BIOACTIVITY OF OIL PALM, ELAEIS GUINEENSIS (JACQ) (ARAECEAE) KERNEL OILS AGAINST SITOPHILUS ORYZAE (L.) (COLEOPTERA: CURCULIONIDAE): EXTRACTION METHODS AND TEMPERATURE EFFECT

Local and solvent-extracted palm kernel oils (LPKO and SPKO) were screened for bioactivity against Sitophilus oryzae (L.) in unpolished rice (Oryza sativa (L.)). Both oils were tested for toxicity to adults, and progeny inhibition at 0, 0.5, 1.0, 1.5, and 2.0 ml/50g of rice. Toxicity of mixtures of the oils: 1:1, 2:1(LPKO: SPKO), and 2:1 (SPKO: LPKO) was evaluated for synergism between LPKO and SPKO. Effect of temperature variation on bioactivity of individual oils was observed at 26, 28, 30, and 32oC. Both oils killed adults, and inhibited F1 progeny of S. oryzae. LPKO was more effective in killing adults and inhibiting F1 progeny than SPKO. The 1.5ml/50g dose of LPKO caused 100% mortality at 48 h post-treatment. A 100% mortality was obtained with SPKO but at 2.0ml/50g in 72 h post-treatment. The order of toxicity of mixtures of PKOs was 2:1 LPKO: SPKO > 2:1 LPKO: SPKO > 2:1 SPKO: LPKO. Percent adult mortalities were higher in oil-mixtures than in individual oils which indicates synergistic effect of LPKO on SPKO. Toxicities of both oils increased with increasing temperatures. The results showed that LPKO possess some components of higher insecticidal potential, which if explored, could be useful in Integrated Pest Management of S. oryzae. Keywords: Adult emergence, extraction methods, palm kernel oil, progeny inhibition, temperature, toxicity.