Synergism pyrethroids

Pyrethroid resistance in some strains of H. armigera is largely due to overproduction of specific esterase isoenzymes (Rni 0.24 0.33) which are thought to sequester and hydrolyse pyrethroids. The resistance factor is positively correlated to esterase litre, so that increasing resistance is accompanied by increasing esterase activity (Gunning et at.. 1996). Unfortunately, conventional esterase inhibitors, such as profenofos, have failed to synergize pyrethroids... 

The Use of Synergized Pyrethroids to Control Insect Pests in and Around Domestic, Industrial and Foodhandling Premises... 

Expected levels of synergized pyrethroids from these methods of treatment would be 4-12 mg m. Since only about one-third of this will reach the hori-... 

Grain protection by liquid and powder applications of synergized pyrethroids is discussed in detail elsewhere in this volume (see Chapter 16 by Mervyn Adams). The protection oi dried fruit from infestation by pyrethrins + PBO... 

Other cases of potentiation will be discussed in later chapters dealing with individual pollutants. These will include the synergism of pyrethroid toxicity to... 

Pilling, E.D. (1993). Synergism between EBI Fungicides and a Pyrethroid Insecticide in the Honeybee. Ph.D. Thesis Southampton University, U.K. 

Pilling, E.D., Bromley-ChaUenor, K.A.C., and Walker, C.H. et al. (1995). Mechanism of synergism between the pyrethroid insecticide lambda cyhalothrin and the imidazole fungicide prochloraz in the honeybee. Pesticide Biochemistry and Physiology 51, 1-11. 

Pilling ED, Jepson PC (1993) Synergism between EBI fungicides and a pyrethroid insecticide in the honeybee (Apis mellifera L.). Pestic Sci 39 293-297... 

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 ... 

Plapp, F.W., Jr., Synergism of pyrethroid insecticides by formamidines against Heliothis pests of cotton, /. Econ. Entomol., 72, 667,1979. 

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,... 

Figure 11,5, Relationship of maxi mum real factors of synergism of a range of pyrethroids to their activity alone at LD -, lewis.

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. 

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