Essential oil of ocotea odorifera: An alternative against sitophilus zeamais

Nowadays, the maize weevil Sitophilus zeamais-Motsch 1855 is the most relevant pest found during storage of maize grains. Aiming at protecting the agricultural crops, high amounts of synthetic pesticides are used around the world. In this sense, this work aimed at evaluating the insecticidal and repellent effect of essential oil of Ocotea odorifera (Vellozo) Rohwer (Lauraceae) (O. odorifera (sassafras)) leaves against the maize weevil in maize grains. The essential oil's chemical composition showed that sassafras contains camphor (43%) and safrole (42%) as major compounds. Our results show that sassafras oil was insecticidal and repellent to maize weevil. About 100% mortality was achieved using a concentration of 0.32μl cm-2, after 24 h of exposure. The LD50 value was 14.1μl or 0.09μl cm-2 and the study of the effect on insect mortality at the lethal doses (LD50) showed that after 72h mortality was 100%. The values of the preference index varied from -0.39 (0.065μl cm-2) to -0.63 (0.659μl cm-2), demonstrating that the plant oil presents repellent activity. The repellency bioassay simulating small bins showed the repellent effect level from 0.64 (0.36μl cm-3) to 0.94 (2.9μl cm-3). The essential oil of sassafras presented insecticidal and repellency against maize weevil. Although from an economical point of view synthetic chemicals are still more frequently used as repellents, natural products (essential oils) have the potential to provide efficient and safer repellents for humans and the environment.