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Rearing Pseudotheraptus wayi Brown (Coreidae) a pest of coconuts in East Africa, and evaluation of its susceptibility to various insecticides.

Published online by Cambridge University Press:  10 July 2009

P. E. Wheatley
P. E. Wheatley
Affiliation:
Entomologist, Department of Agriculture, Kenya.
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Extract

A method is described for the large-scale rearing of Pseudotheraptus wayi Brown, the Coreid causing immature nutfall of coconuts in East Africa.

Adults were kept in cages with sides of thick white drill and wire-gauze, in an outdoor insectary at Matuga, near Mombasa, Kenya, and were provided with freshly collected fallen nutlets from which the bracts had been removed. Eggs were normally laid on the walls of the cage. The nutlets were replaced every two days, and all newly hatched nymphs removed and placed in other cages supplied with fresh nutlets every second day. There was some mortality in the first- and second-instar nymphs due to the handling entailed when nutlets were replaced, but in the later nymphal stages it was very low. Under these rearing conditions, the life-cycle from egg to adult was completed in from 35 to 40 days.

The toxicities to Pseudotheraptus of dieldrin, DDT, γ BHC, malathion and pyrethrins in a solvent were compared by topical application of measured-drop doses from an Agla micrometer syringe in a range of five concentrations (except for DDT, where eight concentrations were used). The mortality counts at 72 hr. were taken as the measure of toxicity.

Analysis of the log dosage/probit regression lines indicated that dieldrin was markedly more toxic than DDT to Pseudotheraptus, and that the toxicity to this insect of pyrethrins was of a very low order.

In a supplementary experiment to determine whether the addition of resin improved the toxicity of DDT when applied topically, batches of adults were treated with measured drops of a solution of p, p'DDT (0·5 per cent, for females, 0·25 per cent, for males) and others with the same concentrations of DDT to which coumarone indene resin at one-tenth of the DDT content had been added. The toxicity of the DDT was not enhanced.

Type
Research Paper
Information
Bulletin of Entomological Research , Volume 51 , Issue 4 , January 1961 , pp. 723 - 729
Copyright
Copyright © Cambridge University Press 1961

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