THE INSECTICIDAL ACTIVITY OF SOME SYNTHETIC ORGANO‐PHOSPHORUS COMPOUNDS

Abstract

The toxicity of a series of organo‐phosphorus compounds to the overwintering eggs of Aphis pomi Deg., Operophtera brumata (L.) and Metatetranychus ulmi (Koch) was examined by a laboratory technique. The eggs of M. ulmi were highly resistant to all the compounds tested, those of Operophtera brumata were most susceptible to P‐nitrophenyl diethyl thionphosphate (E 605) and those of Aphis pomi to p‐nitro‐phenyl diethyl phosphate (E 600). With analogues of the last‐mentioned compound there is evidence that their toxicity to A. pomi eggs is associated with the presence of electron‐attracting substituents in the benzene nucleus. A number of organo‐phosphorus compounds, including hexaethyl tetraphosphate and p‐nitrophenyl diethyl thionphosphate, were highly toxic under laboratory conditions to the active summer stages of Metatetranychus ulmi, but the summer eggs of this mite were rather more resistant. Field trials of hexaethyl tetraphosphate and p‐nitrophenyl diethyl thionphosphate for the control of the aphids Brachycaudus helichrysi (Kalt.), Phorodon hutnuli (Schr.) and Aphis pomi Deg. showed these substances to be effective substitutes for nicotine.