Laboratory Evaluation of Certain Organophosphorus Insecticides Against the Red Palm Weevil, Rhynchophorus ferrugineus (Olivier)

(Ajlan, A. M.; M. S. Shawir; M. M. Abo-El-Saad, M. A. Rezk and K. S. Abdulslam)

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Abstract

Five organophosphorus insecticides; pirimiphos-methyl (Actellic), chlorpyrifos (Scidofos), fenitrothion (Senthion), trichlorphon (Cekufon) and oxydemeton-methyl (Amicosystox) were evaluated under laboratory conditions against larval and adult (male & female) stages of Rhynchophorus  ferrugineus (Olivier) collected from Eastern Province, Saudi Arabia. Values of LC50 and LC95 showed that, pirimiphos-methyl was more potent against males and females, whereas, chlorpyrifos was less in this respect. In the meantime, oxydemeton-methyl showed greatest insecticidal activity against the larvae. Relative toxicities, based on LC50 and LC95 values, showed that pirimiphos-methyl was 19.1, 19.0 and 1.3 times more toxic than chlorpyrifos, to the males, females and larvae, respectively. However, based on LC95 values, and after 24 hrs of exposure, pirimiphos-methyl was 1.7, 15.8 and 1.1 times more toxic than chlorpyrifos to the same life stages. Moreover, the data clearly indicated that either pirimiphos-methyl at 0.2% or oxydemeton-methyl at 0.36% is sufficient to kill larval and adult stages of the weevil within three days. A mixture of pirimiphos-methyl and either oxydemeton-methyl or trichlorphon is suitable to control the larval and adult stages of R.  ferrugineus.
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