leemingsawat S, Thongrungkiat S, Komalamisara N, Kanzaki T, Watanabe T, Kahara T (2008) Control of mosquito vectors of tropical infectious diseases (1) bioefficacy of mosquito coils containing several pyrethroids and a synergist. Southeast Asian J Trop Med Public Health 39(l) 48-54... 

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. 

Examples of these include sesamin and sesamolin, both active principles of sesame oil, and piperonyl butoxide (PBO) and sesamex, both synthetic products. Although initially developed for use with pyrethrins, they have since been observed to synergize some, but not all, carbamates, organophosphates, pyrethroids, and organochlorines. In addition to the MDP compounds, another type of synergist called MGK 264 was developed to synergize the toxicity of pyrethroids and rotenone. The structure of piperonyl butoxide and MGK 264 are as follows ... 

Piperonyl butoxide is a synergist for carbamates, pyrethrins, pyrethroids, and rotenone. 

The pyrethrins and some pyrethroids are commonly co-formulated with the synergist, piperonyl butox-ide. This has limited toxic potential in itself but inhibits both oxidative and hydrolytic detoxification reactions and so enhances their toxicity - especially to insects. 

Pyrethrins and synthetic pyrethroids are among the safest of the topically applied ectoparasiticides, because of their selective toxicity for insects (mam-malian-to-insect toxic dose ratio is greater than 1000, compared with 33 for organophosphates and 16 for carbamate insecticides). In contrast to the very wide margin of safety for mammalian species, pyrethroids are toxic to fish. The synergistic action of pyrethrins and piperonyl butoxide (in combination preparations) is due to the inhibition by piperonyl butoxide of the microsomal enzyme system of some arthropods. Preparations of synthetic pyrethroids (permethrin, cypermethrin) often contain a mixture of drug isomers in varying proportions. 

PBO has not been used as an internal medicine in humans. This compound has, however been extensively used both as a synergist with pyrethrins or pyrethmids for the control of household pests and its. an agricultural insecticide. PBO has been incorporated in millions of aerosols utilized in homes, offices and factories, Furthermore. PBO has had very extensive dermal application to humans in combination with both pyre thrum and pyrethroids (e.g, permethrin) for the control of head and pubic lice, as well as scabies infestations. Such exposure has been on-going for over 40 years, with most applications being to children. The absence of untoward eHeels with the tthove uses serves to under line the wide safety margin of this compound. 

Bruce (1967) deveioped a method based on a gas chromatograph equipped with a specially constructed electron capture cell. This detector cell was claimed to allow the determination of extremely low quantities (picogram levels) of organophosphorous and pyrethroid insecticides, as well as synergists in food, feeds and water Moore (1972) analysed PBO residues in different foodstuffs (oils and fats, potato chips, bacon, chicken and eggs, dried codfish) by means of the Bruce gas chromatographic method. 

PRO (Fig. 9.1) is an economically important, widely used synergist of natural pyrethrins and synthetic pyrethroid insecticides with ait excellent record of human health anti safety over the 40 years or so since its introduction. Most pynelhnoids have a good record of environmental and human safety in the absence of PBO. a much greater tonnage of more potent, synthetic insecticides would be required to achieve the same levels of insect control, with potential adverse consequences for the natural environment. 

Although the individual pyrethroids in the study were tested independently, the data in Tables 11-8 and 11-9 demonstrate basic principles of synergistic action. Table 11.8 shows the pyrethroids in order of their maximum additive factor of synergism by ratio. The conventional factors of synergism at these nitios are larger. It will be noted that the levels of PBO at these maximum factors of synergism are basically in reverse order and range from approximately I to 13 pg per insect,... 

---