Portal de Periódicos da CAPES

Mode of Action of Insecticide Synergists

1967; Annual Reviews; Volume: 12; Issue: 1 Linguagem: Inglês

10.1146/annurev.en.12.010167.001305

1545-4487

Robert L. Metcalf,

Insect Resistance and Genetics

Synergism, or the substantially more than additive toxic or pharmaco­ logical action of two substances used together, is a particular type of joint action which is the direct opposite of antagonism, in which the activity of a mixture is less than that of the more active constituent. As related to insec­ ticide action, synergism has generally been regarded as applying only where one component of a mixture, the synergist, is inactive at the dosage employed and where the mixture is appreciably more active than the other component alone. This convention, which will be followed generally in this review, sim­ plifies the demonstration of synergism, since the expected sum of the effects of two toxic materials used together is not always easy to determine. Ex­ cellent and comprehensive reviews of the mathematical basis for synergism have been produced by Hewlett (45) and by Sakai (99), and of insect toxicol­ ogy by Casida (19) and O'Brien (84) . Synergists are of practical importance to the entomologist (a) in the more economical or efficient control of insects by a mixture, e.g., the use of piper­ onyl butoxide, sulfoxide, n-propyl isome or sesamex with the expensive pyre­ throids ; (b) in increasing the spectrum of activity of an insecticide, e.g . , the use of carbaryl with piperonyl butoxide or other synergist to control the body louse or house fly; and (c) in restoring the activity of an insecticide against resistant strains of insects, e .g., the use of 1,1-bis-(p-chlorophenyl)-ethanol (DMC) or p-chlorobenzene N,N-dibutyl sulfonamide (WARF) as synergists for DDT against resistant house flies. As our knowledge accumulates, the use of synergist with insecticide may well provide the most feasible way to pre­ vent the development of resistant races of pests (45) . Quite apart from these important practical considerations, the funda­ mental investigation of synergism and synergists has led to a much better appreciation of the mechanisms of detoxication in insects, of the basic bio­ chemical processes involved in insecticide resistance, and of the mode of action of insecticides. Throughout this review the term, synergistic ratio, or SR will be used for LD60 of insecticide alone/LD5o of insecticide when applied together with the synergist. This ratio provides a fairly precise measure of the ease of detoxica­ tion of the insecticide and has been used widely by recent investigators under such terms as degree of synergism (35), synergistic activity (59, 106), co­ toxicity coefficient (20, 105) , and synergistic effect (45) .