FACTORS INFLUENCING THE EFFECTIVENESS OF CERTAIN NOVEL INSECTICIDES AGAINST RED PALM WEEVIL

The present work was carried out at the Middle East Regional Laboratory of red palm weevil, El-Kassasin, Ismalia Governorate to evaluate the efficiency of four synthetic insecticides (i.e., Chlorpyifos, Imidacloprid, Chlothianidine 50% WG and 16% SG) compared with two bio-insecticides (i.e., Beauveria bassiana and Bt. toxin) against full grown larvae and adults of red palm weevil, Rhynchophorus ferrugineus (Olivier) under laboratory conditions. The obtained results showed that the rate of toxicity varied tremendously according to the nature of the applied toxicant, used concentration, time elapsed after exposure and the treated stage. Also, as the time after application progressed there was an increase in the rate of accumulated mortality. The full grown larvae proved to be more susceptible when compared with the adult stage. Imidacloprid seemed to be the most effective toxicant against full grown larvae when compared with the other tested synthetic insecticides. In case of adult stage, Chlorpyrifos proved the most influential in this respect. Regarding the two tested biocides, the LC₅₀s of Beauveria bassiana after 15 days showed 1.08×10⁵ and 2.2×10⁵ spores/ml against full grown larvae and adult stage, respectively. In case of Bacillus thuringiensis it gave 798.73 and 7600 ppm, against full grown larvae and adult stage, respectively.