Pestic. Sci. 1976, 7 , 223-224

Introduction

Chemistry, Biochemistry and Insecticidal Action of Natural and Synthetic Pyrethroids"

Michael Elliottb

Department of Insecticides and Fungicides, Rothamsted Experimental Station, Harpenden, Hertfordshire AL5 2JQ

(Manuscript received September 1975)

Other sessions of the Congress discussed the organophosphorus compounds, organochlorine compounds and carbamates. It was appropriate to consider also pyrethroids to assess what part they are playing in insect control and what may be expected of them in the future. At the present time it would be very desirable, for many reasons to be able to introduce new types of insecticide and to use insecticides of greater potency to insects and lower toxicity to mammals, so diminish- ing environmental contamination. The results shown in Figure 1 are relevant to this theme.

E Organophosphates 0 Carbomates Organochlorines Pyrethroids

Musca Phaedon Anopheles Glossma Sfatnoxys dornesfica cochleariee stephensi austeni calcifrans

0.0 I

0. I

I

10

Figure 1. LDm values of insecticides.

The LD50 values in mg/kg of representative members of four groups of insecticides are shown against five insect species. In this comparison, where tests were made by topical application of measured drops, many complications are necessarily bypassed, but the results indicate what potent insecticides pyrethroids are with activities down to the 0.01 mg/kg range. None of the data was obtained in the presence of synergists. With synergists, some of the non-pyrethroids would be

A session at the IUPAC Third International Congress of Pesticide Chemistry, Helsinki, 3-9 July 1974. Session organiser. The following are a selection of those presented at Helsinki.

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224 M. Elliott

10-20 times more active-but so would pyrethroids. The lowest LD.50 for the housefly with syner- gist pretreatment is 0.02 ng/insect, which is about 0.002 mg/kg.

This level of potency, albeit in laboratory tests and under specialised conditions, justifies the time given to the subject of pyrethroids at the Conference and the conclusion may be drawn that they can be expected to play an increasingly important role in insect control.