THE INFECTIVITY OF ENTOMOLPATHOGENIC FUNGI BEAUVARIA BASSIANA AND METARHIZIUM ANISOPLIAE TO RHYNCHOPHORUS FERRUGINEUS (OLIVIER) STAGES UNDER LABORATORY CONDITIONS

Two entomopathoginic fungi, Beauvaria bassiana and Metarhizium anisopliae were evaluated for their pathogencity against the larvae and adults of Rhynchophorus ferrugineus under laboratory conditions. Red palm weevil stages were collected from the infested palm trees, Al-Hasa Governorate, KSA, and reared on pieces of sugarcane. Three concentrations of each fungi spores were prepared, 1×10⁷, 1×10⁸ and 1×10⁹ spores/ml. Adults of R. ferrugineus (male and female) and larvae were treated by dipping and injection bioassay techniques. The control treatment was treated with sterilized water. After treatments, insects were transferred to jars containing sugarcane. Insects were observed for three weeks and the percent of mortality recorded. The results showed variation in mortality for different stages. Mortality percentages were 40, 55, and 60 for male, female and larvae, respectively, at a concentration of 1×10⁷ spore/ml of B. bassiana when insects were treated by dipping technique. Mortality reached 80, 85 and 85% for male, female and larvae, respectively when treated by injection at the same concentration. Mortality percentages were 35, 50, and 60 for male, female and larvae, respectively at a concentration of 1×10⁷ spore/ml of M. anisopliae when insects were treated by dipping. The mortality reached 70, 60, and 70% for the previous stages when treated by injection at the same concentration after ten days of observation. The percent of mortality increased with increasing concentration of fungus spores. The percent of mortality reached 70 and 80 for female and male when contaminated males were transferred to jars containing untreated females after 17 days of transfer. The percent of mortality reached 10% in the control treatment during that period.