MORTALITY EFFECTS OF SIX DIFFERENT ENTOMOPATHOGENIC FUNGI STRAINS ON RICE WEEVIL, SITOPHILUS ORYZAE (L.) (COLEOPTERA: CURCULIONIDAE)

Abstract

The rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), is one of the most destructive pests on the stored rice throughout the world. In present study, the mortality effects of six entomopathogenic isolates of Beauveria bassiana (BB-4984), Paecilomyces farinosus (PAF-2538), Isaria fumosorosea (ISFUM-4501), Isaria farinosa (IFA-3580), Lecanicillium muscarium (LECMUS-972) and Lecanicillium muscarium (LECMUS-5128), were tested against the adults of S. oryzae under 85 +/- 5% R.H. and with 1x10(5) and 1x10(7) conidial concentrations (ml(-1)). Treatments were carried out in a climate chamber with 27 +/- 1 degrees C and 16 h. light and 8 h. dark photoperiods. Each concentration was replicated three times, and the mortality percentages were monitored on the 2nd, 4th, 6th, 8th and 10th days of incubation. Lecanicillium muscarium isolate extracted from Mycotal (Koppert, NL) was used as the commercial (positive) control, while Tween20+sterile water was used as control in this study. Results revealed that I. farinosa (IFA-3580) yielded the greatest mortality rates (between 62.60 - 90.60%) for S. oryzae adults under 85 +/- 5% R.H. and 1x10(7) conidial concentrations (ml(-1)) during incubation, but L. muscarium (LECMUS-5128) yielded the least mortality rates (between 26.60 - 73.30%, except B. bassiana (BB-4984) and L. muscarium (LECMUS-972) on the 8th day) the same conditions and with 1x10(5) dose on loth days. As compared to control treatments, six entomopathogenic fungi isolates led to a significant amount of mortality on S. oryzae adults at all doses and periods. Therefore, they might have a potential effect in biological control of S. oryzae adults due to their strong entomopathogenic activity.